Author Topic: VDB's not holding out in some AOV's  (Read 5977 times)

2020-03-10, 04:33:21

Njen

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It seems that some AOV's can not be used properly when a VDB grid object is in the scene. If there is pixel coverage of a VDB object, I would expect that coverage to hold out what ever data is behind it. As it is currently, I can not use a number of AOV's in comp because it is not being evaluated in those AOV's.

For example, I can't use an RGB mask to isolate other objects behind the VDB grid. Other AOV's I would expect the VDB grid to hold out is in source elements and texmap elements. There are more as well, though I'm not sure how they would be rendered correctly (zdepth, UVW, position, etc.).

In the attached example, there is a VDB grid of rocket smoke in the middle of the image in the beauty pass, but there is no evidence of it in the attached AOV's.
« Last Edit: 2020-03-11, 04:42:22 by Njen »

2020-03-10, 05:31:38
Reply #1

Njen

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What makes it even more tricky/annoying is that because of the bug where if you have a visible VDB grid in the scene when 'Render selected' is set to 'Include/exclude list' then the list is completely ignored. I can't generate an alpha of the VDB grid with all of the scene lighting and materials affecting it in the RGB channels at the same time, and have the scene objects hold it out (objects can be in front, behind and inside the VDB grid at the same time).

I currently have to render a second pass where I apply a black material to all scene objects and make the VDB grid render with a constant white colour, then shuffle that into the alpha channel of the VDB beauty render in comp.

2020-03-10, 17:44:42
Reply #2

maru

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Thanks for reporting. As usual, we will look into this ASAP.
Marcin Miodek | chaos-corona.com
3D Support Team Lead - Corona | contact us

2020-03-11, 16:58:09
Reply #3

maru

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@Njen can you please check my notes below and let me know if they correctly describe what you are reporting?

1) Some (all?) render elements cannot be used properly when volume grids are used in the scene - e.g. the grid is not visible in a render element.

2) Volume Grids do not work as expected with the "render selected" feature - the whole bounding box of the VDB is considered, instead of just the actual visible part of the volume.

Generally, it seems that all issues you described come down to inability to render a Corona Volume Grid as a mask.
If it was possible, you could render the grid as a mask and use it to cut holes in other masks (insert the grid as black color) or cover objects behind it (insert it as white color).
Marcin Miodek | chaos-corona.com
3D Support Team Lead - Corona | contact us

2020-03-12, 08:42:33
Reply #4

Njen

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Hey maru, yup, both points are correct.

Also your twist on carving out a fake hold out by using a pure black colour is a good idea for the time being. Thanks!

2020-03-12, 17:40:36
Reply #5

maru

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Thanks for confirming.

Logged:
1) (Internal ID=477533402)
2) (Internal ID=477530807)
Marcin Miodek | chaos-corona.com
3D Support Team Lead - Corona | contact us

2020-03-27, 11:53:45
Reply #6

maru

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Started this thread to understand the issues and use cases better: https://forum.corona-renderer.com/index.php?topic=28378.0
Marcin Miodek | chaos-corona.com
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