Ramp_RGB in Standard Volume fails in IPR

[Will_Adams1]

Trying to add a color scatter ramp to a volume, I was finding that my volume was always rendering black in the IPR. After some exploring I found that the moment you drop a ramp node (rgb or float) in your shader network, even without even hooking it up to anything, the volume stops rendering correctly in the IPR. There will be a brief flash in the first pass of the render of the expected look but then quickly jumps to black. Rendering to picture viewer has the correct result. I'm currently using C4D R23.008 Build RB323902 and C4DtoA 3.2.1 (Arnold 6.1.0.1).

Basic volume shader renders correctly in both IPR and Picture Viewer:

Adding a ramp_rgb or ramp_float node even without connecting causes issues:

When connecting everything and rendering, Picture Viewer produces expected result:

Ramp node seems to work just fine with standard shader:

[Will_Adams1]

Update: Installed the latest C4D release R23.110 (Build RB330286) and i still have the same issue.

[Will_Adams1]

Loading other VDBs and creating a Volume from the C4D volume builder seems to not have any issues. This specific VDB is Smoke2 from https://www.openvdb.org/download/. I was just using this VDB as a test.

Not really an answer but at least I can move on with my life.

[peter.horvath6V6K3 · Accepted solution]

I couldn't reproduce it with C4DtoA 3.2.1, but the issue you described reminds me of a similar one which we fixed recently. Could you please check with the new 3.3.0 build if the issue is still there?

If so, could you try this workaround to see if it works? Go to Render Setting -> Diagnostics -> User options and type enable_fast_ipr off in the field.

[Will_Adams1]

Disabling fast ipr worked! Will install 3.3.0 and try again.

[Will_Adams1]

Confirmed this is fixed in 3.3.0.

[peter.horvath6V6K3]

Thanks for confirming!