Create/Update assets for version 1.20.5-rc2

assets/minecraft/shaders/program/box_blur.fsh

@@ -0,0 +1,24 @@
+#version 150
+
+uniform sampler2D DiffuseSampler;
+
+in vec2 texCoord;
+in vec2 sampleStep;
+
+uniform float Radius;
+uniform float RadiusMultiplier;
+
+out vec4 fragColor;
+
+// This shader relies on GL_LINEAR sampling to reduce the amount of texture samples in half.
+// Instead of sampling each pixel position with a step of 1 we sample between pixels with a step of 2.
+// In the end we sample the last pixel with a half weight, since the amount of pixels to sample is always odd (actualRadius * 2 + 1).
+void main() {
+    vec4 blurred = vec4(0.0);
+    float actualRadius = round(Radius * RadiusMultiplier);
+    for (float a = -actualRadius + 0.5; a <= actualRadius; a += 2.0) {
+        blurred += texture(DiffuseSampler, texCoord + sampleStep * a);
+    }
+    blurred += texture(DiffuseSampler, texCoord + sampleStep * actualRadius) / 2.0;
+    fragColor = blurred / (actualRadius + 0.5);
+}