I cannot render a sequence of frames of a pyro sim to disk with mantra. I can render to mplay fine. I can see the sim in render view fine. But when I try to render to disk, I just get empty pngs. I actually cannot render a single frame to disk, but I am attempting to render multiple frames. There is nothing in the scene but the pyro. If I put a mesh in the scene, it will render the mesh to a png to disk, but still will not render the pyro. There are no lights in my scene, because I am rendering a candle.

I don't understand why I can render the pyro to mplay fine but cannot just render that same image to disk.

I don't use mantra a whole lot, but redshift was having problems with this too and mantra could at least render something. This scene is very basic, so I'm sure it would not take an experienced user long to diagnose the problem.

I appreciate any help.

I think its because of the shader. Your Alpha channel is black and your pngs are premultiplied with the black alpha so you cant see anything. If you hit the “toggle transparency” button in the render view you can see that you render is also getting black in houdini.

kind regards
Jon

Hey Jon, thanks for pointing that out. Do you know how to fix this? I would want my alpha to be the heat channel essentially.

I didn´t test this but it should be possible to use the heat variable as an extra image plane in your rop.

Thanks jon. Just wanted to come back and say that Jon is correct and for anyone who runs into this your rendered files DO contain data, its just not visible in most image viewers. Well, at least for exr's the data is there (i switched to exrs and did not test with pngs). But to see it, you have to unpremultiply by the alpha channel. Still not sure the best way to do this. In after effects, you can use the eXtractor effect to switch the alpha channel to R, which worked for me since I was doing fire. Again, probably there is a better way, but this is what I ended up doing.