From 6911c97816e4dde727ed3aa0fa0631c4047d2bd6 Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Sat, 4 Aug 2018 14:43:22 +0200 Subject: [PATCH] Microoptimization in the SOR fragment shader. --- sor.frag | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/sor.frag b/sor.frag index 047526c..e1f86bb 100644 --- a/sor.frag +++ b/sor.frag @@ -67,8 +67,12 @@ void main() float inv_A22 = uintBitsToFloat(equation.z); vec2 b = unpack_floats_shared(equation.w); + const float omega = 1.8; // Marginally better than 1.6, it seems. + if (zero_diff_flow) { - diff_flow = vec2(0.0f); + // Simplified version of the code below, assuming diff_flow == 0.0f everywhere. + diff_flow.x = omega * b.x * inv_A11; + diff_flow.y = omega * b.y * inv_A22; } else { // Subtract the missing terms from the right-hand side // (it couldn't be done earlier, because we didn't know @@ -83,13 +87,11 @@ void main() 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. - - // From https://en.wikipedia.org/wiki/Successive_over-relaxation. - float sigma_u = A12 * diff_flow.y; - diff_flow.x += omega * ((b.x - sigma_u) * inv_A11 - diff_flow.x); - float sigma_v = A12 * diff_flow.x; - diff_flow.y += omega * ((b.y - sigma_v) * inv_A22 - diff_flow.y); + // From https://en.wikipedia.org/wiki/Successive_over-relaxation. + float sigma_u = A12 * diff_flow.y; + diff_flow.x += omega * ((b.x - sigma_u) * inv_A11 - diff_flow.x); + float sigma_v = A12 * diff_flow.x; + diff_flow.y += omega * ((b.y - sigma_v) * inv_A22 - diff_flow.y); + } } -- 2.39.2