Chaos Corona for 3ds Max > [Max] Tutorials & Guides

Caustics

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maru:
Here are some basic examples of caustics in Corona:

-there are two kinds of caustics: caused by refraction and caused by reflection, of course they mix on some materials

Refractive caustics:

To get them to work, you need to check "caustics (slow)" in your glass material's settings:



Max sample intensity (MSI) has impact on refractive caustics:


Caustics (slow) - MSI = 20 (default)


Caustics (slow) - MSI = 0


Default MSI value (20) produces less noise but "cuts off" some of the most intensive light passing through the object.
Higher MSI values or 0 will produce more realistic but much more noisy results.

If you don't enable "caustics (slow)" in your glass material, you will get transparent shadows. MSI has virtually no impact on transparent shadows (?). This can be considered "fake caustics":


No caustics (transparent shadows) - MSI = 20 (default)


No caustics (transparent shadows) - MSI = 0


If you enable "thin (no refraction)" in your glass material, your glass won't change direction of light rays. It will behave like very thin material (for example light bulb, soap bubble, etc.):


Thin (no refraction) - MSI = 20 (default)


Thin (no refraction) - MSI = 0


You can also render caustics using experimental features like VCM or BIDIR but they will most likely produce unusable results as they do not support some features like absorption:


VCM


BIDIR


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Reflective caustics:

My metal material:



MSI also affects reflective caustics:


Reflective caustics - MSI = 20


Reflective caustics - MSI = 0


Reflective caustics also can be rendered using experimental engines:


VCM


BIDIR


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Whole album (with screenshots of some more settings): [link]

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Note: currently, rendering of caustics of acceptable quality is very slow and usually it is recommended to use transparent shadows. For caustics lighting the whole room - like refractive caustics on the bottom of the swimming pool or reflective caustics from the surface of the water on the walls of the room, you can use CoronaLight with a bitmap assigned in its "texmap" slot. Caustics should work with both CoronaLights, standard Max lights, HDRI environment or other light sources.

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Comments/contributions welcome. :]

Ludvik Koutny:
Quite useful, but i think it would be a bit more convenient to embed images, instead of just linking them :)

maru:

--- Quote from: Rawalanche on 2014-05-07, 17:07:31 ---Quite useful, but i think it would be a bit more convenient to embed images, instead of just linking them :)

--- End quote ---
I didn't want to insert huge images into text and I'm too lazy to look for a way to turn images into thumbnails on imgur. :P
Done. MANUALLY.

agentdark45:
Thanks for the informative post Maru!

Admins, are there any plans to upgrade the caustics engine in A6 / future versions? Would be great to get a hassle free caustics setup that slots right in with the default settings (that doesn't take a crazy amount of time to render / or affect GI time). For example a definitive setup for a swimming pool / body of water in a complexly lit scene.

Ludvik Koutny:

--- Quote from: agentdark45 on 2014-05-07, 17:24:07 ---Thanks for the informative post Maru!

Admins, are there any plans to upgrade the caustics engine in A6 / future versions? Would be great to get a hassle free caustics setup that slots right in with the default settings (that doesn't take a crazy amount of time to render / or affect GI time). For example a definitive setup for a swimming pool / body of water in a complexly lit scene.

--- End quote ---

I believe so...  but it's not that high on the priority list though. I've suggested some quick solutions in the past, that would work, but Keymaster wants to do it right.

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