3 layout(location=0) in vec2 position;
4 out vec2 tc, tc_left, tc_down;
5 out vec2 equation_tc_assuming_left, equation_tc_assuming_right;
6 out float element_x_idx;
7 out float element_sum_idx;
9 uniform sampler2D diff_flow_tex, diffusivity_tex;
10 uniform usampler2D equation_red_tex;
14 // The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is:
16 // 2.000 0.000 0.000 -1.000
17 // 0.000 2.000 0.000 -1.000
18 // 0.000 0.000 -2.000 -1.000
19 // 0.000 0.000 0.000 1.000
20 gl_Position = vec4(2.0 * position.x - 1.0, 2.0 * position.y - 1.0, -1.0, 1.0);
22 tc_left = vec2(tc.x - 0.5f / textureSize(diffusivity_tex, 0).x, tc.y);
23 tc_down = vec2(tc.x, tc.y - 0.5f / textureSize(diffusivity_tex, 0).y);
25 // The equation textures have half the horizontal width, so we need to adjust the texel centers.
26 // It becomes extra tricky since the SOR texture might be of odd size, and then
27 // the equation texture is not exactly half the size.
28 vec2 element_idx = position * textureSize(diff_flow_tex, 0) - 0.5f;
29 float equation_texel_number_assuming_left = element_idx.x / 2.0f;
30 float equation_texel_number_assuming_right = (element_idx.x - 1.0f) / 2.0f;
31 equation_tc_assuming_left.x = (equation_texel_number_assuming_left + 0.5f) / textureSize(equation_red_tex, 0).x;
32 equation_tc_assuming_right.x = (equation_texel_number_assuming_right + 0.5f) / textureSize(equation_red_tex, 0).x;
33 equation_tc_assuming_left.y = tc.y;
34 equation_tc_assuming_right.y = tc.y;
36 element_x_idx = element_idx.x;
37 element_sum_idx = element_idx.x + element_idx.y;