Fix an issue where we would lose >1 ms for computing flow on NVIDIA, due to lack...

[nageru] / sor.frag

diff --git a/sor.frag b/sor.frag
index fbcc2e4ca8b8532b829a7c653b88757310448fba..2b68597de3029c912eea11a37f4c60462deaa5ea 100644 (file)
--- a/sor.frag
+++ b/sor.frag
@@ -6,9 +6,10 @@ out vec2 diff_flow;
 
 uniform sampler2D diff_flow_tex, smoothness_x_tex, smoothness_y_tex;
 uniform usampler2D equation_tex;
-uniform vec2 image_size;
 uniform int phase;
 
+uniform bool zero_diff_flow;
+
 // See pack_floats_shared() in equations.frag.
 vec2 unpack_floats_shared(uint c)
 {
@@ -44,21 +45,25 @@ void main()
        float inv_A22 = uintBitsToFloat(equation.z);
        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).
-       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;
+       if (zero_diff_flow) {
+               diff_flow = vec2(0.0f);
+       } else {
+               // 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).
+               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;
+               diff_flow = texture(diff_flow_tex, tc).xy;
+       }
 
        const float omega = 1.8;  // Marginally better than 1.6, it seems.
-       diff_flow = texture(diff_flow_tex, tc).xy;
 
        // From https://en.wikipedia.org/wiki/Successive_over-relaxation.
        float sigma_u = A12 * diff_flow.y;