group_bot/assets/voxygen/shaders/premultiply-alpha-vert.glsl

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2024-06-13 23:16:24 +00:00
#version 440 core
layout(push_constant) uniform Params {
// Size of the source image.
uint source_size_xy;
// Offset to place the image at in the target texture.
//
// Origin is the top-left.
uint target_offset_xy;
// Size of the target texture.
uint target_size_xy;
};
layout(location = 0) out vec2 source_coords;
vec2 unpack(uint xy) {
return vec2(xy & 0xFFFF, (xy >> 16) & 0xFFFF);
}
void main() {
vec2 source_size = unpack(source_size_xy);
vec2 target_offset = unpack(target_offset_xy);
vec2 target_size = unpack(target_size_xy);
// Generate rectangle (counter clockwise triangles)
//
// 0 0 1 1 1 0
float x_select = float(((uint(gl_VertexIndex) + 1u) / 3u) % 2u);
// 1 0 0 0 1 1
float y_select = float(((uint(gl_VertexIndex) + 5u) / 3u) % 2u);
source_coords = vec2(
// left -> right (on screen)
mix(0.0, 1.0, x_select),
// bottom -> top (on screen)
mix(1.0, 0.0, y_select)
) * source_size;
vec2 target_coords_normalized = (target_offset + source_coords) / target_size;
// Flip y and transform [0.0, 1.0] -> [-1.0, 1.0] to get NDC coordinates.
vec2 v_pos = ((target_coords_normalized * 2.0) - vec2(1.0)) * vec2(1.0, -1.0);
gl_Position = vec4(v_pos, 0.0, 1.0);
}