Probably a really newbie question. I've been experimenting with Houdini off-and-on for about two weeks now.

I've got mantra_ipr set for 8-bit integer and Output Device as TIFF. Using Houdini 16.5. Rendered images look fine in Image Viewer, but objects in the image are missing when I view in other image viewers such as Apple Preview.

This question has appeared here (long ago!) and in other outside forums but those answers don't seem to apply.

I'm wondering if I'm missing an entry in the Export Components tab. I've experimented with the ‘Basic Components’ and ‘Common Components’ settings, but results are the same. I've been unable to find a description of the permitted values in the ‘Rendering’ section of the documentation.

Suggestions?

Thanks,
Tom

I think I solved at least part of the problem.

I was using a shader with ‘Glow Color’ to represent atoms and molecules. On some, I had turned on ‘Enable Emission’. This flag seems to stop objects from rendering in a standard TIFF with my current settings. So ‘emission’ makes stuff invisible??

Still has me wondering if there's something for the ‘Export Components’ of the mantra_ipr node that resolves this. I currently have ‘diffuse reflect coat refract volume sss’ in this list. I assume other entries are possible. Is there a ‘master list’ of valid entries for this parameter? I tried ‘glow’ and ‘emission’ with no results.

Thanks,
Tom

Does taking off tiff compression option make a difference?

Emission renders color without any alpha (A=0), as it is purely additive. So when when you blend it with a standard over, you get C = Ce + (1-0) * Cbg, where 0 is the emissive alpha. If there was an Alpha, it isn't emissive anymore - it'll block some of the color from behind it. So I suspect the other viewer was premultiplying color by alpha, and we all know how multiplying by zero works out

Turning off compression made no difference.

The alpha explanation makes sense, and raises a related question. I was noticing my images were always rendering with alpha. But short of installing some background geometry, I haven't found a way to turn off the alpha layer and/or force a default background color. Sometimes I just want an RGB, not an RGBA. Can that be done in Houdini or is that an external step?

Thanks,
Tom

Check you bit depth. Unless you change the default, you are probably rendering 32 bit color with alpha. Many viewers are 8 only and no alpha.