Merge pull request #18935 from stevesan/blurfix

Refactored PMREM blur shader due to apparent compiler bug

src/extras/PMREMGenerator.js

@@ -611,27 +611,28 @@ ${_getEncodings()}
 #define ENVMAP_TYPE_CUBE_UV
 #include <cube_uv_reflection_fragment>
 
+vec3 getSample(float theta, vec3 axis) {
+	float cosTheta = cos(theta);
+	// Rodrigues' axis-angle rotation
+	vec3 sampleDirection = vOutputDirection * cosTheta
+		+ cross(axis, vOutputDirection) * sin(theta)
+		+ axis * dot(axis, vOutputDirection) * (1.0 - cosTheta);
+	return bilinearCubeUV(envMap, sampleDirection, mipInt);
+}
+
 void main() {
+	vec3 axis = latitudinal ? poleAxis : cross(poleAxis, vOutputDirection);
+	if (all(equal(axis, vec3(0.0))))
+		axis = vec3(vOutputDirection.z, 0.0, - vOutputDirection.x );
+	axis = normalize(axis);
 	gl_FragColor = vec4(0.0);
-	for (int i = 0; i < n; i++) {
+	gl_FragColor.rgb += weights[0] * getSample(0.0, axis);
+	for (int i = 1; i < n; i++) {
 		if (i >= samples)
 			break;
-		for (int dir = -1; dir < 2; dir += 2) {
-			if (i == 0 && dir == 1)
-				continue;
-			vec3 axis = latitudinal ? poleAxis : cross(poleAxis, vOutputDirection);
-			if (all(equal(axis, vec3(0.0))))
-				axis = cross(vec3(0.0, 1.0, 0.0), vOutputDirection);
-			axis = normalize(axis);
-			float theta = dTheta * float(dir * i);
-			float cosTheta = cos(theta);
-			// Rodrigues' axis-angle rotation
-			vec3 sampleDirection = vOutputDirection * cosTheta
-					+ cross(axis, vOutputDirection) * sin(theta)
-					+ axis * dot(axis, vOutputDirection) * (1.0 - cosTheta);
-			gl_FragColor.rgb +=
-					weights[i] * bilinearCubeUV(envMap, sampleDirection, mipInt);
-		}
+		float theta = dTheta * float(i);
+		gl_FragColor.rgb += weights[i] * getSample(-1.0 * theta, axis);
+		gl_FragColor.rgb += weights[i] * getSample(theta, axis);
 	}
 	gl_FragColor = linearToOutputTexel(gl_FragColor);
 }