Create/Update assets for version 21w13a

assets/minecraft/shaders/program/outline.fsh

@@ -0,0 +1,23 @@
+#version 150
+
+uniform sampler2D DiffuseSampler;
+
+in vec2 texCoord;
+in vec2 oneTexel;
+
+out vec4 fragColor;
+
+void main(){
+    vec4 center = texture(DiffuseSampler, texCoord);
+    vec4 up     = texture(DiffuseSampler, texCoord + vec2(        0.0, -oneTexel.y));
+    vec4 down   = texture(DiffuseSampler, texCoord + vec2( oneTexel.x,         0.0));
+    vec4 left   = texture(DiffuseSampler, texCoord + vec2(-oneTexel.x,         0.0));
+    vec4 right  = texture(DiffuseSampler, texCoord + vec2(        0.0,  oneTexel.y));
+    vec4 uDiff = center - up;
+    vec4 dDiff = center - down;
+    vec4 lDiff = center - left;
+    vec4 rDiff = center - right;
+    vec4 sum = uDiff + dDiff + lDiff + rDiff;
+    vec3 clamped = clamp(center.rgb - sum.rgb, 0.0, 1.0);
+    fragColor = vec4(clamped, 1.0);
+}