Author Topic: Corona Light Mtl becomes transparent in reflections when "Emit Light" unchecked  (Read 4314 times)

2014-08-22, 08:20:57

Polymax

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A7/A7.1/ DB06082014 CoronaConstant (CoronaLight without emmiting) is not reflected.
Conditions:
1. Directly reflect (not through glass(refractions objects)
2. Use Corona Sky in env.slot with default intensity
« Last Edit: 2015-01-19, 15:27:43 by maru »
Corona - the best rendering solution!

2014-08-22, 11:13:25
Reply #1

ecximer

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Why You don't use the self illuminated material?
sorry for my english

2014-10-01, 14:02:52
Reply #2

Coronaut

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I want to confirm this problem, same setup(as you would use LightMtl for backplate(constant)) only on glass with thin(no refraction) option as you would use in windows.
Solution for now(it sound simple but i needed days to figure this out... :D):
It does work(reflect) on normal glass with refraction.
Alpha 7.1

2014-10-01, 19:40:24
Reply #3

isnogud

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Long suffer the same problem.
A7, A7.1

2015-02-02, 23:15:48
Reply #4

Ondra

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I went over the code, and I found out that this is actually by design. Making the light shadow the background for reflections makes the result worse in the usual use cases with HDR enviro + jpeg backplate. Use the ray switcher material for more powerful solution
Rendering is magic.
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2015-02-03, 15:08:52
Reply #5

Ludvik Koutny

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The problem is that Keymaster said to use rayswitcher, but did not say how. That's not very helpful honestly. So here's what to do..

For background material do following:

- Create CoronaMTL, and set diffuse level to 0

- Enable self illumination and plug your background picture as self illumination color

- Plug this entire CoronaMTL material into directly visible, reflection and refraction slot of RayswitchMTL. Leave Global illumination slot empty

- Apply this CoronaRaySwitchMTL to your background geometry.

2015-02-05, 16:10:26
Reply #6

maru

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I always thought what Rawalanche said is the correct way of adding bg plates but there is still a small issue. If it's excluded from GI, it won't generate caustics. There should be some easy, dedicated way of adding bg plates.

2015-02-06, 09:56:20
Reply #7

Ludvik Koutny

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I always thought what Rawalanche said is the correct way of adding bg plates but there is still a small issue. If it's excluded from GI, it won't generate caustics. There should be some easy, dedicated way of adding bg plates.

Of course it should not generate caustics! The workflow is meant when you have finished your scene, and you are satisfied with everything lighting-wise. So now you just want to add some city or field behind the window while trying to alter lighting of your scene as little as possible, and trying to not affect scene performance in any way either but still want to get it visible in reflections and refractions, which would not happen if you comped the background in photoshop. That's the entire point. LightMTL with emit light disabled was supposed to do the exact same thing! Caustics are secondary light transport, so if you want that, then you simply use the material without that rayswitcher. Or use LightMTL with emit light enabled. But both of these actions will both change the lighting in your scene, and slow rendering down.

Most of the times, clients in Archviz want scene just the exact same way it is, but with different background behind windows. When i did that, i then faced the problem that BG was not visible in reflections, or refractions of object that were right in the middle between camera and windows. So it looked a bit odd when it was photoshopped. So i adopted the workflow of adding cards, that are visible only directly, in reflections, and in refractions, but not casting shadows, nor GI, not anything else that would change lighting or slow rendering down.

Also caustics are secondary raytracing effect, as is GI, so it's not separable, if you had it affecting caustics, then you would have it affecting GI as well, therefore it would be no different than using material without rayswitcher in the first place.
« Last Edit: 2015-02-06, 10:00:18 by Rawalanche »