Create/Update assets for version 1.17.1

assets/minecraft/shaders/include/fog.glsl

@@ -0,0 +1,20 @@
+#version 150
+
+vec4 linear_fog(vec4 inColor, float vertexDistance, float fogStart, float fogEnd, vec4 fogColor) {
+    if (vertexDistance <= fogStart) {
+        return inColor;
+    }
+
+    float fogValue = vertexDistance < fogEnd ? smoothstep(fogStart, fogEnd, vertexDistance) : 1.0;
+    return vec4(mix(inColor.rgb, fogColor.rgb, fogValue * fogColor.a), inColor.a);
+}
+
+float linear_fog_fade(float vertexDistance, float fogStart, float fogEnd) {
+    if (vertexDistance <= fogStart) {
+        return 1.0;
+    } else if (vertexDistance >= fogEnd) {
+        return 0.0;
+    }
+
+    return smoothstep(fogEnd, fogStart, vertexDistance);
+}