* Materials can now specify a shadow strength factor
Materials have a new property: shadowStrength that can be used to
attenuate all shadows received by this material. e.g.:
```
void material(inout MaterialInputs material) {
prepareMaterial(material);
material. shadowStrength = 0.1;
}
```
FIXES=[391663042]
Co-authored-by: Powei Feng <powei@google.com>
---------
Co-authored-by: Powei Feng <powei@google.com>