camera

Batch adjacent same-texture sprite draws in end_frame.
Replaces per-sprite DrawGPUPrimitives with texture runs so shared atlases issue one GPU draw.

engine/app.odin

@@ -35,6 +35,7 @@ App :: struct {
 	transfer_buffer:   ^sdl.GPUTransferBuffer,
 	draw_list:         [dynamic]Queued_Sprite,
 	clear_color:       sdl.FColor,
+	camera:            Camera,
 }
 
 Shader_Backend :: enum {
@@ -124,6 +125,8 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 
 	app.draw_list = make([dynamic]Queued_Sprite)
 
+	app.camera = camera_default()
+
 	return true
 }
 
@@ -270,9 +273,13 @@ end_frame :: proc(app: ^App) {
 	app.render_pass = sdl.BeginGPURenderPass(cmd, &color_info, 1, nil)
 	sdl.BindGPUGraphicsPipeline(app.render_pass, app.pipeline)
 
-	for q, i in app.draw_list {
+	i := 0
+	for i < n {
+		run := texture_run_len(app.draw_list[:], i)
+		q0 := app.draw_list[i]
+
 		sampler_binding := sdl.GPUTextureSamplerBinding {
-			texture = q.texture,
+			texture = q0.texture,
 			sampler = app.sampler,
 		}
 		sdl.BindGPUFragmentSamplers(app.render_pass, 0, &sampler_binding, 1)
@@ -282,9 +289,11 @@ end_frame :: proc(app: ^App) {
 			offset = u32(i * SPRITE_VERTS_SIZE),
 		}
 		sdl.BindGPUVertexBuffers(app.render_pass, 0, &vb_binding, 1)
-		sdl.DrawGPUPrimitives(app.render_pass, SPRITE_VERT_COUNT, 1, 0, 0)
-	}
 
+		sdl.DrawGPUPrimitives(app.render_pass, u32(run * SPRITE_VERT_COUNT), 1, 0, 0)
+
+		i += run
+	}
 	sdl.EndGPURenderPass(app.render_pass)
 	app.render_pass = nil
 
@@ -418,3 +427,17 @@ create_sprite_pipeline :: proc(app: ^App) -> ^sdl.GPUGraphicsPipeline {
 
 	return pipeline
 }
+
+texture_run_len :: proc(list: []Queued_Sprite, start: int) -> int {
+	if start < 0 || start >= len(list) do return 0
+
+	tex := list[start].texture
+	n := 1
+
+	for i in start + 1 ..< len(list) {
+		if list[i].texture != tex do break
+		n += 1
+	}
+
+	return n
+}

engine/camera.odin

@@ -0,0 +1,17 @@
+package engine
+
+Camera :: struct {
+	position: Vec2,
+	anchor:   Vec2,
+}
+
+camera_default :: proc() -> Camera {
+	return Camera{position = {0, 0}, anchor = {0.5, 0.5}}
+}
+
+world_to_screen :: proc(cam: Camera, world: Vec2, viewport: Vec2) -> Vec2 {
+	return {
+		world.x - cam.position.x + viewport.x * cam.anchor[0],
+		world.y - cam.position.y + viewport.y * cam.anchor[1],
+	}
+}

engine/sprite.odin

@@ -109,14 +109,17 @@ draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
 	trim_y := f32(frame.trim_offset[1])
 	pivot := sprite.data.def.pivot
 
-	canvas_top := sprite.position.y - src_h * pivot[1]
+	viewport := Vec2{f32(app.swapchain_w), f32(app.swapchain_h)}
+	feet := world_to_screen(app.camera, sprite.position, viewport)
+
+	canvas_top := feet.y - src_h * pivot[1]
 	x0_px, y0_px: f32
 	if sprite.flip_x {
-		canvas_left := sprite.position.x - (1.0 - pivot[0]) * src_w
+		canvas_left := feet.x - (1.0 - pivot[0]) * src_w
 		x0_px = canvas_left + (src_w - trim_x - fw)
 		y0_px = canvas_top + trim_y
 	} else {
-		canvas_left := sprite.position.x - src_w * pivot[0]
+		canvas_left := feet.x - src_w * pivot[0]
 		x0_px = canvas_left + trim_x
 		y0_px = canvas_top + trim_y
 	}
@@ -147,10 +150,7 @@ 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})
 }
 
 set_sprite_clip :: proc(sprite: ^Sprite, clip: string) {

examples/toad/main.odin

@@ -39,6 +39,8 @@ main :: proc() {
 		} else {
 			eng.set_sprite_clip(&toad, "idle")
 		}
+
+		app.camera.position = toad.position - {0, 100}
 		eng.update_sprite(&toad, dt)
 
 		eng.begin_frame(&app)