PMREMGenerator: Improve GGX VNDF accuracy and match Blender roughness (#32311)

src/extras/PMREMGenerator.js

@@ -532,7 +532,7 @@ class PMREMGenerator {
 		const incrementalRoughness = Math.sqrt( targetRoughness * targetRoughness - sourceRoughness * sourceRoughness );
 
 		// Apply blur strength mapping for better quality across the roughness range
-		const blurStrength = 0.05 + targetRoughness * 0.95;
+		const blurStrength = 0.0 + targetRoughness * 1.25;
 		const adjustedRoughness = incrementalRoughness * blurStrength;
 
 		// Calculate viewport position based on output LOD level

src/renderers/common/extras/PMREMGenerator.js

@@ -663,7 +663,7 @@ class PMREMGenerator {
 		const incrementalRoughness = Math.sqrt( targetRoughness * targetRoughness - sourceRoughness * sourceRoughness );
 
 		// Apply blur strength mapping for better quality across the roughness range
-		const blurStrength = 0.05 + targetRoughness * 0.95;
+		const blurStrength = 0.0 + targetRoughness * 1.25;
 		const adjustedRoughness = incrementalRoughness * blurStrength;
 
 		// Calculate viewport position based on output LOD level