encourage experimentation with edge detewction shader

Author: monkstone

video_filtering/README.md

@@ -0,0 +1,8 @@
+### Experiment with different edge-detection algorithms
+In the provide example the sketch uses a sobel filter
+
+`#define SOBEL`
+
+Alernatives are `KAYYALI_NESW, KAYYALI_SENW, PREWITT, ROBERTSCROSS, SCHARR`
+
+Modify `edge_detect.glsl` directly to use these alternative algorithms included in the shader.