6 uniform sampler2D diff_flow_tex, smoothness_x_tex, smoothness_y_tex;
7 uniform usampler2D equation_tex;
9 // See pack_floats_shared() in equations.frag.
10 vec2 unpack_floats_shared(uint c)
12 // Recover the exponent, and multiply it in. Add one because
13 // we have denormalized mantissas, then another one because we
14 // already reduced the exponent by one. Then subtract 20, because
15 // we are going to shift up the number by 20 below to recover the sign bits.
16 float normalizer = uintBitsToFloat(((c >> 1) & 0x7f800000u) - (18 << 23));
17 normalizer *= (1.0 / 2047.0);
19 // Shift the values up so that we recover the sign bit, then normalize.
20 float a = int(uint(c & 0x000fffu) << 20) * normalizer;
21 float b = int(uint(c & 0xfff000u) << 8) * normalizer;
28 uvec4 equation = texture(equation_tex, tc);
29 float inv_A11 = uintBitsToFloat(equation.x);
30 float A12 = uintBitsToFloat(equation.y);
31 float inv_A22 = uintBitsToFloat(equation.z);
32 vec2 b = unpack_floats_shared(equation.w);
34 // Subtract the missing terms from the right-hand side
35 // (it couldn't be done earlier, because we didn't know
36 // the values of the neighboring pixels; they change for
37 // each SOR iteration).
38 // TODO: Multiply by some gamma.
39 float smooth_l = textureOffset(smoothness_x_tex, tc, ivec2(-1, 0)).x;
40 float smooth_r = texture(smoothness_x_tex, tc).x;
41 float smooth_d = textureOffset(smoothness_y_tex, tc, ivec2( 0, -1)).x;
42 float smooth_u = texture(smoothness_y_tex, tc).x;
43 b += smooth_l * textureOffset(diff_flow_tex, tc, ivec2(-1, 0)).xy;
44 b += smooth_r * textureOffset(diff_flow_tex, tc, ivec2( 1, 0)).xy;
45 b += smooth_d * textureOffset(diff_flow_tex, tc, ivec2( 0, -1)).xy;
46 b += smooth_u * textureOffset(diff_flow_tex, tc, ivec2( 0, 1)).xy;
48 // FIXME: omega=1.6 seems to make our entire system diverge.
49 // Is this because we do Gauss-Seidel instead of Jacobi?
50 // Figure out what's going on.
51 const float omega = 1.0;
52 diff_flow = texture(diff_flow_tex, tc).xy;
54 // From https://en.wikipedia.org/wiki/Successive_over-relaxation.
55 float sigma_u = A12 * diff_flow.y;
56 diff_flow.x += omega * ((b.x - sigma_u) * inv_A11 - diff_flow.x);
57 float sigma_v = A12 * diff_flow.x;
58 diff_flow.y += omega * ((b.y - sigma_v) * inv_A22 - diff_flow.y);