Author Topic: issues controlling reflection/refraction through glass  (Read 970 times)

2021-06-29, 10:02:44

simon@CT

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(The attached pdf seemed corrupted. I have added 3 jpgs instead).

I have finally given up trying to resolve this issue by myself. I am posting in the hope that someone can guide me towards the answer so that i don't have to render twice and fix in post :|
If i place a billboard behind my scene to cast reflections from the photo on my water, i can't project the image through the glass onto the water without embedding the image in the glass material.

I have attached a pdf which hopefully helps to explain the issue....

Page 1.
The basic setup in 3dsmax, with the object and material properties. Nothing too complex. Just basic glass materials and a corona Light material for the billboard. The checkboxes "visible to refractions" and "visible to reflections" do what they are supposed to do, but I can only assume that i am doing something wrong, or there is another checkbox somewhere.

Page 2.
The main image shows what happens when i check "reflections only'. It renders as you would expect... however it can't penetrate the glass, to project the image onto the waters surface. The background override (black) appears on the waters surface instead of the billboard image.
If i select the 'visible to refractions' it projects the image onto the water.... but now the image embeds itself IN the glass.

Page 3.
Shows the final image with the glass and water reflection appearing as you would expect. However to get this result, i have to render two passes to remove what i don't want. Annoying.

I would be most grateful for any suggestions.
« Last Edit: 2021-07-01, 02:18:28 by simon@CT »

2021-07-01, 07:40:17
Reply #1

junchien

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Try changing the glass refraction IOR1.6 to 1.001

2021-07-01, 07:53:43
Reply #2

simon@CT

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No luck. Doesn't matter if i make it 1.001 or 10. It still cuts out the billboard image.

Another workaround is the open the properties of the glass object and switch off 'visible to reflecttion/refraction'.... however when you import the image in aftereffects the alpha channel clips out the glass and therefore removes thereflection from the glass.

2021-07-01, 09:37:26
Reply #3

NicolasC

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Good morning,

Very weird indeed ! have you tried to uncheck Cast shadows property for the glass objects ?

EDIT: just seen you've already done so, sorry. No idea about solving this issue, but I'm very interested to know the fix !
Nicolas Caplat
CG supervisor / teacher / artist

2021-07-01, 09:39:17
Reply #4

simon@CT

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yep.  Either Corona is missing one checkbox.... or i just can't find it.