Mantra Holdout with Phantom not acting as expected

[mattak]

Hi everybody, thought I'd throw up a simple file to demo the problem,

In the context of rendering a flip sim mesh in mantra, with the env geometry as both holdout 'forced matte' and 'forced phantom' to have it still show up in reflections and refractions,

I have a situation where by adding the object as forced phantom, it cancels out force matte.

But as a work-around -  it seems if I duplicate that same env geometry, by copy&pasting the sop, and setting that new sop to be the phantom and not the original, mantra renders as expected.

Go figure...

 

Cheers,

Matt

 

01 Render with everything visible

02 forced phantom cancelling forced matte

03 both forced matte and forced phantom working after sop object duplication

phantomHoldoutTest_v001.hip

Edited April 3, 2018 by mattak
naming/description of images

[Skybar]

What if you only use Forced Matte?

[mattak]

Yeah your right. If I just use Forced matte and completely remove all phantom objects it renders the same, though I wouldn't necessarily expect it to, as only the spheres (waterGeom) are in Forced objects.

[anim]

you can read more about matte shading here: http://www.sidefx.com/docs/houdini/props/mantra.html#shading

Quote

When enabled, the object’s surface shader will be replaced with a matte shader for primary rays.

...

Secondary rays will still use the object’s assigned surface shader, allowing it to appear in reflections and indirect lighting even though it will not render directly.

...