Nieves Miranda avatar image
Nieves Miranda asked ·

How do you render transparent glass using Arnold in 3ds Max?

I'm currently having problems rendering transparent glass using Arnold in 3DS Max. Pre-render, the glass behaves fine; it's see through. However, after rendering, the glass reflects the background color and becomes opaque so that if I place a different background color behind my render during post-processing, it doesn't show through what is supposed to be transparent glass.

Please see the Arnold render below.The black part on the lower left side is supposed to be transparent glass

Back in Mental Ray, I had no problem rendering with glass since the outcome is how I needed it to be: the glass ends up being transparent and even if I insert a background color post-render, you can see the color behind the glass as you should. See the two Mental Ray renders I have below: the first one is the render with a transparent background with the second one is the one wherein I inserted a colored background during post-processing. Notice how the glass retains its transparent properties post-render.

Any help in the right direction will be greatly appreciated. Thank you!

arnold3ds maxmaxtoa
glass-2.png (704.0 KiB)
glass-1-trans.png (149.4 KiB)
glass-1-bg.png (137.1 KiB)
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Mads Drøschler avatar image
Mads Drøschler answered ·

2 things needs to be done.
I created a video and stole your subject title so if people search on this they will bump into the video automatically.

Link to video:

qweqwe.png (294.2 KiB)
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I did this tutorial! It's what I'm looking for. Thanks so much!

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Hi! So far, your tutorial has worked well. I did encounter a problem though:

I only used one glass material for this. I don't understand why the Alpha is the way it is. The way I understand it is it should all act the same but the glass in the lower areas are reflecting the background color of the viewport. How do I make them all fully transparent?

Thank youQ

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alpha.png (1001.2 KiB)
alpha-3.png (507.2 KiB)
alpha-2.png (62.4 KiB)

Have you tried Transmit AOVs?

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However, I noticed that the opaque part is actually the flooring which is weird since the Alpha mask for Shadow Matte material is on. I also applied Arnold Properties to it and turned off the opaque option in the properties. I posted this as a separate question on this forum and am still looking for an answer.

Problems like these make me miss the old Shadow/Matte/Reflection in Mental Ray. That was way easier to deal with. Honestly, this is my biggest gripe with Arnold's Shadow Matte so I'm hoping they release a legacy Shadow/Matte/Reflection option.

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