Cxbx-reloaded: Emulate Xbox Fixed Function using a HLSL vertex shader

[PatrickvL]

Currently, Cxbx 'emulates' the Xbox Fixed-function vertex shader via the host Direct3D 9 fixed function pipeline (via SetFVF).

This has a few down-sides :

• host might behave differently from Xbox (we don't know for sure)
• using host fixed-function blocks a port to newer Direct3D versions
• we have to treat FVF differently from programmable vertex shaders

(Note, that Xbox D3D internally uses one of three pre-defined vertex shader programs specifically for D3DFVF_XYZRHW - those we should treat as normal vertex shaders, but that's another issue.)

For this issue, implement the Xbox Fixed-function pipeline as a HLSL vertex shader.

This would allow us to remove all host fixed-function code (like how we forward Xbox SetLight to host, and many other things), and would result in accurate emulation of Xbox Fixed-function features.

[ObiKKa]

So, both PRs #1801 (replaced old vertex shader code with HLSL vertex shaders) and #1805 (more fixes), that were in the works between late November to late December 2019, hadn't covered the above post regarding Xbox fixed function features?

[RadWolfie]

HLSL's fixed function is actively being work on by one of the developer. 🙂

[PatrickvL]

Status : NZJenkins is working on this issue, here : https://github.com/NZJenkins/Cxbx-Reloaded/commits/fixedfunc

[PatrickvL]

Perhaps while working on this, this texture-coordinate scaling issue can be addressed as well : https://github.com/Cxbx-Reloaded/Cxbx-Reloaded/issues/1788#issuecomment-556991881