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

[nageru] / equations.frag

diff --git a/equations.frag b/equations.frag
index 51e1394e13bfcc00d37ac70d3c8366a195e5930d..6c4fa5d2c9bb847226f75c7b3504cd5f3e53d6d2 100644 (file)
--- a/equations.frag
+++ b/equations.frag
@@ -14,6 +14,8 @@ uniform float delta;
 // Relative weighting of gradient term.
 uniform float gamma;
 
+uniform bool zero_diff_flow;
+
 // Similar to packHalf2x16, but the two values share exponent, and are stored
 // as 12-bit fixed point numbers multiplied by that exponent (the leading one
 // can't be implicit in this kind of format). This allows us to store a much
@@ -56,9 +58,14 @@ uint pack_floats_shared(float a, float b)
 void main()
 {
        // Read the flow (on top of the u0/v0 flow).
-       vec2 diff_flow = texture(diff_flow_tex, tc).xy;
-       float du = diff_flow.x;
-       float dv = diff_flow.y;
+       float du, dv;
+       if (zero_diff_flow) {
+               du = dv = 0.0f;
+       } else {
+               vec2 diff_flow = texture(diff_flow_tex, tc).xy;
+               du = diff_flow.x;
+               dv = diff_flow.y;
+       }
 
        // Read the first derivatives.
        vec2 I_x_y = texture(I_x_y_tex, tc).xy;