Add set_sprite_clip_def for pre-resolved clip switches

Resolve batching_test.odin by keeping master tests and the MAX_SPRITES guard test.

Makefile

@@ -1,7 +1,7 @@
-.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all bake toad hello_sprite crowd camera_sandbox clips check test help
+.PHONY: shaders-vulkan shaders-d3d12 shaders-metal shaders-all bake toad hello_sprite crowd crowd_batch crowd_overdraw clip_thrash camera_sandbox clips check test help
 .PHONY: flame flame-build flame-record flame-svg flame-report flame-tools
 
-# Flamegraph profiling (needs: pacman -S perf). Example: make flame  or  make flame FLAME_EXAMPLE=toad
+# Flamegraph profiling (needs: pacman -S perf). Example: make flame  or  make flame FLAME_EXAMPLE=crowd_batch
 FLAME_EXAMPLE ?= crowd
 FLAME_BIN := $(FLAME_EXAMPLE)_perf
 FLAMEGRAPH_DIR ?= tools/FlameGraph
@@ -24,6 +24,9 @@ help:
 	@echo "  toad             Run the toad example (full demo)"
 	@echo "  hello_sprite     Minimal load + draw"
 	@echo "  crowd            Many sprites, one Character_Data"
+	@echo "  crowd_batch      Multi-texture batching stress (two toad loads)"
+	@echo "  crowd_overdraw   Stacked sprites overdraw stress"
+	@echo "  clip_thrash      Per-frame idle/walk clip flip stress"
 	@echo "  camera_sandbox   Pan camera / Space toggles follow"
 	@echo "  clips            Keys 1/2 switch idle/walk"
 	@echo "  flame            Build+record+SVG+JPG+text report (FLAME_EXAMPLE=$(FLAME_EXAMPLE))"
@@ -54,6 +57,9 @@ check:
 	odin check examples/toad -collection:pkg=.
 	odin check examples/hello_sprite -collection:pkg=.
 	odin check examples/crowd -collection:pkg=.
+	odin check examples/crowd_batch -collection:pkg=.
+	odin check examples/crowd_overdraw -collection:pkg=.
+	odin check examples/clip_thrash -collection:pkg=.
 	odin check examples/camera_sandbox -collection:pkg=.
 	odin check examples/clips -collection:pkg=.
 
@@ -66,6 +72,15 @@ hello_sprite:
 crowd:
 	odin run examples/crowd -collection:pkg=.
 
+crowd_batch:
+	odin run examples/crowd_batch -collection:pkg=.
+
+crowd_overdraw:
+	odin run examples/crowd_overdraw -collection:pkg=.
+
+clip_thrash:
+	odin run examples/clip_thrash -collection:pkg=.
+
 camera_sandbox:
 	odin run examples/camera_sandbox -collection:pkg=.
 

engine/animation_test.odin

@@ -118,6 +118,63 @@ set_sprite_clip_switch_and_guards :: proc(t: ^testing.T) {
 	testing.expect_value(t, sprite.time, f32(0.09))
 }
 
+@(test)
+set_sprite_clip_caches_clip_def :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	sprite := spawn_sprite(&data, {}, "idle", 0)
+	testing.expect(t, sprite.has_clip, "spawn should cache a valid clip")
+	testing.expect_value(t, sprite.clip, "idle")
+	testing.expect(t, sprite.clip_def.loop, "idle clip loops")
+	testing.expect_value(t, sprite.clip_def.fps, f32(10))
+	testing.expect_value(t, len(sprite.clip_def.frames), 3)
+
+	set_sprite_clip(&sprite, "once")
+	testing.expect(t, sprite.has_clip, "switch should refresh cache")
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect(t, !sprite.clip_def.loop, "once clip does not loop")
+	testing.expect_value(t, sprite.clip_def.fps, f32(10))
+	testing.expect_value(t, len(sprite.clip_def.frames), 3)
+
+	set_sprite_clip(&sprite, "nope")
+	testing.expect(t, sprite.has_clip, "bad clip must leave cache intact")
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect(t, !sprite.clip_def.loop, "cached once clip preserved")
+	testing.expect_value(t, len(sprite.clip_def.frames), 3)
+}
+
+@(test)
+set_sprite_clip_def_applies_and_guards :: proc(t: ^testing.T) {
+	data := make_test_character()
+	defer destroy_test_character(&data)
+
+	sprite := spawn_sprite(&data, {}, "idle", 0)
+	sprite.frame = 2
+	sprite.time = 0.05
+
+	once := data.def.clips["once"]
+	set_sprite_clip_def(&sprite, "once", once)
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect(t, sprite.has_clip, "def apply should mark clip present")
+	testing.expect_value(t, sprite.frame, 0)
+	testing.expect_value(t, sprite.time, f32(0))
+	testing.expect(t, !sprite.clip_def.loop, "once clip does not loop")
+	testing.expect_value(t, len(sprite.clip_def.frames), 3)
+
+	sprite.frame = 1
+	sprite.time = 0.09
+	set_sprite_clip_def(&sprite, "once", once)
+	testing.expect_value(t, sprite.frame, 1)
+	testing.expect_value(t, sprite.time, f32(0.09))
+
+	set_sprite_clip_def(&sprite, "empty", Clip_Def{loop = true, fps = 10, frames = nil})
+	testing.expect_value(t, sprite.clip, "once")
+	testing.expect_value(t, sprite.frame, 1)
+
+	set_sprite_clip_def(nil, "once", once)
+}
+
 @(test)
 spawn_sprite_valid_and_invalid :: proc(t: ^testing.T) {
 	data := make_test_character()

engine/app.odin

@@ -11,13 +11,20 @@ Vertex :: struct {
 }
 
 SPRITE_VERT_COUNT :: 6
-MAX_SPRITES :: 1012 // 1000 game sprites + FPS overlay glyphs
+MAX_SPRITES :: 128
 SPRITE_VERTS_SIZE :: SPRITE_VERT_COUNT * size_of(Vertex)
 VERTEX_BUFFER_SIZE :: MAX_SPRITES * SPRITE_VERTS_SIZE
 
 Queued_Sprite :: struct {
+	texture:     ^sdl.GPUTexture,
+	verts:       [SPRITE_VERT_COUNT]Vertex,
+	batch_group: u32, // 0 = strict order; nonzero = caller permits regrouping
+}
+
+Draw_Batch :: struct {
+	start:   int,
+	count:   int,
 	texture: ^sdl.GPUTexture,
-	verts:   [SPRITE_VERT_COUNT]Vertex,
 }
 
 App :: struct {
@@ -36,12 +43,6 @@ App :: struct {
 	draw_list:         [dynamic]Queued_Sprite,
 	clear_color:       sdl.FColor,
 	camera:            Camera,
-	show_fps:          bool,
-	fps_texture:       ^sdl.GPUTexture,
-	fps_smooth:        f32,
-	fps_display:       int,
-	fps_last_time:     f64,
-	fps_update_accum:  f32,
 }
 
 Shader_Backend :: enum {
@@ -71,7 +72,7 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 	}
 
 	requested: sdl.GPUShaderFormat = {.SPIRV, .DXIL, .MSL}
-	app.device = sdl.CreateGPUDevice(requested, true, nil)
+	app.device = sdl.CreateGPUDevice(requested, false, nil)
 	if app.device == nil {
 		fmt.eprintfln("CreateGPUDevice failed: %s", sdl.GetError())
 		return false
@@ -82,6 +83,10 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 		return false
 	}
 
+	if !sdl.SetGPUAllowedFramesInFlight(app.device, 3) {
+		fmt.eprintfln("SetGPUAllowedFramesInFlight failed: %s", sdl.GetError())
+	}
+
 	// Prefer uncapped present for profiling; fall back if unsupported.
 	present := sdl.GPUPresentMode.VSYNC
 	if sdl.WindowSupportsGPUPresentMode(app.device, app.window, .IMMEDIATE) {
@@ -146,10 +151,6 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 
 	app.camera = camera_default()
 
-	if !fps_overlay_init(app) {
-		fmt.eprintfln("fps overlay init failed; continuing without on-screen FPS")
-	}
-
 	return true
 }
 
@@ -162,8 +163,6 @@ shutdown :: proc(app: ^App) {
 			fmt.eprintfln("WaitForGPUIdle failed")
 		}
 
-		fps_overlay_shutdown(app)
-
 		if app.transfer_buffer != nil {
 			sdl.ReleaseGPUTransferBuffer(app.device, app.transfer_buffer)
 		}
@@ -207,8 +206,6 @@ events :: proc() -> bool {
 }
 
 begin_frame :: proc(app: ^App, clear_color: sdl.FColor = {0.12, 0.12, 0.16, 1}) {
-	fps_overlay_begin_frame(app)
-
 	clear(&app.draw_list)
 	app.clear_color = clear_color
 	app.render_pass = nil
@@ -255,10 +252,12 @@ end_frame :: proc(app: ^App) {
 		return
 	}
 
-	fps_overlay_queue(app)
-
 	n := len(app.draw_list)
+	batches: [dynamic]Draw_Batch
+	defer delete(batches)
 	if n > 0 {
+		prepare_draw_batches(app.draw_list[:], &batches)
+
 		map_ptr := sdl.MapGPUTransferBuffer(app.device, app.transfer_buffer, false)
 		if map_ptr == nil {
 			fmt.eprintfln("MapGPUTransferBuffer failed: %s", sdl.GetError())
@@ -302,26 +301,20 @@ end_frame :: proc(app: ^App) {
 	app.render_pass = sdl.BeginGPURenderPass(cmd, &color_info, 1, nil)
 	sdl.BindGPUGraphicsPipeline(app.render_pass, app.pipeline)
 
-	i := 0
-	for i < n {
-		run := texture_run_len(app.draw_list[:], i)
-		q0 := app.draw_list[i]
-
+	for batch in batches {
 		sampler_binding := sdl.GPUTextureSamplerBinding {
-			texture = q0.texture,
+			texture = batch.texture,
 			sampler = app.sampler,
 		}
 		sdl.BindGPUFragmentSamplers(app.render_pass, 0, &sampler_binding, 1)
 
 		vb_binding := sdl.GPUBufferBinding {
 			buffer = app.vertex_buffer,
-			offset = u32(i * SPRITE_VERTS_SIZE),
+			offset = u32(batch.start * SPRITE_VERTS_SIZE),
 		}
 		sdl.BindGPUVertexBuffers(app.render_pass, 0, &vb_binding, 1)
 
-		sdl.DrawGPUPrimitives(app.render_pass, u32(run * SPRITE_VERT_COUNT), 1, 0, 0)
-
-		i += run
+		sdl.DrawGPUPrimitives(app.render_pass, u32(batch.count * SPRITE_VERT_COUNT), 1, 0, 0)
 	}
 	sdl.EndGPURenderPass(app.render_pass)
 	app.render_pass = nil
@@ -470,3 +463,119 @@ texture_run_len :: proc(list: []Queued_Sprite, start: int) -> int {
 
 	return n
 }
+
+texture_run_count :: proc(list: []Queued_Sprite) -> int {
+	if len(list) == 0 do return 0
+	count := 0
+	i := 0
+	for i < len(list) {
+		run := texture_run_len(list, i)
+		count += 1
+		i += run
+	}
+	return count
+}
+
+prepare_draw_batches :: proc(list: []Queued_Sprite, batches: ^[dynamic]Draw_Batch) {
+	clear(batches)
+	group_texture_runs(list)
+	i := 0
+	for i < len(list) {
+		run := texture_run_len(list, i)
+		append(batches, Draw_Batch{start = i, count = run, texture = list[i].texture})
+		i += run
+	}
+}
+
+// Within each contiguous nonzero batch_group, stably sort by texture so
+// consecutive same-texture sprites become one draw. Group 0 and group
+// boundaries are never crossed.
+group_texture_runs :: proc(list: []Queued_Sprite) {
+	start := 0
+	for start < len(list) {
+		group := list[start].batch_group
+		if group == 0 {
+			start += 1
+			continue
+		}
+
+		end := start + 1
+		for end < len(list) && list[end].batch_group == group {
+			end += 1
+		}
+
+		stable_group_by_texture(list[start:end])
+		start = end
+	}
+}
+
+// Stably orders window by texture pointer. Fast path for 1–2 textures
+// (common); insertion sort for 3+.
+stable_group_by_texture :: proc(window: []Queued_Sprite) {
+	n := len(window)
+	if n <= 1 do return
+
+	already := true
+	for i in 1 ..< n {
+		if uintptr(window[i].texture) < uintptr(window[i - 1].texture) {
+			already = false
+			break
+		}
+	}
+	if already do return
+
+	first := uintptr(window[0].texture)
+	second: uintptr
+	has_second := false
+	third := false
+	for i in 1 ..< n {
+		t := uintptr(window[i].texture)
+		if t == first do continue
+		if !has_second {
+			second = t
+			has_second = true
+			continue
+		}
+		if t != second {
+			third = true
+			break
+		}
+	}
+
+	if !has_second do return
+
+	if third {
+		for i in 1 ..< n {
+			item := window[i]
+			j := i
+			for j > 0 {
+				if uintptr(window[j - 1].texture) <= uintptr(item.texture) {
+					break
+				}
+				window[j] = window[j - 1]
+				j -= 1
+			}
+			window[j] = item
+		}
+		return
+	}
+
+	lo, hi := first, second
+	if lo > hi do lo, hi = hi, lo
+
+	tmp: [MAX_SPRITES]Queued_Sprite
+	w := 0
+	for q in window {
+		if uintptr(q.texture) == lo {
+			tmp[w] = q
+			w += 1
+		}
+	}
+	for q in window {
+		if uintptr(q.texture) == hi {
+			tmp[w] = q
+			w += 1
+		}
+	}
+	copy(window, tmp[:w])
+}

engine/batching_test.odin

@@ -7,6 +7,18 @@ fake_tex :: proc(id: uintptr) -> ^sdl.GPUTexture {
 	return cast(^sdl.GPUTexture)id
 }
 
+queued :: proc(tex_id: uintptr, group: u32, marker: f32) -> Queued_Sprite {
+	q: Queued_Sprite
+	q.texture = fake_tex(tex_id)
+	q.batch_group = group
+	q.verts[0].pos = {marker, 0}
+	return q
+}
+
+marker_of :: proc(q: Queued_Sprite) -> f32 {
+	return q.verts[0].pos.x
+}
+
 @(test)
 texture_run_len_empty_or_oob :: proc(t: ^testing.T) {
 	testing.expect_value(t, texture_run_len(nil, 0), 0)
@@ -62,3 +74,356 @@ texture_run_len_all_different :: proc(t: ^testing.T) {
 	testing.expect_value(t, texture_run_len(list, 1), 1)
 	testing.expect_value(t, texture_run_len(list, 2), 1)
 }
+
+@(test)
+group_texture_runs_strict_order_unchanged :: proc(t: ^testing.T) {
+	// Group 0 alternates textures; sorting must not reorder (alpha order).
+	list := []Queued_Sprite {
+		queued(2, 0, 1),
+		queued(1, 0, 2),
+		queued(2, 0, 3),
+		queued(1, 0, 4),
+	}
+	before_runs := texture_run_count(list)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), before_runs)
+	testing.expect_value(t, marker_of(list[0]), f32(1))
+	testing.expect_value(t, marker_of(list[1]), f32(2))
+	testing.expect_value(t, marker_of(list[2]), f32(3))
+	testing.expect_value(t, marker_of(list[3]), f32(4))
+}
+
+@(test)
+group_texture_runs_reduces_runs_inside_group :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(2, 1, 1),
+		queued(1, 1, 2),
+		queued(2, 1, 3),
+		queued(1, 1, 4),
+	}
+	testing.expect_value(t, texture_run_count(list), 4)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 2)
+	testing.expect(t, list[0].texture == fake_tex(1), "lower texture pointer first")
+	testing.expect(t, list[1].texture == fake_tex(1), "same texture run")
+	testing.expect(t, list[2].texture == fake_tex(2), "second texture run")
+	testing.expect(t, list[3].texture == fake_tex(2), "second texture run cont")
+}
+
+@(test)
+group_texture_runs_stable_same_texture :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(2, 1, 10),
+		queued(1, 1, 20),
+		queued(2, 1, 30),
+		queued(1, 1, 40),
+	}
+	group_texture_runs(list)
+	// Same-texture relative order preserved (stable sort).
+	testing.expect_value(t, marker_of(list[0]), f32(20))
+	testing.expect_value(t, marker_of(list[1]), f32(40))
+	testing.expect_value(t, marker_of(list[2]), f32(10))
+	testing.expect_value(t, marker_of(list[3]), f32(30))
+}
+
+@(test)
+group_texture_runs_respects_group_boundaries :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(2, 1, 1),
+		queued(1, 1, 2),
+		queued(2, 0, 3), // strict barrier
+		queued(1, 2, 4),
+		queued(2, 2, 5),
+	}
+	group_texture_runs(list)
+	testing.expect_value(t, marker_of(list[2]), f32(3)) // barrier stays put
+	testing.expect(t, list[0].texture == fake_tex(1))
+	testing.expect(t, list[1].texture == fake_tex(2))
+	testing.expect(t, list[3].texture == fake_tex(1))
+	testing.expect(t, list[4].texture == fake_tex(2))
+	testing.expect_value(t, list[0].batch_group, u32(1))
+	testing.expect_value(t, list[1].batch_group, u32(1))
+	testing.expect_value(t, list[2].batch_group, u32(0))
+	testing.expect_value(t, list[3].batch_group, u32(2))
+	testing.expect_value(t, list[4].batch_group, u32(2))
+}
+
+@(test)
+group_texture_runs_does_not_merge_across_different_groups :: proc(t: ^testing.T) {
+	// Adjacent nonzero groups with different ids must not merge runs across.
+	list := []Queued_Sprite {
+		queued(1, 1, 1),
+		queued(2, 1, 2),
+		queued(1, 2, 3),
+		queued(2, 2, 4),
+	}
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 4)
+	testing.expect_value(t, list[0].batch_group, u32(1))
+	testing.expect_value(t, list[1].batch_group, u32(1))
+	testing.expect_value(t, list[2].batch_group, u32(2))
+	testing.expect_value(t, list[3].batch_group, u32(2))
+}
+
+@(test)
+group_texture_runs_empty :: proc(t: ^testing.T) {
+	list := []Queued_Sprite{}
+	testing.expect_value(t, texture_run_count(list), 0)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 0)
+}
+
+@(test)
+group_texture_runs_already_optimal :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(1, 1, 10),
+		queued(1, 1, 20),
+		queued(2, 1, 30),
+		queued(2, 1, 40),
+	}
+	testing.expect_value(t, texture_run_count(list), 2)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 2)
+	testing.expect_value(t, marker_of(list[0]), f32(10))
+	testing.expect_value(t, marker_of(list[1]), f32(20))
+	testing.expect_value(t, marker_of(list[2]), f32(30))
+	testing.expect_value(t, marker_of(list[3]), f32(40))
+}
+
+@(test)
+group_texture_runs_alternating_many_stable :: proc(t: ^testing.T) {
+	// Characterization: large alternating group must collapse to two runs
+	// while preserving same-texture submission order (markers).
+	N :: 64
+	list := make([]Queued_Sprite, N)
+	defer delete(list)
+	for i in 0 ..< N {
+		tex: uintptr = 2 if (i % 2) == 0 else 1
+		list[i] = queued(tex, 1, f32(i + 1))
+	}
+	testing.expect_value(t, texture_run_count(list), N)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 2)
+	testing.expect(t, list[0].texture == fake_tex(1))
+	testing.expect(t, list[N / 2 - 1].texture == fake_tex(1))
+	testing.expect(t, list[N / 2].texture == fake_tex(2))
+	testing.expect(t, list[N - 1].texture == fake_tex(2))
+	for i in 0 ..< N / 2 {
+		testing.expect_value(t, marker_of(list[i]), f32(2 * i + 2)) // odd markers: 2,4,...,N
+		testing.expect_value(t, marker_of(list[N / 2 + i]), f32(2 * i + 1)) // even markers: 1,3,...,N-1
+	}
+}
+
+@(test)
+group_texture_runs_three_textures_stable :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(3, 1, 1),
+		queued(1, 1, 2),
+		queued(2, 1, 3),
+		queued(3, 1, 4),
+		queued(1, 1, 5),
+		queued(2, 1, 6),
+	}
+	testing.expect_value(t, texture_run_count(list), 6)
+	group_texture_runs(list)
+	testing.expect_value(t, texture_run_count(list), 3)
+	testing.expect_value(t, marker_of(list[0]), f32(2))
+	testing.expect_value(t, marker_of(list[1]), f32(5))
+	testing.expect_value(t, marker_of(list[2]), f32(3))
+	testing.expect_value(t, marker_of(list[3]), f32(6))
+	testing.expect_value(t, marker_of(list[4]), f32(1))
+	testing.expect_value(t, marker_of(list[5]), f32(4))
+}
+
+@(test)
+group_texture_runs_noncontiguous_same_group_id :: proc(t: ^testing.T) {
+	// Same nonzero id split by group 0: each window regroups alone.
+	list := []Queued_Sprite {
+		queued(2, 1, 1),
+		queued(1, 1, 2),
+		queued(2, 0, 3),
+		queued(2, 1, 4),
+		queued(1, 1, 5),
+	}
+	group_texture_runs(list)
+	testing.expect_value(t, marker_of(list[2]), f32(3))
+	testing.expect(t, list[0].texture == fake_tex(1))
+	testing.expect(t, list[1].texture == fake_tex(2))
+	testing.expect_value(t, list[2].batch_group, u32(0))
+	testing.expect(t, list[3].texture == fake_tex(1))
+	testing.expect(t, list[4].texture == fake_tex(2))
+	testing.expect_value(t, list[0].batch_group, u32(1))
+	testing.expect_value(t, list[1].batch_group, u32(1))
+	testing.expect_value(t, list[3].batch_group, u32(1))
+	testing.expect_value(t, list[4].batch_group, u32(1))
+}
+
+make_test_draw_app :: proc() -> App {
+	app: App
+	app.cmd = cast(^sdl.GPUCommandBuffer)uintptr(1)
+	app.swapchain_texture = fake_tex(99)
+	app.swapchain_w = 800
+	app.swapchain_h = 600
+	app.camera = camera_default()
+	app.draw_list = make([dynamic]Queued_Sprite)
+	return app
+}
+
+destroy_test_draw_app :: proc(app: ^App) {
+	if app == nil do return
+	delete(app.draw_list)
+	app^ = {}
+}
+
+make_test_draw_character :: proc() -> Character_Data {
+	data: Character_Data
+	data.texture = fake_tex(42)
+	data.width = 100
+	data.height = 100
+	data.def.pivot = {0.5, 1.0}
+	data.def.clips = make(map[string]Clip_Def)
+	frames := make([]Frame_Def, 1)
+	frames[0] = Frame_Def {
+		rect        = {0, 0, 10, 10},
+		source_size = {10, 10},
+		trim_offset = {0, 0},
+	}
+	data.def.clips["idle"] = Clip_Def {
+		loop   = true,
+		fps    = 10,
+		frames = frames,
+	}
+	return data
+}
+
+destroy_test_draw_character :: proc(data: ^Character_Data) {
+	if data == nil do return
+	keys := make([dynamic]string, context.temp_allocator)
+	for key, clip in data.def.clips {
+		delete(clip.frames)
+		append(&keys, key)
+	}
+	for key in keys {
+		delete_key(&data.def.clips, key)
+	}
+	delete(data.def.clips)
+	data^ = {}
+}
+
+@(test)
+draw_sprite_stamps_batch_group_zero :: proc(t: ^testing.T) {
+	app := make_test_draw_app()
+	defer destroy_test_draw_app(&app)
+	data := make_test_draw_character()
+	defer destroy_test_draw_character(&data)
+
+	sprite := spawn_sprite(&data, {100, 200}, "idle", 0)
+	draw_sprite(&app, &sprite)
+
+	testing.expect_value(t, len(app.draw_list), 1)
+	testing.expect_value(t, app.draw_list[0].batch_group, u32(0))
+	testing.expect(t, app.draw_list[0].texture == data.texture)
+}
+
+@(test)
+draw_sprite_at_max_sprites_does_not_append :: proc(t: ^testing.T) {
+	app := make_test_draw_app()
+	defer destroy_test_draw_app(&app)
+	data := make_test_draw_character()
+	defer destroy_test_draw_character(&data)
+
+	for _ in 0 ..< MAX_SPRITES {
+		append(&app.draw_list, Queued_Sprite{texture = data.texture})
+	}
+	testing.expect_value(t, len(app.draw_list), MAX_SPRITES)
+
+	sprite := spawn_sprite(&data, {100, 200}, "idle", 0)
+	draw_sprite(&app, &sprite)
+
+	testing.expect_value(t, len(app.draw_list), MAX_SPRITES)
+}
+
+@(test)
+draw_sprite_batched_stamps_batch_group :: proc(t: ^testing.T) {
+	app := make_test_draw_app()
+	defer destroy_test_draw_app(&app)
+	data := make_test_draw_character()
+	defer destroy_test_draw_character(&data)
+
+	sprite := spawn_sprite(&data, {100, 200}, "idle", 0)
+	draw_sprite_batched(&app, &sprite, 7)
+
+	testing.expect_value(t, len(app.draw_list), 1)
+	testing.expect_value(t, app.draw_list[0].batch_group, u32(7))
+	testing.expect(t, app.draw_list[0].texture == data.texture)
+}
+
+@(test)
+draw_sprite_batched_guards_leave_list_unchanged :: proc(t: ^testing.T) {
+	app := make_test_draw_app()
+	defer destroy_test_draw_app(&app)
+	data := make_test_draw_character()
+	defer destroy_test_draw_character(&data)
+	sprite := spawn_sprite(&data, {100, 200}, "idle", 0)
+
+	app.cmd = nil
+	draw_sprite_batched(&app, &sprite, 1)
+	testing.expect_value(t, len(app.draw_list), 0)
+	app.cmd = cast(^sdl.GPUCommandBuffer)uintptr(1)
+
+	app.swapchain_texture = nil
+	draw_sprite_batched(&app, &sprite, 1)
+	testing.expect_value(t, len(app.draw_list), 0)
+	app.swapchain_texture = fake_tex(99)
+
+	draw_sprite_batched(&app, nil, 1)
+	testing.expect_value(t, len(app.draw_list), 0)
+
+	no_data := sprite
+	no_data.data = nil
+	draw_sprite_batched(&app, &no_data, 1)
+	testing.expect_value(t, len(app.draw_list), 0)
+
+	no_tex := sprite
+	tex_data := data
+	tex_data.texture = nil
+	no_tex.data = &tex_data
+	draw_sprite_batched(&app, &no_tex, 1)
+	testing.expect_value(t, len(app.draw_list), 0)
+}
+
+@(test)
+prepare_draw_batches_regroups_then_plans_runs :: proc(t: ^testing.T) {
+	list := []Queued_Sprite {
+		queued(2, 1, 1),
+		queued(1, 1, 2),
+		queued(2, 1, 3),
+		queued(1, 1, 4),
+		queued(3, 0, 5),
+		queued(1, 0, 6),
+	}
+	batches := make([dynamic]Draw_Batch)
+	defer delete(batches)
+
+	prepare_draw_batches(list, &batches)
+
+	testing.expect_value(t, len(batches), 4)
+	testing.expect_value(t, batches[0].start, 0)
+	testing.expect_value(t, batches[0].count, 2)
+	testing.expect(t, batches[0].texture == fake_tex(1))
+	testing.expect_value(t, batches[1].start, 2)
+	testing.expect_value(t, batches[1].count, 2)
+	testing.expect(t, batches[1].texture == fake_tex(2))
+	testing.expect_value(t, batches[2].start, 4)
+	testing.expect_value(t, batches[2].count, 1)
+	testing.expect(t, batches[2].texture == fake_tex(3))
+	testing.expect_value(t, batches[3].start, 5)
+	testing.expect_value(t, batches[3].count, 1)
+	testing.expect(t, batches[3].texture == fake_tex(1))
+
+	// Group 0 submission order preserved.
+	testing.expect_value(t, marker_of(list[4]), f32(5))
+	testing.expect_value(t, marker_of(list[5]), f32(6))
+	testing.expect_value(t, list[4].batch_group, u32(0))
+	testing.expect_value(t, list[5].batch_group, u32(0))
+}

engine/fps_overlay.odin

@@ -1,279 +0,0 @@
-package engine
-
-import "core:fmt"
-import "core:mem"
-import sdl "vendor:sdl3"
-
-// Enough for an 8-digit rate plus " FPS".
-FPS_OVERLAY_MAX_GLYPHS :: 12
-FPS_GLYPH_W :: 5
-FPS_GLYPH_H :: 7
-FPS_CELL_W :: 6
-FPS_CELL_H :: 8
-FPS_ATLAS_COLS :: 16
-FPS_SCALE :: 2
-FPS_MARGIN :: 8
-FPS_UPDATE_INTERVAL :: 0.25
-
-// Glyph indices in the debug atlas.
-FPS_GLYPH_DIGIT_0 :: 0
-FPS_GLYPH_F :: 10
-FPS_GLYPH_P :: 11
-FPS_GLYPH_S :: 12
-FPS_GLYPH_SPACE :: 13
-
-// 5x7 bitmaps (MSB = left). Digits 0-9, then F/P/S/space.
-@(private)
-fps_glyph_rows := [14][7]u8 {
-	{0x0E, 0x11, 0x13, 0x15, 0x19, 0x11, 0x0E}, // 0
-	{0x04, 0x0C, 0x04, 0x04, 0x04, 0x04, 0x0E}, // 1
-	{0x0E, 0x11, 0x01, 0x06, 0x08, 0x10, 0x1F}, // 2
-	{0x0E, 0x11, 0x01, 0x06, 0x01, 0x11, 0x0E}, // 3
-	{0x02, 0x06, 0x0A, 0x12, 0x1F, 0x02, 0x02}, // 4
-	{0x1F, 0x10, 0x1E, 0x01, 0x01, 0x11, 0x0E}, // 5
-	{0x06, 0x08, 0x10, 0x1E, 0x11, 0x11, 0x0E}, // 6
-	{0x1F, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08}, // 7
-	{0x0E, 0x11, 0x11, 0x0E, 0x11, 0x11, 0x0E}, // 8
-	{0x0E, 0x11, 0x11, 0x0F, 0x01, 0x02, 0x0C}, // 9
-	{0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x10}, // F
-	{0x1E, 0x11, 0x11, 0x1E, 0x10, 0x10, 0x10}, // P
-	{0x0F, 0x10, 0x10, 0x0E, 0x01, 0x01, 0x1E}, // S
-	{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // space
-}
-
-set_show_fps :: proc(app: ^App, enabled: bool) {
-	if app == nil do return
-	app.show_fps = enabled
-}
-
-@(private)
-fps_overlay_init :: proc(app: ^App) -> bool {
-	app.show_fps = true
-	app.fps_smooth = 0
-	app.fps_display = 0
-	app.fps_last_time = 0
-	app.fps_update_accum = 0
-	app.fps_texture = nil
-
-	atlas_w := FPS_ATLAS_COLS * FPS_CELL_W
-	atlas_h := FPS_CELL_H
-	pixels := make([]u8, atlas_w * atlas_h * 4)
-	defer delete(pixels)
-
-	for gi in 0 ..< len(fps_glyph_rows) {
-		gx := gi * FPS_CELL_W
-		rows := fps_glyph_rows[gi]
-		for row in 0 ..< FPS_GLYPH_H {
-			bits := rows[row]
-			for col in 0 ..< FPS_GLYPH_W {
-				on := (bits >> u8(FPS_GLYPH_W - 1 - col)) & 1 == 1
-				px := gx + col
-				py := row
-				i := (py * atlas_w + px) * 4
-				if on {
-					pixels[i + 0] = 255
-					pixels[i + 1] = 255
-					pixels[i + 2] = 255
-					pixels[i + 3] = 255
-				}
-			}
-		}
-	}
-
-	app.fps_texture = sdl.CreateGPUTexture(
-		app.device,
-		{
-			type = .D2,
-			format = .R8G8B8A8_UNORM,
-			usage = {.SAMPLER},
-			width = u32(atlas_w),
-			height = u32(atlas_h),
-			layer_count_or_depth = 1,
-			num_levels = 1,
-			sample_count = ._1,
-		},
-	)
-	if app.fps_texture == nil {
-		fmt.eprintfln("FPS overlay CreateGPUTexture failed: %s", sdl.GetError())
-		return false
-	}
-
-	upload_size := atlas_w * atlas_h * 4
-	tbuf := sdl.CreateGPUTransferBuffer(app.device, {usage = .UPLOAD, size = u32(upload_size)})
-	if tbuf == nil {
-		fmt.eprintfln("FPS overlay CreateGPUTransferBuffer failed: %s", sdl.GetError())
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-		app.fps_texture = nil
-		return false
-	}
-	defer sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
-
-	map_ptr := sdl.MapGPUTransferBuffer(app.device, tbuf, false)
-	if map_ptr == nil {
-		fmt.eprintfln("FPS overlay MapGPUTransferBuffer failed: %s", sdl.GetError())
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-		app.fps_texture = nil
-		return false
-	}
-	mem.copy(map_ptr, raw_data(pixels), upload_size)
-	sdl.UnmapGPUTransferBuffer(app.device, tbuf)
-
-	cmd := sdl.AcquireGPUCommandBuffer(app.device)
-	if cmd == nil {
-		fmt.eprintfln("FPS overlay AcquireGPUCommandBuffer failed: %s", sdl.GetError())
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-		app.fps_texture = nil
-		return false
-	}
-
-	copy_pass := sdl.BeginGPUCopyPass(cmd)
-	transfer := sdl.GPUTextureTransferInfo {
-		transfer_buffer = tbuf,
-		offset          = 0,
-		pixels_per_row  = u32(atlas_w),
-		rows_per_layer  = u32(atlas_h),
-	}
-	region := sdl.GPUTextureRegion {
-		texture = app.fps_texture,
-		w       = u32(atlas_w),
-		h       = u32(atlas_h),
-		d       = 1,
-	}
-	sdl.UploadToGPUTexture(copy_pass, transfer, region, false)
-	sdl.EndGPUCopyPass(copy_pass)
-
-	fence := sdl.SubmitGPUCommandBufferAndAcquireFence(cmd)
-	if fence == nil {
-		fmt.eprintfln("FPS overlay texture upload submit failed: %s", sdl.GetError())
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-		app.fps_texture = nil
-		return false
-	}
-	defer sdl.ReleaseGPUFence(app.device, fence)
-
-	if !sdl.WaitForGPUFences(app.device, true, &fence, 1) {
-		fmt.eprintfln("FPS overlay WaitForGPUFences failed: %s", sdl.GetError())
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-		app.fps_texture = nil
-		return false
-	}
-
-	return true
-}
-
-@(private)
-fps_overlay_shutdown :: proc(app: ^App) {
-	if app.device != nil && app.fps_texture != nil {
-		sdl.ReleaseGPUTexture(app.device, app.fps_texture)
-	}
-	app.fps_texture = nil
-}
-
-@(private)
-fps_overlay_begin_frame :: proc(app: ^App) {
-	now := now_seconds()
-	if app.fps_last_time > 0 {
-		dt := now - app.fps_last_time
-		if dt > 0 {
-			instant := f32(1.0 / dt)
-			if app.fps_smooth <= 0 {
-				app.fps_smooth = instant
-			} else {
-				app.fps_smooth = app.fps_smooth * 0.9 + instant * 0.1
-			}
-			app.fps_update_accum += f32(dt)
-			if app.fps_display == 0 || app.fps_update_accum >= FPS_UPDATE_INTERVAL {
-				app.fps_display = int(app.fps_smooth + 0.5)
-				app.fps_update_accum = 0
-			}
-		}
-	}
-	app.fps_last_time = now
-}
-
-@(private)
-fps_overlay_queue :: proc(app: ^App) {
-	if !app.show_fps || app.fps_texture == nil do return
-	if app.cmd == nil || app.swapchain_texture == nil do return
-	if app.swapchain_w == 0 || app.swapchain_h == 0 do return
-
-	fps := app.fps_display
-	if fps < 0 do fps = 0
-
-	// Build "N… FPS" with the full measured rate (no artificial cap).
-	glyphs: [FPS_OVERLAY_MAX_GLYPHS]int
-	count := 0
-
-	digits: [8]int
-	dcount := 0
-	if fps == 0 {
-		digits[0] = 0
-		dcount = 1
-	} else {
-		v := fps
-		for v > 0 && dcount < len(digits) {
-			digits[dcount] = v % 10
-			dcount += 1
-			v /= 10
-		}
-		for i in 0 ..< dcount / 2 {
-			digits[i], digits[dcount - 1 - i] = digits[dcount - 1 - i], digits[i]
-		}
-	}
-
-	for i in 0 ..< dcount {
-		if count >= FPS_OVERLAY_MAX_GLYPHS do break
-		glyphs[count] = FPS_GLYPH_DIGIT_0 + digits[i]
-		count += 1
-	}
-	if count + 4 <= FPS_OVERLAY_MAX_GLYPHS {
-		glyphs[count] = FPS_GLYPH_SPACE
-		count += 1
-		glyphs[count] = FPS_GLYPH_F
-		count += 1
-		glyphs[count] = FPS_GLYPH_P
-		count += 1
-		glyphs[count] = FPS_GLYPH_S
-		count += 1
-	}
-
-	sw := f32(app.swapchain_w)
-	sh := f32(app.swapchain_h)
-	atlas_w := f32(FPS_ATLAS_COLS * FPS_CELL_W)
-	atlas_h := f32(FPS_CELL_H)
-	gw := f32(FPS_GLYPH_W * FPS_SCALE)
-	gh := f32(FPS_GLYPH_H * FPS_SCALE)
-	advance := f32(FPS_CELL_W * FPS_SCALE)
-	x := f32(FPS_MARGIN)
-	y := f32(FPS_MARGIN)
-
-	for i in 0 ..< count {
-		if len(app.draw_list) >= MAX_SPRITES do break
-
-		gi := glyphs[i]
-		u0 := f32(gi * FPS_CELL_W) / atlas_w
-		v0 := f32(0)
-		u1 := f32(gi * FPS_CELL_W + FPS_GLYPH_W) / atlas_w
-		v1 := f32(FPS_GLYPH_H) / atlas_h
-
-		x0 := x + f32(i) * advance
-		y0 := y
-		x1 := x0 + gw
-		y1 := y0 + gh
-
-		p0 := to_clip(x0, y0, sw, sh)
-		p1 := to_clip(x1, y0, sw, sh)
-		p2 := to_clip(x1, y1, sw, sh)
-		p3 := to_clip(x0, y1, sw, sh)
-
-		verts := [SPRITE_VERT_COUNT]Vertex {
-			{pos = p0, uv = {u0, v0}},
-			{pos = p1, uv = {u1, v0}},
-			{pos = p2, uv = {u1, v1}},
-			{pos = p0, uv = {u0, v0}},
-			{pos = p2, uv = {u1, v1}},
-			{pos = p3, uv = {u0, v1}},
-		}
-		append(&app.draw_list, Queued_Sprite{texture = app.fps_texture, verts = verts})
-	}
-}

engine/shader_backend_test.odin

@@ -27,6 +27,15 @@ choose_shader_runtime_prefers_msl :: proc(t: ^testing.T) {
 	testing.expect_value(t, rt.format, sdl.GPUShaderFormat{.MSL})
 }
 
+@(test)
+choose_shader_runtime_prefers_dxil_without_msl :: proc(t: ^testing.T) {
+	rt, ok := choose_shader_runtime_from_formats({.DXIL, .SPIRV})
+	testing.expect(t, ok, "should pick a runtime when DXIL is available")
+	testing.expect_value(t, rt.backend, Shader_Backend.DSD12_DXIL)
+	testing.expect_value(t, rt.shader_dir, "shaders/d3d12")
+	testing.expect_value(t, rt.format, sdl.GPUShaderFormat{.DXIL})
+}
+
 @(test)
 choose_shader_runtime_spirv_only :: proc(t: ^testing.T) {
 	rt, ok := choose_shader_runtime_from_formats({.SPIRV})

engine/sprite.odin

@@ -5,12 +5,14 @@ import sdl "vendor:sdl3"
 Vec2 :: [2]f32
 
 Sprite :: struct {
-	data:     ^Character_Data,
-	position: Vec2,
-	clip:     string,
-	frame:    int,
-	time:     f32,
-	flip_x:   bool,
+	data:      ^Character_Data,
+	position:  Vec2,
+	clip:      string,
+	clip_def:  Clip_Def,
+	has_clip:  bool,
+	frame:     int,
+	time:      f32,
+	flip_x:    bool,
 }
 
 spawn_sprite :: proc(
@@ -24,16 +26,14 @@ spawn_sprite :: proc(
 		position = position,
 	}
 	set_sprite_clip(&sprite, clip)
-	if frame != 0 {
-		c, ok := character_clip(sprite.data, sprite.clip)
-		if ok {
-			if frame < 0 {
-				sprite.frame = 0
-			} else if frame >= len(c.frames) {
-				sprite.frame = len(c.frames) - 1
-			} else {
-				sprite.frame = frame
-			}
+	if frame != 0 && sprite.has_clip {
+		c := sprite.clip_def
+		if frame < 0 {
+			sprite.frame = 0
+		} else if frame >= len(c.frames) {
+			sprite.frame = len(c.frames) - 1
+		} else {
+			sprite.frame = frame
 		}
 	}
 	return sprite
@@ -42,9 +42,9 @@ spawn_sprite :: proc(
 update_sprite :: proc(sprite: ^Sprite, dt: f32) {
 	if sprite == nil || sprite.data == nil do return
 	if dt <= 0 do return
+	if !sprite.has_clip do return
 
-	clip, ok := character_clip(sprite.data, sprite.clip)
-	if !ok do return
+	clip := sprite.clip_def
 
 	frame_count := len(clip.frames)
 	if frame_count <= 0 do return
@@ -82,26 +82,46 @@ to_clip :: proc(px, py, sw, sh: f32) -> [2]f32 {
 	}
 }
 
+// Axis-aligned quad: two unique x and y values, so scale once and reuse.
+sprite_quad_to_clip :: proc(x0, y0, x1, y1, sw, sh: f32) -> [4]Vec2 {
+	sx := 2.0 / sw
+	sy := 2.0 / sh
+
+	left := x0 * sx - 1
+	right := x1 * sx - 1
+	top := 1 - y0 * sy
+	bottom := 1 - y1 * sy
+
+	return {
+		{left, top},
+		{right, top},
+		{right, bottom},
+		{left, bottom},
+	}
+}
+
 draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
+	draw_sprite_batched(app, sprite, 0)
+}
+
+// Nonzero batch_group lets end_frame regroup consecutive same-group sprites by
+// texture. Group 0 keeps exact submission order for correct alpha overlap.
+draw_sprite_batched :: proc(app: ^App, sprite: ^Sprite, batch_group: u32) {
 	if app.cmd == nil || app.swapchain_texture == nil {
 		return
 	}
 	if sprite == nil || sprite.data == nil || sprite.data.texture == nil {
 		return
 	}
-	// Reserve room for the engine FPS overlay glyphs when enabled.
-	max_game := MAX_SPRITES
-	if app.show_fps && app.fps_texture != nil {
-		max_game -= FPS_OVERLAY_MAX_GLYPHS
+	if len(app.draw_list) >= MAX_SPRITES {
+		return
 	}
-	if len(app.draw_list) >= max_game {
+	if !sprite.has_clip do return
+	if sprite.frame < 0 || sprite.frame >= len(sprite.clip_def.frames) {
 		return
 	}
 
-	frame, ok := character_frame(sprite.data, sprite.clip, sprite.frame)
-	if !ok {
-		return
-	}
+	frame := sprite.clip_def.frames[sprite.frame]
 
 	src_w := f32(frame.source_size[0])
 	src_h := f32(frame.source_size[1])
@@ -129,10 +149,8 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 
 	sw := f32(app.swapchain_w)
 	sh := f32(app.swapchain_h)
-	p0 := to_clip(x0_px, y0_px, sw, sh)
-	p1 := to_clip(x1_px, y0_px, sw, sh)
-	p2 := to_clip(x1_px, y1_px, sw, sh)
-	p3 := to_clip(x0_px, y1_px, sw, sh)
+	points := sprite_quad_to_clip(x0_px, y0_px, x1_px, y1_px, sw, sh)
+	p0, p1, p2, p3 := points[0], points[1], points[2], points[3]
 
 	tex_w := f32(sprite.data.width)
 	tex_h := f32(sprite.data.height)
@@ -147,18 +165,38 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 		{pos = p3, uv = {u0, v1}},
 	}
 
-	append(&app.draw_list, Queued_Sprite{texture = sprite.data.texture, verts = verts})
+	append(
+		&app.draw_list,
+		Queued_Sprite {
+			texture = sprite.data.texture,
+			verts = verts,
+			batch_group = batch_group,
+		},
+	)
 }
 
 set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {
 	if sprite == nil || sprite.data == nil do return
 
-	if sprite.clip == clip do return
+	if sprite.clip == clip && sprite.has_clip do return
 
-	_, ok := character_clip(sprite.data, clip)
+	def, ok := character_clip(sprite.data, clip)
 	if !ok do return
 
+	set_sprite_clip_def(sprite, clip, def)
+}
+
+// Applies a pre-resolved clip without looking up the character clip map.
+// Use when callers already hold Clip_Def (e.g. thrashing between known clips).
+set_sprite_clip_def :: proc(sprite: ^Sprite, clip: string, def: Clip_Def) {
+	if sprite == nil do return
+	if len(def.frames) == 0 do return
+
+	if sprite.clip == clip && sprite.has_clip do return
+
 	sprite.clip = clip
+	sprite.clip_def = def
+	sprite.has_clip = true
 	sprite.frame = 0
 	sprite.time = 0
 }

examples/clip_thrash/main.odin

@@ -0,0 +1,80 @@
+package main
+
+import "core:fmt"
+import eng "pkg:engine"
+
+// Clip thrash: flip every sprite between idle/walk each frame via set_sprite_clip_def.
+COUNT :: eng.MAX_SPRITES
+COLS :: 16
+FRAME_LOG_EVERY :: 60
+
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "clip_thrash", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	idle_def, idle_ok := eng.character_clip(&data, "idle")
+	walk_def, walk_ok := eng.character_clip(&data, "walk")
+	if !idle_ok || !walk_ok do return
+
+	sprites: [COUNT]eng.Sprite
+	for i in 0 ..< COUNT {
+		col := i % COLS
+		row := i / COLS
+		pos := eng.Vec2 {
+			f32(40 + col * 48),
+			f32(80 + row * 60),
+		}
+		sprites[i] = eng.spawn_sprite(&data, pos, "idle", i % 5)
+	}
+
+	app.camera.position = {400, 400}
+
+	last := eng.now_seconds()
+	frame_i := 0
+	sum_ms: f64
+	peak_ms: f64
+	use_walk := false
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+		frame_ms := f64(dt) * 1000.0
+		sum_ms += frame_ms
+		if frame_ms > peak_ms do peak_ms = frame_ms
+		frame_i += 1
+
+		if frame_i % FRAME_LOG_EVERY == 0 {
+			avg := sum_ms / f64(FRAME_LOG_EVERY)
+			fps := 1000.0 / avg if avg > 0 else 0
+			fmt.printfln(
+				"clip_thrash frame: avg=%.2f ms (%.1f FPS) peak=%.2f ms over %d frames",
+				avg,
+				fps,
+				peak_ms,
+				FRAME_LOG_EVERY,
+			)
+			sum_ms = 0
+			peak_ms = 0
+		}
+
+		clip := "walk" if use_walk else "idle"
+		def := walk_def if use_walk else idle_def
+		use_walk = !use_walk
+		for &s in sprites {
+			eng.set_sprite_clip_def(&s, clip, def)
+			eng.update_sprite(&s, dt)
+		}
+
+		eng.begin_frame(&app)
+		for &s in sprites {
+			eng.draw_sprite(&app, &s)
+		}
+		eng.end_frame(&app)
+	}
+}

examples/crowd/main.odin

@@ -1,14 +1,12 @@
 package main
 
+import "core:fmt"
 import eng "pkg:engine"
 
 // Many sprites sharing one Character_Data (Flyweight) — good batching demo.
-COUNT :: 1000
-COLS :: 40
-CELL_W :: 20
-CELL_H :: 24
-ORIGIN_X :: 20
-ORIGIN_Y :: 40
+COUNT :: eng.MAX_SPRITES
+COLS :: 16
+FRAME_LOG_EVERY :: 60
 
 main :: proc() {
 	app: eng.App
@@ -24,26 +22,42 @@ main :: proc() {
 		col := i % COLS
 		row := i / COLS
 		pos := eng.Vec2 {
-			f32(ORIGIN_X + col * CELL_W),
-			f32(ORIGIN_Y + row * CELL_H),
+			f32(40 + col * 48),
+			f32(80 + row * 60),
 		}
 		clip := "idle" if (i % 2) == 0 else "walk"
 		sprites[i] = eng.spawn_sprite(&data, pos, clip, i % 5)
 	}
 
-	// Look at the middle of the grid
-	rows := (COUNT + COLS - 1) / COLS
-	app.camera.position = {
-		f32(ORIGIN_X + (COLS - 1) * CELL_W / 2),
-		f32(ORIGIN_Y + (rows - 1) * CELL_H / 2),
-	}
+	app.camera.position = {400, 400}
 
 	last := eng.now_seconds()
+	frame_i := 0
+	sum_ms: f64
+	peak_ms: f64
 
 	for eng.events() {
 		now := eng.now_seconds()
 		dt := f32(now - last)
 		last = now
+		frame_ms := f64(dt) * 1000.0
+		sum_ms += frame_ms
+		if frame_ms > peak_ms do peak_ms = frame_ms
+		frame_i += 1
+
+		if frame_i % FRAME_LOG_EVERY == 0 {
+			avg := sum_ms / f64(FRAME_LOG_EVERY)
+			fps := 1000.0 / avg if avg > 0 else 0
+			fmt.printfln(
+				"crowd frame: avg=%.2f ms (%.1f FPS) peak=%.2f ms over %d frames",
+				avg,
+				fps,
+				peak_ms,
+				FRAME_LOG_EVERY,
+			)
+			sum_ms = 0
+			peak_ms = 0
+		}
 
 		for &s in sprites {
 			eng.update_sprite(&s, dt)

examples/crowd_batch/main.odin

@@ -0,0 +1,79 @@
+package main
+
+import "core:fmt"
+import eng "pkg:engine"
+
+// Multi-texture batching stress: two Character_Data (two GPU textures), alternating sprites.
+COUNT :: eng.MAX_SPRITES
+COLS :: 16
+FRAME_LOG_EVERY :: 60
+BATCH_GROUP :: u32(1)
+TOAD_JSON :: "assets_baked/characters/toad/toad.char.json"
+
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "crowd_batch", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data_a, ok_a := eng.load_character_data(&app, TOAD_JSON)
+	if !ok_a do return
+	defer eng.destroy_character_data(&app, &data_a)
+
+	data_b, ok_b := eng.load_character_data(&app, TOAD_JSON)
+	if !ok_b do return
+	defer eng.destroy_character_data(&app, &data_b)
+
+	sprites: [COUNT]eng.Sprite
+	for i in 0 ..< COUNT {
+		col := i % COLS
+		row := i / COLS
+		pos := eng.Vec2 {
+			f32(40 + col * 48),
+			f32(80 + row * 60),
+		}
+		clip := "idle" if (i % 2) == 0 else "walk"
+		data := &data_a if (i % 2) == 0 else &data_b
+		sprites[i] = eng.spawn_sprite(data, pos, clip, i % 5)
+	}
+
+	app.camera.position = {400, 400}
+
+	last := eng.now_seconds()
+	frame_i := 0
+	sum_ms: f64
+	peak_ms: f64
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+		frame_ms := f64(dt) * 1000.0
+		sum_ms += frame_ms
+		if frame_ms > peak_ms do peak_ms = frame_ms
+		frame_i += 1
+
+		if frame_i % FRAME_LOG_EVERY == 0 {
+			avg := sum_ms / f64(FRAME_LOG_EVERY)
+			fps := 1000.0 / avg if avg > 0 else 0
+			fmt.printfln(
+				"crowd_batch frame: avg=%.2f ms (%.1f FPS) peak=%.2f ms over %d frames",
+				avg,
+				fps,
+				peak_ms,
+				FRAME_LOG_EVERY,
+			)
+			sum_ms = 0
+			peak_ms = 0
+		}
+
+		for &s in sprites {
+			eng.update_sprite(&s, dt)
+		}
+
+		eng.begin_frame(&app)
+		for &s in sprites {
+			eng.draw_sprite_batched(&app, &s, BATCH_GROUP)
+		}
+		eng.end_frame(&app)
+	}
+}

examples/crowd_overdraw/main.odin

@@ -0,0 +1,70 @@
+package main
+
+import "core:fmt"
+import eng "pkg:engine"
+
+// GPU overdraw stress: MAX_SPRITES stacked near one world point.
+COUNT :: eng.MAX_SPRITES
+FRAME_LOG_EVERY :: 60
+
+main :: proc() {
+	app: eng.App
+	if !eng.init(&app, "crowd_overdraw", 800, 600) do return
+	defer eng.shutdown(&app)
+
+	data, ok := eng.load_character_data(&app, "assets_baked/characters/toad/toad.char.json")
+	if !ok do return
+	defer eng.destroy_character_data(&app, &data)
+
+	center := eng.Vec2{400, 400}
+	sprites: [COUNT]eng.Sprite
+	for i in 0 ..< COUNT {
+		jitter := eng.Vec2 {
+			f32((i % 7) - 3),
+			f32((i % 5) - 2),
+		}
+		clip := "idle" if (i % 2) == 0 else "walk"
+		sprites[i] = eng.spawn_sprite(&data, center + jitter, clip, i % 5)
+	}
+
+	app.camera.position = {400, 400}
+
+	last := eng.now_seconds()
+	frame_i := 0
+	sum_ms: f64
+	peak_ms: f64
+
+	for eng.events() {
+		now := eng.now_seconds()
+		dt := f32(now - last)
+		last = now
+		frame_ms := f64(dt) * 1000.0
+		sum_ms += frame_ms
+		if frame_ms > peak_ms do peak_ms = frame_ms
+		frame_i += 1
+
+		if frame_i % FRAME_LOG_EVERY == 0 {
+			avg := sum_ms / f64(FRAME_LOG_EVERY)
+			fps := 1000.0 / avg if avg > 0 else 0
+			fmt.printfln(
+				"crowd_overdraw frame: avg=%.2f ms (%.1f FPS) peak=%.2f ms over %d frames",
+				avg,
+				fps,
+				peak_ms,
+				FRAME_LOG_EVERY,
+			)
+			sum_ms = 0
+			peak_ms = 0
+		}
+
+		for &s in sprites {
+			eng.update_sprite(&s, dt)
+		}
+
+		eng.begin_frame(&app)
+		for &s in sprites {
+			eng.draw_sprite(&app, &s)
+		}
+		eng.end_frame(&app)
+	}
+}