Set the default fallback material as Phong.

[0mdc]

Motivation and Context

The default materials were changed to PBR here, including the default fallback material. When rendering with depth cameras, no texture is loaded from materials. The fallback material is instead applied to objects.

Because skinning only works with Phong, it breaks when the only sensors present in the simulation are depth.

This changes the default fallback material to Phong. We can revert this change when skinning support is added to PBR.

How Has This Been Tested

Tested locally on the SIRo HITL tool.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[jturner65]

LGTM. I can prune this if necessary once I get the PBR skinning to work.

[eundersander]

As I understand, this is reverting a portion of the recent #2235 , so I imagine it's fairly safe. I'm not too familiar with the current state of materials or what the fallbackMaterial is used for. I'll defer to John and Mikael.