Create/Update assets for version 13w43a

assets/minecraft/shaders/program/sobel.fsh

@@ -0,0 +1,20 @@
+#version 120
+
+uniform sampler2D DiffuseSampler;
+
+varying vec2 texCoord;
+varying vec2 oneTexel;
+
+void main(){
+    vec4 center = texture2D(DiffuseSampler, texCoord);
+    vec4 left   = texture2D(DiffuseSampler, texCoord - vec2(oneTexel.x, 0.0));
+    vec4 right  = texture2D(DiffuseSampler, texCoord + vec2(oneTexel.x, 0.0));
+    vec4 up     = texture2D(DiffuseSampler, texCoord - vec2(0.0, oneTexel.y));
+    vec4 down   = texture2D(DiffuseSampler, texCoord + vec2(0.0, oneTexel.y));
+    vec4 leftDiff  = center - left;
+    vec4 rightDiff = center - right;
+    vec4 upDiff    = center - up;
+    vec4 downDiff  = center - down;
+    vec4 total = clamp(leftDiff + rightDiff + upDiff + downDiff, 0.0, 1.0);
+    gl_FragColor = vec4(total.rgb, center.a);
+}