Add crowd_batch, crowd_overdraw, and clip_thrash stress examples

Test sprite clip_def cache on set_sprite_clip

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

@@ -16,8 +16,15 @@ 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 {
@@ -65,7 +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
@@ -76,6 +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) {
@@ -242,7 +253,11 @@ end_frame :: proc(app: ^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())
@@ -286,26 +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
@@ -454,3 +463,60 @@ 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 insertion sort is sufficient while MAX_SPRITES is 128.
+		for i in start + 1 ..< end {
+			item := list[i]
+			j := i
+			for j > start {
+				if uintptr(list[j - 1].texture) <= uintptr(item.texture) {
+					break
+				}
+				list[j] = list[j - 1]
+				j -= 1
+			}
+			list[j] = item
+		}
+		start = end
+	}
+}

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 +74,293 @@ 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_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_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/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
@@ -82,7 +82,31 @@ 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
 	}
@@ -92,12 +116,13 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 	if len(app.draw_list) >= MAX_SPRITES {
 		return
 	}
-
-	frame, ok := character_frame(sprite.data, sprite.clip, sprite.frame)
-	if !ok {
+	if !sprite.has_clip do return
+	if sprite.frame < 0 || sprite.frame >= len(sprite.clip_def.frames) {
 		return
 	}
 
+	frame := sprite.clip_def.frames[sprite.frame]
+
 	src_w := f32(frame.source_size[0])
 	src_h := f32(frame.source_size[1])
 	if src_w <= 0 do src_w = f32(frame.rect[2])
@@ -124,10 +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)
@@ -142,18 +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

@@ -1,9 +1,12 @@
 package main
 
+import "core:fmt"
 import eng "pkg:engine"
 
 // Many sprites sharing one Character_Data (Flyweight) — good batching demo.
-COUNT :: 24
+COUNT :: eng.MAX_SPRITES
+COLS :: 16
+FRAME_LOG_EVERY :: 60
 
 main :: proc() {
 	app: eng.App
@@ -16,25 +19,45 @@ main :: proc() {
 
 	sprites: [COUNT]eng.Sprite
 	for i in 0 ..< COUNT {
-		col := i % 8
-		row := i / 8
+		col := i % COLS
+		row := i / COLS
 		pos := eng.Vec2 {
-			f32(120 + col * 80),
-			f32(280 + row * 120),
+			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
 	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)
+	}
+}