Pack the gradients and image together into a single 32-bit texture; seems to help...

[nageru] / sobel.frag

diff --git a/sobel.frag b/sobel.frag
index 90c6d8a93c895368b45cbb18480148cd5583559c..3066300dfec5f5ceb29e795bc8f779a4511a1855 100644 (file)
--- a/sobel.frag
+++ b/sobel.frag
@@ -1,10 +1,21 @@
 #version 450 core
 
 in vec2 tc;
-out vec2 gradients;
+out uint packed_gradients;
 
 uniform sampler2D tex;
 
+uint pack_gradients(float x, float y, float v)
+{
+       x = clamp(x, -0.5f, 0.5f);
+       y = clamp(y, -0.5f, 0.5f);
+
+       uint vi = uint(round(v * 255.0f));
+       uint xi = uint(round((x + 0.5f) * 4095.0f));
+       uint yi = uint(round((y + 0.5f) * 4095.0f));
+       return vi | (xi << 8) | (yi << 20);
+}
+
 void main()
 {
        // There are two common Sobel filters, horizontal and vertical
@@ -36,10 +47,18 @@ void main()
        float right        = textureOffset(tex, tc, ivec2( 1,  0)).x;
        float bottom_right = textureOffset(tex, tc, ivec2( 1, -1)).x;
 
+       vec2 gradients;
        gradients.x = (top_right + 2.0f * right + bottom_right) - (top_left + 2.0f * left + bottom_left);
        gradients.y = (top_left + 2.0 * top + top_right) - (bottom_left + 2.0f * bottom + bottom_right);
 
        // Normalize so that we have a normalized unit of intensity levels per pixel.
        gradients.x *= 0.125;
        gradients.y *= 0.125;
+
+       // Also store the actual pixel value, so that we get it “for free”
+       // when we sample the gradients in motion_search.frag later.
+       float center = texture(tex, tc).x;
+
+       // Pack everything into a single 32-bit value, using simple fixed-point.
+       packed_gradients = pack_gradients(gradients.x, gradients.y, center);
 }