message: use the correct normal when calculating spotlight bias
  `vertex_worldNormal` should never be used directly, for one thing it's
  not guaranteed to be normalized.
diff: @@ -106,8 +106,8 @@ highp vec4 getSpotLightSpacePosition(uint index, highp float zLight) {
  // for spotlights, the bias depends on z
  float bias = shadowUniforms.shadows[index].normalBias * zLight;
  - return computeLightSpacePosition(getWorldPosition(),
  - vertex_worldNormal, dir, bias, lightFromWorldMatrix);
  + return computeLightSpacePosition(getWorldPosition(), getWorldNormalVector(),
  + dir, bias, lightFromWorldMatrix);
  }
  #endif
  