46 lines
1.3 KiB
GLSL
46 lines
1.3 KiB
GLSL
#version 440 core
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layout(push_constant) uniform Params {
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// Size of the source image.
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uint source_size_xy;
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// Offset to place the image at in the target texture.
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//
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// Origin is the top-left.
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uint target_offset_xy;
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// Size of the target texture.
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uint target_size_xy;
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};
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layout(location = 0) out vec2 source_coords;
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vec2 unpack(uint xy) {
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return vec2(xy & 0xFFFF, (xy >> 16) & 0xFFFF);
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}
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void main() {
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vec2 source_size = unpack(source_size_xy);
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vec2 target_offset = unpack(target_offset_xy);
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vec2 target_size = unpack(target_size_xy);
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// Generate rectangle (counter clockwise triangles)
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//
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// 0 0 1 1 1 0
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float x_select = float(((uint(gl_VertexIndex) + 1u) / 3u) % 2u);
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// 1 0 0 0 1 1
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float y_select = float(((uint(gl_VertexIndex) + 5u) / 3u) % 2u);
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source_coords = vec2(
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// left -> right (on screen)
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mix(0.0, 1.0, x_select),
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// bottom -> top (on screen)
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mix(1.0, 0.0, y_select)
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) * source_size;
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vec2 target_coords_normalized = (target_offset + source_coords) / target_size;
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// Flip y and transform [0.0, 1.0] -> [-1.0, 1.0] to get NDC coordinates.
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vec2 v_pos = ((target_coords_normalized * 2.0) - vec2(1.0)) * vec2(1.0, -1.0);
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gl_Position = vec4(v_pos, 0.0, 1.0);
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}
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