Zachary Levy
22 lines
936 B
GLSL
22 lines
936 B
GLSL
#version 450 core
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// Fullscreen-triangle vertex shader for the backdrop downsample and H-blur sub-passes.
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// Emits a single triangle covering NDC [-1,1]^2; the rasterizer clips edges outside.
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// No vertex buffer; uses gl_VertexIndex to pick corners.
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//
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// The CPU sets the viewport (and matching scissor) per layer-bracket to limit work to
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// the union AABB of the layer's backdrop primitives, expanded by 3*max_sigma and
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// clamped to swapchain bounds. The fragment shader uses gl_FragCoord (absolute pixel
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// space in the bound target) plus an inv-size uniform to compute its own UVs — see
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// each fragment shader for the per-pass sampling math.
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void main() {
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// gl_VertexIndex 0 -> ( -1, -1)
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// gl_VertexIndex 1 -> ( 3, -1)
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// gl_VertexIndex 2 -> ( -1, 3)
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vec2 ndc = vec2(
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(gl_VertexIndex == 1) ? 3.0 : -1.0,
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(gl_VertexIndex == 2) ? 3.0 : -1.0);
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gl_Position = vec4(ndc, 0.0, 1.0);
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}
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