Compute diffusivity instead of smoothness, which saves a flow-size texture; shaves...

[nageru] / sor.frag

diff --git a/sor.frag b/sor.frag
index 2b68597de3029c912eea11a37f4c60462deaa5ea..91bf831e212a52b48204af6246d28c6419c60120 100644 (file)
--- a/sor.frag
+++ b/sor.frag
@@ -1,10 +1,10 @@
 #version 450 core
 
-in vec2 tc;
+in vec2 tc, tc_left, tc_down;
 in float element_sum_idx;
 out vec2 diff_flow;
 
-uniform sampler2D diff_flow_tex, smoothness_x_tex, smoothness_y_tex;
+uniform sampler2D diff_flow_tex, diffusivity_tex;
 uniform usampler2D equation_tex;
 uniform int phase;
 
@@ -27,6 +27,16 @@ vec2 unpack_floats_shared(uint c)
        return vec2(a, b);
 }
 
+float zero_if_outside_border(vec4 val)
+{
+       if (val.w < 1.0f) {
+               // We hit the border (or more like half-way to it), so zero smoothness.
+               return 0.0f;
+       } else {
+               return val.x;
+       }
+}
+
 void main()
 {
        // Red-black SOR: Every other pass, we update every other element in a
@@ -52,10 +62,10 @@ void main()
                // (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;
+               float smooth_l = zero_if_outside_border(texture(diffusivity_tex, tc_left));
+               float smooth_r = zero_if_outside_border(textureOffset(diffusivity_tex, tc_left, ivec2(1, 0)));
+               float smooth_d = zero_if_outside_border(texture(diffusivity_tex, tc_down));
+               float smooth_u = zero_if_outside_border(textureOffset(diffusivity_tex, tc_down, ivec2(0, 1)));
                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;