Reflection Occlusion

[Christoph_H]

Hi,

is there a possibility to put on a reflection mask?

I can set a layer in the render passes that only render a ground reflection.
Can I put on a greyscale mask for that? 

thanks.

Edited July 12, 2018 by Christoph_H

[davpe]

what if you plug your mask into a reflection color parameter? that should do the job, right?

[Christoph_H]

sounds good. But I can't manage it somehow. Does that work for you?

 

Thats a similar solution but in my opinion a little bit clumsy.
An alternative way would be good.

 

Edited July 12, 2018 by Christoph_H

[davpe]

don't see how that topic is similar but masking works just fine. 

 

[Christoph_H]

Maybe that was confusing.
But that's what I mean: A reflection in color and a mask.

 

[davpe]

oh you mean that... well that's unfortunately not built into mantra by default. you would have to do some shader writing to get that. agree it'd come handy sometimes. i just render separate pass if i need that. not a huge hassle.

[Christoph_H]

thanks for the info. 

There's another thing I'm interested in: How can I render a pass alone? So without a beauty pass?

Edited July 12, 2018 by Christoph_H

[davpe]

you can use style sheets to make material overrides for that standalone pass. all objects visible for reflection mask will have white constant material and the receiving object will keep the "beauty" material but with everything except reflections disabled. lights would be off. for convenience you can merge those two rops and render them in sequence so you don't have to run them separately. this works best if you want to isolate ground reflections or so. not if objects are reflecting each other, obviously. if i have some time later i can post you an example file if you care.

cheers.

Edited July 12, 2018 by davpe

[davpe]

here you go the hip file

 

refl_mask_pass.hiplc

[Christoph_H]

interesting. I didn't know the stylesheets yet. Gives you a lot of options. Thank you.

But basically you can't switch off the beauty pass? At least that is possible with other programs.

[davpe]

yeah style sheets are really great for building passes and working with many objects/instances.

not sure what do you mean by "switch off beauty pass"...

[Christoph_H]

For example, I was rendering a scene. But I forgot the Depth layer or a simple mask. Then I don't want to render the beauty pass again. It'll take longer than that.

[davpe]

well you can make your "beauty pass" whatever you want. you can make depth your "beauty pass" if you wish. in the example i posted, just the mask was the beauty pass because real "beauty pass" shaders were overriden in a style sheet and never evaluated in that particular render.

it all depends how you design your materials. if you have some complex shading with aovs as a part of the same shader tree, then you have to execute the entire shader to get the aovs, but you get all that in one go.

if you forgot about some passes before rendering your main pass, nothing stops you from building those additional shader bits and pieces aside in a separate shader, use style sheets to build overrides and render just that very quickly. then you can easily merge those new shaders with the original one so you don't have to keep rendering those little forgotten bits as a separate sequence for future versions. 

hope this explanation makes sense

 

edit: maybe you will understand better if i say that you can't get just aovs without rendering the main pass, but you can make your main pass empty (or put anything else you want there with use of style sheets), but still get you aovs. so you don't ever have to waste time on rendering something you don't need.

Edited July 13, 2018 by davpe

[Christoph_H]

yes, it makes sense.

thanks.