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#include "common.glsl"
layout(binding = 0) uniform sampler2D image;
layout(location = 0) in vec2 grid_pos;
layout(location = 1) in vec2 cell_offset;
layout(location = 2) in vec4 source_rect;
layout(location = 3) in vec2 dest_size;
out vec2 tex_coord;
void main() {
int vid = gl_VertexID;
// We use a triangle strip with 4 vertices to render quads,
// so we determine which corner of the cell this vertex is in
// based on the vertex ID.
//
// 0 --> 1
// | .'|
// | / |
// | L |
// 2 --> 3
//
// 0 = top-left (0, 0)
// 1 = top-right (1, 0)
// 2 = bot-left (0, 1)
// 3 = bot-right (1, 1)
vec2 corner;
corner.x = float(vid == 1 || vid == 3);
corner.y = float(vid == 2 || vid == 3);
// The texture coordinates start at our source x/y
// and add the width/height depending on the corner.
tex_coord = source_rect.xy;
tex_coord += source_rect.zw * corner;
// Normalize the coordinates.
tex_coord /= textureSize(image, 0);
// The position of our image starts at the top-left of the grid cell and
// adds the source rect width/height components.
vec2 image_pos = (cell_size * grid_pos) + cell_offset;
image_pos += dest_size * corner;
gl_Position = projection_matrix * vec4(image_pos.xy, 1.0, 1.0);
}
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