uniform sampler2D diff_flow_tex, smoothness_x_tex, smoothness_y_tex;
uniform usampler2D equation_tex;
+// See pack_floats_shared() in equations.frag.
+vec2 unpack_floats_shared(uint c)
+{
+ // Recover the exponent, and multiply it in. Add one because
+ // we have denormalized mantissas, then another one because we
+ // already reduced the exponent by one. Then subtract 20, because
+ // we are going to shift up the number by 20 below to recover the sign bits.
+ float normalizer = uintBitsToFloat(((c >> 1) & 0x7f800000u) - (18 << 23));
+ normalizer *= (1.0 / 2047.0);
+
+ // Shift the values up so that we recover the sign bit, then normalize.
+ float a = int(uint(c & 0x000fffu) << 20) * normalizer;
+ float b = int(uint(c & 0xfff000u) << 8) * normalizer;
+
+ return vec2(a, b);
+}
+
void main()
{
uvec4 equation = texture(equation_tex, tc);
float inv_A11 = uintBitsToFloat(equation.x);
float A12 = uintBitsToFloat(equation.y);
float inv_A22 = uintBitsToFloat(equation.z);
- vec2 b = unpackHalf2x16(equation.w);
+ vec2 b = unpack_floats_shared(equation.w);
// Subtract the missing terms from the right-hand side
// (it couldn't be done earlier, because we didn't know
// the values of the neighboring pixels; they change for
// each SOR iteration).
- // TODO: Multiply by some gamma.
float smooth_l = textureOffset(smoothness_x_tex, tc, ivec2(-1, 0)).x;
float smooth_r = texture(smoothness_x_tex, tc).x;
float smooth_d = textureOffset(smoothness_y_tex, tc, ivec2( 0, -1)).x;
float smooth_u = texture(smoothness_y_tex, tc).x;
- b -= smooth_l * textureOffset(diff_flow_tex, tc, ivec2(-1, 0)).xy;
- b -= smooth_r * textureOffset(diff_flow_tex, tc, ivec2( 1, 0)).xy;
- b -= smooth_d * textureOffset(diff_flow_tex, tc, ivec2( 0, -1)).xy;
- b -= smooth_u * textureOffset(diff_flow_tex, tc, ivec2( 0, 1)).xy;
+ b += smooth_l * textureOffset(diff_flow_tex, tc, ivec2(-1, 0)).xy;
+ b += smooth_r * textureOffset(diff_flow_tex, tc, ivec2( 1, 0)).xy;
+ b += smooth_d * textureOffset(diff_flow_tex, tc, ivec2( 0, -1)).xy;
+ b += smooth_u * textureOffset(diff_flow_tex, tc, ivec2( 0, 1)).xy;
- const float omega = 1.6;
+ // FIXME: omega=1.6 seems to make our entire system diverge.
+ // Is this because we do Gauss-Seidel instead of Jacobi?
+ // Figure out what's going on.
+ const float omega = 1.0;
diff_flow = texture(diff_flow_tex, tc).xy;
// From https://en.wikipedia.org/wiki/Successive_over-relaxation.