can't get background plate to render (Houdini 20)

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I put a Background Plate node before my Karma Render Settings node, no holdouts. The background plate appears in the viewport but not in renders. A assume it's supposed to? Is there any way to make this work?

Edited by gladstein - Nov. 11, 2023 11:44:40

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Screenshot 2023-11-11 083804.png (541.3 KB)

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You have to connect the second output of the backgroundplate node to the second input of the karmarender settings.
Edited by spinori - Nov. 12, 2023 06:08:04
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Thanks! I did try that, and it didn't seem to help. I've attached an updated pic and the .hiplc file.

Image Not Found
Edited by gladstein - Nov. 12, 2023 13:19:35

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Screenshot 2023-11-12 100526.png (76.0 KB)
BGplate.hiplc (731.8 KB)
BGplate.hiplc (731.8 KB)

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You need the geometry to project the background plate onto. Add a grid below your cube and set the background plate LOP's "primitives" parameter to point to the grid.
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Thanks! It didn't help. New .hiplc file attached.

The render result, with a touch of diffuse color from the Offscreen Color of the plate LOP:


The cube and grid:


Image Not Found
Image Not Found
Edited by gladstein - Nov. 13, 2023 13:20:35

Attachments:
result.png (77.2 KB)
cube_and_grid.png (130.0 KB)
BGplate.hiplc (834.7 KB)
Screenshot 2023-11-13 101918.png (102.5 KB)

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Hi. The background LOP assumes that the elements will be rendered separately and tweaked/composited in comp, hence why the slapcomp only happens in IPR for previewing. But if you wish to render out what you see in the viewport you can certainly do so: place "Render Settings Edit" node after "karmarendersettings" LOP, under Karma->Global->Image, change "Use Background" property to "On"
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Thanks so much! The Render Settings Edit was all it needed to work.
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