Create/Update assets for version 21w20a

assets/minecraft/shaders/program/outline_combine.fsh

@@ -0,0 +1,15 @@
+#version 150
+
+uniform sampler2D DiffuseSampler;
+uniform sampler2D OutlineSampler;
+
+in vec2 texCoord;
+in vec2 oneTexel;
+
+out vec4 fragColor;
+
+void main(){
+    vec4 diffuseTexel = texture(DiffuseSampler, texCoord);
+    vec4 outlineTexel = texture(OutlineSampler, texCoord);
+    fragColor = vec4(diffuseTexel.rgb + diffuseTexel.rgb * outlineTexel.rgb * vec3(0.75), 1.0);
+}