Jonathan Mack


About Me

United States


Recent Forum Posts

Env light background alpha through glass / transmission Feb. 4, 2023, 9:59 p.m.

now you mau need to do another render of just refracted white dome to get the contribution that will act like Alpha for stmap, so that you can unpremultiply it to cleaner values for mapping
and then scale back down before adding the rest

if you put solid color in the blue channel of the st map, you can skip having to do a separate render.

Env light background alpha through glass / transmission Feb. 4, 2023, 12:23 a.m.

Why would you want that though? it's wrong and if you were to comp it like that, the dome light passing through the glass would be plussed onto the background.

If I switch to Arnold, with the same scene setup, I can enable "Transmit AOVs" on the Standard Surface glass shader + set the Dome Light Transmission Contribution to 0 and get the intuitive result seen here:

That result isn't intuitive to me. Why does the transparent part have fresnel gradations all over it? Where is the subject alpha in the internally reflected transmission? This result isn't useful for anything.

Nvidia rtx 4090 driver issues? Feb. 3, 2023, 1:03 p.m.


Sorry for my lack of knowledge, but where should we be entering the above line to try and fix the issue?


To permanently set it for just the user, add the line to your houdini.env file in the preferences folder.

To add it temporarily, it needs to be exported in the environment that launches Houdini.

On linux you would type export FOO=BARbefore launching, or add it to the script wrapper that your studio uses to launch Houdini.

On Windows, the Houdini Command line tools allows for setting env vars before launching Houdini with the set command.