Add a new effect that can do FFT/IFFT.

[movit] / fft_pass_effect.frag

diff --git a/fft_pass_effect.frag b/fft_pass_effect.frag
new file mode 100644 (file)
index 0000000..462a673
--- /dev/null
+++ b/fft_pass_effect.frag
@@ -0,0 +1,24 @@
+// DIRECTION_VERTICAL will be #defined to 1 if we are doing a vertical FFT,
+// and 0 otherwise.
+
+uniform float PREFIX(num_repeats);
+uniform sampler1D PREFIX(support_tex);
+
+vec4 FUNCNAME(vec2 tc) {
+#if DIRECTION_VERTICAL
+       vec4 support = texture1D(PREFIX(support_tex), tc.y * PREFIX(num_repeats));
+        vec4 c1 = INPUT(vec2(tc.x, 1.0 - (tc.y + support.x)));
+        vec4 c2 = INPUT(vec2(tc.x, 1.0 - (tc.y + support.y)));
+#else
+       vec4 support = texture1D(PREFIX(support_tex), tc.x * PREFIX(num_repeats));
+        vec4 c1 = INPUT(vec2(tc.x + support.x, tc.y));
+        vec4 c2 = INPUT(vec2(tc.x + support.y, tc.y));
+#endif
+       // Two complex additions and multiplications in parallel; essentially
+       //
+       //   result.xy = c1.xy + twiddle * c2.xy
+       //   result.zw = c1.zw + twiddle * c2.zw
+       //
+       // where * is complex multiplication.
+       return c1 + support.z * c2 + support.w * vec4(-c2.y, c2.x, -c2.w, c2.z);
+}