fix: refractionTransmitted need linear space

Author: hhhhkrx

packages/shader-shaderlab/src/shaders/shadingPBR/BTDF.glsl

@@ -23,6 +23,9 @@
 
         // Sample the opaque texture to get the transmitted light
         vec3 refractionTransmitted = texture2D(camera_OpaqueTexture, refractionCoords).rgb;
+        #ifndef ENGINE_IS_COLORSPACE_GAMMA
+            refractionTransmitted = gammaToLinear(vec4(refractionTransmitted, 1.0)).rgb;
+        #endif
         refractionTransmitted *= brdfData.diffuseColor;
 
         // Use specularFGD as an approximation of the fresnel effect