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feat(examples): vk_triangle - a headless draw through Vulkan's graphics pipeline

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A Slang vertex and fragment shader draw a triangle into an image with dynamic rendering (no
render pass object: the pipeline names its colour format), image barriers move it to the
attachment and transfer layouts, and vkCmdCopyImageToBuffer reads it back into a PPM. It is
the path the Vulkan renderer's passes and screenshots take.

The corner comes from SV_VulkanVertexID: Slang compiles SV_VertexID to gl_VertexIndex -
gl_BaseVertex, which declares the draw-parameters capability.

Validation-clean and VKTRIANGLE OK on the RTX 3070 Ti (Windows) and the M4 Pro (MoltenVK),
13824 pixels covered on both.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Orkun ÇAKILKAYA 2026-09-15 11:37:47 +03:00
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examples/rendering/vk_triangle.slang Normal file
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// vk_triangle.slang — the first thing Ludic draws through Vulkan's graphics pipeline: three
// corners with no vertex buffer and a colour each, the rasteriser blending between them.
// The corner comes from SV_VulkanVertexID (gl_VertexIndex as it is): Slang compiles SV_VertexID
// to gl_VertexIndex - gl_BaseVertex, which needs the draw-parameters capability.
// slangc vk_triangle.slang -target spirv -profile spirv_1_5 -entry vsMain -stage vertex -o vk_triangle_vs.spv
// slangc vk_triangle.slang -target spirv -profile spirv_1_5 -entry fsMain -stage fragment -o vk_triangle_fs.spv
struct VOut
{
float4 pos : SV_Position;
float3 col : COLOR;
};
[shader("vertex")]
VOut vsMain(uint id : SV_VulkanVertexID)
{
// Vulkan's clip space has y pointing down, so the apex is at -y
static const float2 corners[3] = { float2(0.0, -0.6), float2(0.6, 0.6), float2(-0.6, 0.6) };
static const float3 colours[3] = { float3(1.0, 0.25, 0.1), float3(0.1, 1.0, 0.3), float3(0.2, 0.35, 1.0) };
VOut o;
o.pos = float4(corners[id], 0.0, 1.0);
o.col = colours[id];
return o;
}
[shader("fragment")]
float4 fsMain(VOut i) : SV_Target
{
return float4(i.col, 1.0);
}