--[Bugfix/Refactor]-PBR Skin Rendering Prep/Bugfixes.

[jturner65]

Motivation and Context

This PR addresses the following issues/refactors :

• Some common Drawable functionality shared between GenericDrawables (Phong/Flat) and PBRDrawables was promoted to the base Drawable class. This includes management for lights, shader keys, and skin data and handling, in order to reduce needless code duplication and also as pre-requisite work for the upcoming PBR Skin rendering support.
• The PBR shaders were originally implemented to perform calculations in model space, while the Phong and Flat shaders work in Camera space (ModelView transform). This caused the PBR shader to perform many redundant matrix multiplications unnecessarily. This distinction has been removed, and now PBR operates in Camera space, just like Phong and Flat shaders. This change is temporarily reverted until a reasonable solution to calculating IBL properly in camera space can be derived.
• The PBR shaders were originally able to handle double-sided textures but this was disabled due to an issue with rendering artifacts being produced at edges. Since the PBR rewrite, this issue seems to have been addressed, and so this PR reactivates the ability to disable backface culling for double-sided textures.

How Has This Been Tested

All c++ and python tests pass locally

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.

[0mdc]

LGTM! Left some very minor comments.

[0mdc]

👍

[0mdc]

As discussed, there is a transform issue when projecting the environment map.

For reference, see the mirror in this video.

pbr_test-2023-10-02_11.50.20.mp4

[jturner65]

As discussed, there is a transform issue when projecting the environment map.

For reference, see the mirror in this video.
pbr_test-2023-10-02_11.50.20.mp4

I'm reverting the changes to the PBR shader using camera space vs world space until this issue with IBl being calculated in camera space can be addressed properly.

[0mdc]

LGTM! The issue is fixed with the latest iteration.