3 layout(location=0) in vec2 position;
6 flat out float mean_diff;
8 uniform vec2 patch_size; // In 0..1 coordinates.
9 uniform sampler2D flow_tex;
13 int patch_x = gl_InstanceID % textureSize(flow_tex, 0).x;
14 int patch_y = gl_InstanceID / textureSize(flow_tex, 0).x;
16 // Convert the patch index to being the full 0..1 range, to match where
17 // the motion search puts the patches. We don't bother with the locking
18 // to texel centers, though.
19 vec2 patch_center = ivec2(patch_x, patch_y) / (textureSize(flow_tex, 0) - 1.0);
21 // Increase the patch size a bit; since patch spacing is not necessarily
22 // an integer number of pixels, and we don't use conservative rasterization,
23 // we could be missing the outer edges of the patch. And it seemingly helps
24 // a little bit in general to have some more candidates as well -- although
25 // this is measured without variational refinement, so it might be moot
28 // This maps [0.0,1.0] to [-0.25,1.25], ie. extends the patch by 25% in
30 vec2 grown_pos = (position * 1.5) - 0.25;
32 image_pos = patch_center + patch_size * (grown_pos - 0.5f);
34 // Find the flow value for this patch, and send it on to the fragment shader.
35 vec3 flow_du_and_mean_diff = texelFetch(flow_tex, ivec2(patch_x, patch_y), 0).xyz;
36 flow_du = flow_du_and_mean_diff.xy;
37 mean_diff = flow_du_and_mean_diff.z;
39 // The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is:
41 // 2.000 0.000 0.000 -1.000
42 // 0.000 2.000 0.000 -1.000
43 // 0.000 0.000 -2.000 -1.000
44 // 0.000 0.000 0.000 1.000
45 gl_Position = vec4(2.0 * image_pos.x - 1.0, 2.0 * image_pos.y - 1.0, -1.0, 1.0);