Initial pipeline work

Migrates the toad example from SDL’s 2D Renderer API to SDL_GPU, keeping the same Character_Data / Sprite engine API and baked asset pipeline.

- Replaces CreateWindowAndRenderer / RenderTexture with GPU device + swapchain framing (begin_frame / end_frame)
- Adds sprite vertex/fragment GLSL shaders and compiled SPIR-V (shaders/sprite.*.glsl / .spv)
- Uploads atlas PNGs as GPUTexture via transfer buffer + copy pass (with fence sync)
- Draws sprites as UV quads (DrawGPUPrimitives) using atlas frame rects from char.json

engine/app.odin

@@ -3,9 +3,29 @@ package engine
 import "core:fmt"
 import sdl "vendor:sdl3"
 
+Vertex :: struct {
+	pos: [2]f32, // clip space, -1..1
+	uv:  [2]f32, // 0..1 atlas coords (used later in draw_sprite)
+}
+
+SPRITE_VERT_COUNT :: 6
+VERTEX_BUFFER_SIZE :: SPRITE_VERT_COUNT * size_of(Vertex)
+
+VERT_SPV := #load("../shaders/sprite.vert.spv")
+FRAG_SPV := #load("../shaders/sprite.frag.spv")
+
 App :: struct {
-	window:   ^sdl.Window,
-	renderer: ^sdl.Renderer,
+	window:            ^sdl.Window,
+	device:            ^sdl.GPUDevice,
+	pipeline:          ^sdl.GPUGraphicsPipeline,
+	sampler:           ^sdl.GPUSampler,
+	cmd:               ^sdl.GPUCommandBuffer,
+	render_pass:       ^sdl.GPURenderPass,
+	swapchain_texture: ^sdl.GPUTexture,
+	swapchain_w:       u32,
+	swapchain_h:       u32,
+	vertex_buffer:     ^sdl.GPUBuffer,
+	transfer_buffer:   ^sdl.GPUTransferBuffer,
 }
 
 init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
@@ -14,8 +34,64 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 		return false
 	}
 
-	if !sdl.CreateWindowAndRenderer(title, width, height, {}, &app.window, &app.renderer) {
-		fmt.eprintfln("CreateWindowAndRenderer failed: %s", sdl.GetError())
+	app.window = sdl.CreateWindow(title, width, height, {})
+
+	if app.window == nil {
+		fmt.eprintfln("CreateWindow failed: %s", sdl.GetError())
+		return false
+	}
+
+	app.device = sdl.CreateGPUDevice({.SPIRV}, true, nil)
+	if app.device == nil {
+		fmt.eprintfln("CreateGPUDevice failed: %s", sdl.GetError())
+		return false
+	}
+
+	if !sdl.ClaimWindowForGPUDevice(app.device, app.window) {
+		fmt.eprintfln("ClaimWindowForGPUDevice failed: %s", sdl.GetError())
+		return false
+	}
+
+	app.pipeline = create_sprite_pipeline(app.device, app.window)
+	if app.pipeline == nil {
+		fmt.eprintfln("create_sprite_pipeline failed: %s", sdl.GetError())
+		return false
+	}
+
+	app.sampler = sdl.CreateGPUSampler(
+		app.device,
+		{
+			min_filter = .NEAREST,
+			mag_filter = .NEAREST,
+			mipmap_mode = .NEAREST,
+			address_mode_u = .CLAMP_TO_EDGE,
+			address_mode_v = .CLAMP_TO_EDGE,
+			address_mode_w = .CLAMP_TO_EDGE,
+		},
+	)
+
+	if app.sampler == nil {
+		fmt.eprintfln("CreateGPUSampler failed: %s", sdl.GetError())
+		return false
+	}
+
+	app.vertex_buffer = sdl.CreateGPUBuffer(
+		app.device,
+		{usage = {.VERTEX}, size = VERTEX_BUFFER_SIZE},
+	)
+
+	if app.vertex_buffer == nil {
+		fmt.eprintfln("CreateGPUBuffer failed: %s", sdl.GetError())
+		return false
+	}
+
+	app.transfer_buffer = sdl.CreateGPUTransferBuffer(
+		app.device,
+		{usage = .UPLOAD, size = VERTEX_BUFFER_SIZE},
+	)
+
+	if app.transfer_buffer == nil {
+		fmt.eprintfln("CreateGPUTransferBuffer failed: %s", sdl.GetError())
 		return false
 	}
 
@@ -23,14 +99,43 @@ init :: proc(app: ^App, title: cstring, width, height: i32) -> bool {
 }
 
 shutdown :: proc(app: ^App) {
-	if app.renderer != nil do sdl.DestroyRenderer(app.renderer)
-	if app.window != nil do sdl.DestroyWindow(app.window)
+	if app.device != nil {
+		ok := sdl.WaitForGPUIdle(app.device)
+		if !ok {
+			fmt.eprintfln("WaitForGPUIdle failed")
+		}
+
+		if app.transfer_buffer != nil {
+			sdl.ReleaseGPUTransferBuffer(app.device, app.transfer_buffer)
+		}
+
+		if app.vertex_buffer != nil {
+			sdl.ReleaseGPUBuffer(app.device, app.vertex_buffer)
+		}
+
+		if app.sampler != nil {
+			sdl.ReleaseGPUSampler(app.device, app.sampler)
+		}
+
+		if app.pipeline != nil {
+			sdl.ReleaseGPUGraphicsPipeline(app.device, app.pipeline)
+		}
+
+		if app.window != nil {
+			sdl.ReleaseWindowFromGPUDevice(app.device, app.window)
+		}
+		sdl.DestroyGPUDevice(app.device)
+	}
+
+	if app.window != nil {
+		sdl.DestroyWindow(app.window)
+	}
 
 	sdl.Quit()
 	app^ = {}
 }
 
-pump_events :: proc() -> bool {
+events :: proc() -> bool {
 	event: sdl.Event
 
 	for sdl.PollEvent(&event) {
@@ -42,15 +147,137 @@ pump_events :: proc() -> bool {
 	return true
 }
 
-begin_frame :: proc(app: ^App, r: u8 = 30, g: u8 = 30, b: u8 = 40, a: u8 = 255) {
-	sdl.SetRenderDrawColor(app.renderer, r, g, b, a)
-	sdl.RenderClear(app.renderer)
+begin_frame :: proc(app: ^App, clear: sdl.FColor = {0.12, 0.12, 0.16, 1}) {
+	app.cmd = sdl.AcquireGPUCommandBuffer(app.device)
+
+	if app.cmd == nil {
+		fmt.eprintfln("AcquireGPUCommandBuffer failed: %s", sdl.GetError())
+		return
+	}
+
+	ok := sdl.WaitAndAcquireGPUSwapchainTexture(
+		app.cmd,
+		app.window,
+		&app.swapchain_texture,
+		&app.swapchain_w,
+		&app.swapchain_h,
+	)
+
+	if !ok || app.swapchain_texture == nil {
+		return
+	}
+
+	color_info := sdl.GPUColorTargetInfo {
+		texture     = app.swapchain_texture,
+		clear_color = clear,
+		load_op     = .CLEAR,
+		store_op    = .STORE,
+	}
+
+	app.render_pass = sdl.BeginGPURenderPass(app.cmd, &color_info, 1, nil)
+
+	sdl.BindGPUGraphicsPipeline(app.render_pass, app.pipeline)
 }
 
 end_frame :: proc(app: ^App) {
-	sdl.RenderPresent(app.renderer)
+	if app.render_pass != nil {
+		sdl.EndGPURenderPass(app.render_pass)
+		app.render_pass = nil
+	}
+
+	if app.cmd != nil {
+		ok := sdl.SubmitGPUCommandBuffer(app.cmd)
+		if !ok {
+			fmt.eprintfln("SubmitGPUCommandBuffer failed")
+		}
+		app.cmd = nil
+	}
+
+	app.swapchain_texture = nil
 }
 
-renderer :: proc(app: ^App) -> ^sdl.Renderer {
-	return app.renderer
+load_spirv_shader :: proc(
+	device: ^sdl.GPUDevice,
+	code: []u8,
+	stage: sdl.GPUShaderStage,
+	num_samplers: u32,
+) -> ^sdl.GPUShader {
+	return sdl.CreateGPUShader(
+		device,
+		{
+			code_size = len(code),
+			code = raw_data(code),
+			entrypoint = "main",
+			format = {.SPIRV},
+			stage = stage,
+			num_samplers = num_samplers,
+			num_storage_textures = 0,
+			num_storage_buffers = 0,
+			num_uniform_buffers = 0,
+		},
+	)
+}
+
+create_sprite_pipeline :: proc(
+	device: ^sdl.GPUDevice,
+	window: ^sdl.Window,
+) -> ^sdl.GPUGraphicsPipeline {
+	vert := load_spirv_shader(device, VERT_SPV[:], .VERTEX, 0)
+	if vert == nil do return nil
+
+	frag := load_spirv_shader(device, FRAG_SPV[:], .FRAGMENT, 1)
+	if frag == nil {
+		sdl.ReleaseGPUShader(device, vert)
+		return nil
+	}
+
+	swap_format := sdl.GetGPUSwapchainTextureFormat(device, window)
+
+
+	blend := sdl.GPUColorTargetBlendState {
+		src_color_blendfactor = .SRC_ALPHA,
+		dst_color_blendfactor = .ONE_MINUS_SRC_ALPHA,
+		color_blend_op        = .ADD,
+		src_alpha_blendfactor = .ONE,
+		dst_alpha_blendfactor = .ONE_MINUS_SRC_ALPHA,
+		alpha_blend_op        = .ADD,
+		enable_blend          = true,
+	}
+
+	color_target := sdl.GPUColorTargetDescription {
+		format      = swap_format,
+		blend_state = blend,
+	}
+
+	vb_desc := sdl.GPUVertexBufferDescription {
+		slot       = 0,
+		pitch      = u32(size_of(Vertex)),
+		input_rate = .VERTEX,
+	}
+
+	attrs := [2]sdl.GPUVertexAttribute {
+		{location = 0, buffer_slot = 0, format = .FLOAT2, offset = 0},
+		{location = 1, buffer_slot = 0, format = .FLOAT2, offset = u32(offset_of(Vertex, uv))},
+	}
+
+	pipeline_info := sdl.GPUGraphicsPipelineCreateInfo {
+		vertex_shader = vert,
+		fragment_shader = frag,
+		vertex_input_state = {
+			vertex_buffer_descriptions = &vb_desc,
+			num_vertex_buffers = 1,
+			vertex_attributes = raw_data(attrs[:]),
+			num_vertex_attributes = 2,
+		},
+		primitive_type = .TRIANGLELIST,
+		rasterizer_state = {fill_mode = .FILL},
+		target_info = {color_target_descriptions = &color_target, num_color_targets = 1},
+	}
+
+	pipeline := sdl.CreateGPUGraphicsPipeline(device, pipeline_info)
+
+	sdl.ReleaseGPUShader(device, vert)
+	sdl.ReleaseGPUShader(device, frag)
+
+	return pipeline
 }

engine/character_data.odin

@@ -2,6 +2,7 @@ package engine
 
 import "core:encoding/json"
 import "core:fmt"
+import "core:mem"
 import "core:os"
 import "core:path/filepath"
 import "core:strings"
@@ -30,16 +31,12 @@ Char_Def :: struct {
 
 Character_Data :: struct {
 	def:     Char_Def,
-	texture: ^sdl.Texture,
+	texture: ^sdl.GPUTexture,
+	width:   int,
+	height:  int,
 }
 
-load_character_data :: proc(
-	renderer: ^sdl.Renderer,
-	character_json_path: string,
-) -> (
-	Character_Data,
-	bool,
-) {
+load_character_data :: proc(app: ^App, character_json_path: string) -> (Character_Data, bool) {
 	file_data, read_err := os.read_entire_file(character_json_path, context.allocator)
 	if read_err != nil {
 		fmt.eprintfln("failed to read %s: %v", character_json_path, read_err)
@@ -75,18 +72,120 @@ load_character_data :: proc(
 	}
 	defer sdl.DestroySurface(surface)
 
-	out.texture = sdl.CreateTextureFromSurface(renderer, surface)
+	rgba_surface := surface
+	converted_surface: ^sdl.Surface
+	defer {
+		if converted_surface != nil do sdl.DestroySurface(converted_surface)
+	}
+	if surface.format != .ABGR8888 {
+		converted_surface = sdl.ConvertSurface(surface, .ABGR8888)
+		if converted_surface == nil {
+			fmt.eprintfln("ConvertSurface(ABGR8888) failed: %s", sdl.GetError())
+			return {}, false
+		}
+		rgba_surface = converted_surface
+	}
+
+	out.width = int(rgba_surface.w)
+	out.height = int(rgba_surface.h)
+
+	out.texture = sdl.CreateGPUTexture(
+		app.device,
+		{
+			type = .D2,
+			format = .R8G8B8A8_UNORM,
+			usage = {.SAMPLER},
+			width = u32(out.width),
+			height = u32(out.height),
+			layer_count_or_depth = 1,
+			num_levels = 1,
+			sample_count = ._1,
+		},
+	)
+
 	if out.texture == nil {
-		fmt.eprintfln("CreateTextureFromSurface failed: %s", sdl.GetError())
+		fmt.eprintfln("CreateGPUTexture failed: %s", sdl.GetError())
 		return {}, false
 	}
-	sdl.SetTextureScaleMode(out.texture, .NEAREST)
+
+	upload_size := int(rgba_surface.pitch) * int(rgba_surface.h)
+	tbuf := sdl.CreateGPUTransferBuffer(app.device, {usage = .UPLOAD, size = u32(upload_size)})
+
+	if tbuf == nil {
+		fmt.eprintfln("CreateGPUTransferBuffer failed: %s", sdl.GetError())
+		sdl.ReleaseGPUTexture(app.device, out.texture)
+		return {}, false
+	}
+
+	map_ptr := sdl.MapGPUTransferBuffer(app.device, tbuf, false)
+
+	if map_ptr == nil {
+		fmt.eprintfln("MapGPUTransferBuffer failed: %s", sdl.GetError())
+		sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
+		sdl.ReleaseGPUTexture(app.device, out.texture)
+		return {}, false
+	}
+
+	mem.copy(map_ptr, rgba_surface.pixels, upload_size)
+	sdl.UnmapGPUTransferBuffer(app.device, tbuf)
+
+	cmd := sdl.AcquireGPUCommandBuffer(app.device)
+	if cmd == nil {
+		fmt.eprintfln("AcquireGPUCommandBuffer failed: %s", sdl.GetError())
+		sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
+		sdl.ReleaseGPUTexture(app.device, out.texture)
+		return {}, false
+	}
+
+	copy_pass := sdl.BeginGPUCopyPass(cmd)
+
+	transfer := sdl.GPUTextureTransferInfo {
+		transfer_buffer = tbuf,
+		offset          = 0,
+		pixels_per_row  = u32(rgba_surface.pitch / 4), // RGBA8888 => 4 bytes/pixel
+		rows_per_layer  = u32(rgba_surface.h),
+	}
+	region := sdl.GPUTextureRegion {
+		texture   = out.texture,
+		mip_level = 0,
+		layer     = 0,
+		x         = 0,
+		y         = 0,
+		z         = 0,
+		w         = u32(rgba_surface.w),
+		h         = u32(rgba_surface.h),
+		d         = 1,
+	}
+	sdl.UploadToGPUTexture(copy_pass, transfer, region, false)
+	sdl.EndGPUCopyPass(copy_pass)
+	fence := sdl.SubmitGPUCommandBufferAndAcquireFence(cmd)
+	if fence == nil {
+		fmt.eprintfln("SubmitGPUCommandBufferAndAcquireFence (texture upload) failed: %s", sdl.GetError())
+		sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
+		sdl.ReleaseGPUTexture(app.device, out.texture)
+		return {}, false
+	}
+	defer sdl.ReleaseGPUFence(app.device, fence)
+
+	if !sdl.WaitForGPUFences(app.device, true, &fence, 1) {
+		fmt.eprintfln("WaitForGPUFences (texture upload) failed: %s", sdl.GetError())
+		sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
+		sdl.ReleaseGPUTexture(app.device, out.texture)
+		return {}, false
+	}
+
+	sdl.ReleaseGPUTransferBuffer(app.device, tbuf)
+
 	return out, true
 }
 
-destroy_character_data :: proc(data: ^Character_Data) {
+destroy_character_data :: proc(app: ^App, data: ^Character_Data) {
 	if data.texture != nil {
-		sdl.DestroyTexture(data.texture)
+		// Ensure no in-flight draw command is still sampling this texture.
+		if app != nil && app.device != nil {
+			_ = sdl.WaitForGPUIdle(app.device)
+		}
+		sdl.ReleaseGPUTexture(app.device, data.texture)
 	}
 	data^ = {}
 }

engine/sprite.odin

@@ -1,5 +1,6 @@
 package engine
 
+import "core:mem"
 import sdl "vendor:sdl3"
 
 Vec2 :: [2]f32
@@ -26,26 +27,105 @@ update_sprite :: proc(sprite: ^Sprite, dt: f32) {
 	_ = dt
 }
 
-draw_sprite :: proc(renderer: ^sdl.Renderer, sprite: ^Sprite) {
-	assert(sprite.data != nil)
+to_clip :: proc(px, py, sw, sh: f32) -> [2]f32 {
+	return {
+		px / sw * 2 - 1,
+		1 - py / sh * 2, // flip y (window pixels are y-down)
+	}
+}
+
+draw_sprite :: proc(app: ^App, sprite: ^Sprite) {
+	if app.render_pass == nil || app.cmd == nil || app.swapchain_texture == nil {
+		return // begin_frame may have skipped (minimized window, etc.)
+	}
+	if sprite == nil || sprite.data == nil || sprite.data.texture == nil {
+		return
+	}
+
 	rect, ok := character_frame_rect(sprite.data, sprite.clip, sprite.frame)
 	if !ok {
 		return
 	}
 
-	w := f32(rect[2])
-	h := f32(rect[3])
-	dst := sdl.FRect {
-		x = sprite.position.x - w * 0.5,
-		y = sprite.position.y - h,
-		w = w,
-		h = h,
+	fw := f32(rect[2])
+	fh := f32(rect[3])
+
+	// Feet-centered placement, same as renderer version
+	x0_px := sprite.position.x - fw * 0.5
+	y0_px := sprite.position.y - fh
+	x1_px := x0_px + fw
+	y1_px := y0_px + fh
+
+	sw := f32(app.swapchain_w)
+	sh := f32(app.swapchain_h)
+	p0 := to_clip(x0_px, y0_px, sw, sh) // top-left
+	p1 := to_clip(x1_px, y0_px, sw, sh) // top-right
+	p2 := to_clip(x1_px, y1_px, sw, sh) // bottom-right
+	p3 := to_clip(x0_px, y1_px, sw, sh) // bottom-left
+
+	tex_w := f32(sprite.data.width)
+	tex_h := f32(sprite.data.height)
+	u0 := f32(rect[0]) / tex_w
+	v0 := f32(rect[1]) / tex_h
+	u1 := f32(rect[0] + rect[2]) / tex_w
+	v1 := f32(rect[1] + rect[3]) / tex_h
+
+	// Two triangles: (0,1,2) and (0,2,3)
+	verts := [6]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}},
 	}
-	src := sdl.FRect {
-		x = f32(rect[0]),
-		y = f32(rect[1]),
-		w = w,
-		h = h,
+
+	map_ptr := sdl.MapGPUTransferBuffer(app.device, app.transfer_buffer, false)
+	if map_ptr == nil {
+		return
 	}
-	sdl.RenderTexture(renderer, sprite.data.texture, &src, &dst)
+	mem.copy(map_ptr, raw_data(verts[:]), size_of(verts))
+	sdl.UnmapGPUTransferBuffer(app.device, app.transfer_buffer)
+
+	// IMPORTANT: SDL does not allow beginning a copy pass while a render pass
+	// is active on the same command buffer. Upload on a separate command buffer.
+	copy_cmd := sdl.AcquireGPUCommandBuffer(app.device)
+	if copy_cmd == nil {
+		return
+	}
+	copy_pass := sdl.BeginGPUCopyPass(copy_cmd)
+
+	src := sdl.GPUTransferBufferLocation {
+		transfer_buffer = app.transfer_buffer,
+		offset          = 0,
+	}
+	dst := sdl.GPUBufferRegion {
+		buffer = app.vertex_buffer,
+		offset = 0,
+		size   = u32(size_of(verts)),
+	}
+	sdl.UploadToGPUBuffer(copy_pass, src, dst, false)
+	sdl.EndGPUCopyPass(copy_pass)
+	fence := sdl.SubmitGPUCommandBufferAndAcquireFence(copy_cmd)
+	if fence == nil {
+		return
+	}
+	defer sdl.ReleaseGPUFence(app.device, fence)
+	if !sdl.WaitForGPUFences(app.device, true, &fence, 1) {
+		return
+	}
+
+	sampler_binding := sdl.GPUTextureSamplerBinding {
+		texture = sprite.data.texture,
+		sampler = app.sampler,
+	}
+	sdl.BindGPUFragmentSamplers(app.render_pass, 0, &sampler_binding, 1)
+
+	vb_binding := sdl.GPUBufferBinding {
+		buffer = app.vertex_buffer,
+		offset = 0,
+	}
+	sdl.BindGPUVertexBuffers(app.render_pass, 0, &vb_binding, 1)
+
+	sdl.DrawGPUPrimitives(app.render_pass, 6, 1, 0, 0)
 }

examples/toad/main.odin

@@ -4,25 +4,19 @@ import eng "pkg:engine"
 
 main :: proc() {
 	app: eng.App
-	if !eng.init(&app, "toad example", 800, 600) {
-		return
-	}
+	if !eng.init(&app, "toad", 800, 600) do return
 	defer eng.shutdown(&app)
 
-	data, ok := eng.load_character_data(
-		app.renderer,
-		"assets_baked/characters/toad/toad.char.json",
-	)
-	if !ok {
-		return
-	}
-	defer eng.destroy_character_data(&data)
+	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)
 
 	toad := eng.spawn_sprite(&data, {400, 500}, "idle", 0)
 
-	for eng.pump_events() {
+	for eng.events() {
 		eng.begin_frame(&app)
-		eng.draw_sprite(app.renderer, &toad)
+		eng.draw_sprite(&app, &toad)
 		eng.end_frame(&app)
 	}
 }

shaders/sprite.frag.glsl

@@ -0,0 +1,10 @@
+#version 450
+
+layout(set = 2, binding = 0) uniform sampler2D u_tex; // SDL_GPU fragment sampler slot 0
+
+layout(location = 0) in vec2 v_uv;
+layout(location = 0) out vec4 out_color;
+
+void main() {
+    out_color = texture(u_tex, v_uv);
+}

shaders/sprite.vert.glsl

@@ -0,0 +1,11 @@
+#version 450
+
+layout(location = 0) in vec2 in_pos;
+layout(location = 1) in vec2 in_uv;
+
+layout(location = 0) out vec2 v_uv;
+
+void main() {
+  v_uv = in_uv;
+  gl_Position = vec4(in_pos, 0.0, 1.0);
+}