Author Topic: Need to render a mask that is behind glass  (Read 8046 times)

2018-07-27, 18:17:28

RobH2

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I have an object behind glass. I need to render a mask of it. The transparent material obscures the mask and if I render the mask with the glass turned off, the mask is not in the correct location due to refraction.

How can it pull a mask from something behind glass while leaving the glass enabled?

2018-07-27, 18:45:03
Reply #1

Frood

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Currently you can't. Simply that. Vote for

"Refraction/Reflection working with masking render elements (CMasking_Mask,CTexmap, etc...)"

here:

https://forum.corona-renderer.com/index.php?topic=96.0

if you need it desperately.


Good Luck



Never underestimate the power of a well placed level one spell.

2018-07-27, 18:58:07
Reply #2

RobH2

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Good enough. I'll vote.

Well, we all think that everything we need is "desperate" don't we...lol...? I'll render the mask in VRay I guess. I think it can do it.

Thanks for the fast response.

2018-07-27, 23:38:43
Reply #3

iancamarillo

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or hide the glass and re render only masks. I dreaded this workflow but surprisingly was very fast for an animation I did

2018-07-31, 18:59:15
Reply #4

Frood

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You don't get a refractive mask doing so. Depending on the (glass) object you only get some approximation but usually just a wrong mask.


Good Luck



Never underestimate the power of a well placed level one spell.

2018-07-31, 19:16:11
Reply #5

iancamarillo

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yes sorry, I misread the initial post

2018-07-31, 20:18:15
Reply #6

pokoy

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Smartass alert here but can't you disable all lights, set the glass reflection to zero, set the object that you need a mask of to self illumination 1/white and render that? Not a direct solution but maybe a viable workaround.

2018-07-31, 20:48:05
Reply #7

Frood

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Interesting hack! Now we have shadowcatcher workaround for opacity masks and self illu for refraction - and a horrible workflow :) But for that one mask quickly needed, why not.


Good Luck




Never underestimate the power of a well placed level one spell.

2018-07-31, 21:06:22
Reply #8

pokoy

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Yeah it's not very elegant but will probably work, I've used this setup on a few occasions. Forgot to specify that you'd probably need to use a LightMtl because you need to make the object not emit any light.

If you need the mask for reflections too you need to keep reflections enabled for the glass material. 

2018-07-31, 21:59:32
Reply #9

iancamarillo

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2018-09-19, 19:28:10
Reply #10

actrask

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I just had to do a similar trick that pokoy used. Put a Rayswitcher on the object behind the glass and have only the 'refract override' set to a self illuminated RG or B color. This will stop the self-illum from kicking out any GI. Put a flat black material on everything except the glass and refracted object. I'd save a scene state before doing this.

Aside from all that, is it really that hard to implement this or is it just not a high priority?


« Last Edit: 2018-09-19, 20:02:20 by actrask »

2019-07-13, 15:56:48
Reply #11

julienbe

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Same problem for me here.
I'm working on a commercial with a fish in an aquarium. It is practically impossible to use the render elements for post-production because of the refraction of the aquarium glass.

JULIEN

2019-07-15, 19:02:49
Reply #12

actrask

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What if you set the aquarium glass object to "not visible to camera"?


2019-07-26, 16:45:45
Reply #14

actrask

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Wow, I never knew about that. Thank you!