From 164ffa2b4f6c864e4bd8155c735a1672f6ac9e8b Mon Sep 17 00:00:00 2001
From: vlj <vljn@ovi.com>
Date: Tue, 3 Jun 2014 03:14:39 +0200
Subject: [PATCH] Spped up SSAO

Avoid using cos/sin too much, use sum of cos/sin formula instead.
---
 data/shaders/ssao.frag | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/data/shaders/ssao.frag b/data/shaders/ssao.frag
index 22c68a620..7c0b10bac 100644
--- a/data/shaders/ssao.frag
+++ b/data/shaders/ssao.frag
@@ -59,11 +59,15 @@ void main(void)
     float phi = 30. * (x ^ y) + 10. * x * y;
     float bl = 0.0;
 
+    float theta = 2. * 3.14 * tau * .5 * invSamples + phi;
+    vec2 rotations = vec2(cos(theta), sin(theta)) * screen;
+    vec2 offset = vec2(cos(invSamples), sin(invSamples));
+
     for(int i = 0; i < SAMPLES; ++i) {
         float alpha = (i + .5) * invSamples;
-        float theta = 2. * 3.14 * tau * alpha + phi;
+        rotations = vec2(rotations.x * offset.x - rotations.y * offset.y, rotations.x * offset.y + rotations.y * offset.x);
         float h = r * alpha;
-        vec2 offset = h * vec2(cos(theta), sin(theta)) * screen;
+        vec2 offset = h * rotations;
 
         float m = round(log2(h) + 6);
         ivec2 ioccluder_uv = ivec2(x, y) + ivec2(offset);