6 flat out float mean_diff;
8 uniform int width_patches;
9 uniform vec2 patch_size; // In 0..1 coordinates.
10 uniform vec2 patch_spacing; // In 0..1 coordinates.
11 uniform sampler2D flow_tex;
15 int patch_x = gl_InstanceID % width_patches;
16 int patch_y = gl_InstanceID / width_patches;
18 // Increase the patch size a bit; since patch spacing is not necessarily
19 // an integer number of pixels, and we don't use conservative rasterization,
20 // we could be missing the outer edges of the patch. And it seemingly helps
21 // a little bit in general to have some more candidates as well -- although
22 // this is measured without variational refinement, so it might be moot
25 // Tihs maps [0.0,1.0] to [-0.25 to 1.25), ie. extends the patch by 25% in
27 vec2 grown_pos = (position * 1.5) - vec2(0.25, 0.25);
29 image_pos = patch_spacing * ivec2(patch_x, patch_y) + patch_size * grown_pos;
31 // Find the flow value for this patch, and send it on to the fragment shader.
32 vec3 flow_du_and_mean_diff = texelFetch(flow_tex, ivec2(patch_x, patch_y), 0).xyz;
33 flow_du = flow_du_and_mean_diff.xy;
34 mean_diff = flow_du_and_mean_diff.z;
36 // The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is:
38 // 2.000 0.000 0.000 -1.000
39 // 0.000 2.000 0.000 -1.000
40 // 0.000 0.000 -2.000 -1.000
41 // 0.000 0.000 0.000 1.000
42 gl_Position = vec4(2.0 * image_pos.x - 1.0, 2.0 * image_pos.y - 1.0, -1.0, 1.0);