Using Blender Eevee and HDRI lighting for rendering ShapeNet

[lalalune]

We've modified the input scripts and are starting on our journey of training the models:
https://github.com/webaverse/GET3D/blob/master/render_shapenet_data/render_shapenet.py

We got much faster and more game-like generation results by switching to Eevee renderer and going to HDRI. Eevee renders 24-frame multiview in ~3-4 seconds per model, and it can crank through an entire average-sized shape category set in about an hour or two.

Also, because it's a realtime-style rasterizing renderer, it's pixel perfect and not subject to noise. To compensate for a lack of dimension we've lit the scene with a studio HDRI and applied an ambient occlusion post processing effect.

So, questions for the team:

1. do you see any issues with this, is there a requirement for the realistic renderer?
2. would you accept a pull request for this? we will need to modify our code since we are also doing some transformation to normalize the ShapeNet V2 dataset, but I could make a PR to switch between eevee and cycles.

[SteveJunGao]

Hi @lalalune,

Re 1: We hope to render the image as realistic as possible, as the 3D assets are learned from the 2D images, this is the reason why we have ray tracing to create the realistic image.

Re 2: Rasterizing the image is great in speed, but this could sacrifice realism. This part is not the main focus of this paper, and the rendering only needs to run once, then we can reuse it. Unfortunately, it's hard for me to accept this pull request, as it could make this repo giant and I hope to keep it simple.

If you have any other pull requests on improving the model or training aspect, I'm more than happier to take it!

[lalalune]

Well, for those of us making games, Eevee is actually a very realistic approximation of the renderer we're using, and with HDRI lighting actually looks better than Cycles and without the noise issues. I applied a studio HDRI and ambient occlusion as well as a little color correction to get good edge detail.

My concern is if there is any reason to expect reduced quality, but as we've been digging through it I suspect this is a good path and we just need to show results.

Attaching a couple of Eevee renders for reference

[SteveJunGao]

This looks awesome! Can you provide MR and I can evaluate how big changes we need to do to make it faster.

[lalalune]

I have added details in this pr: #17