How do I create a Maya "use background" shader equivalent?

[iain_h]

Hi,

I have some hold-out geometry that I need to render as the background plate.

I have tried camera projecting the background plate onto the geometry but I get some small artefacts and when some of the vertices goe out of frame I get larger artefacts.

Any ideas?

As an aside, the OpenGL preview of the camera projected textures is sometimes way off. Is this to be expected?

Thanks.

[~nature~]

Hi,

I have some hold-out geometry that I need to render as the background plate.

I have tried camera projecting the background plate onto the geometry but I get some small artefacts and when some of the vertices goe out of frame I get larger artefacts.

Any ideas?

As an aside, the OpenGL preview of the camera projected textures is sometimes way off. Is this to be expected?

Thanks.

Actually, I have same question but here is the imperfect solution.

1. rendering out your expected elements like shadows or reflections via passes and do the compositing work in Compositing software or Houdini COPs.

2. if you want to preview it directly at the rendering time, you have to do some shader modification, you could connect the shadows color to the opacity output or color output, In the latter case, assuming you don't use PBR render.

Hope it helps.

Cheers.

[onkel_eilert]

You could put the shadow matte material on the holdout geometry and load in the backplate in the renderview background. The shadow matte adds the shadows to the alpha channel. Remember to turn off the alpha contribution on the shadow matte.

[iain_h]

Thanks for your help.