Author Topic: Corona Material  (Read 3377 times)

2013-11-28, 15:01:26

Paul Jones

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Just an idea here, but what was initially one of the nicest workflows for materials has changed slightly, and in my opinion is a step backwards. It was great to have emission in the normal corona material, now we seem to have lost this but gained a corona light material. Is there any chance of moving it back, as in some material setups you want light emission from some parts and not others,  lava for example - which ok can be done with 2 materials and a blend but it's just not as nice a workflow imho.

Whilst we're on it can the emission have physical units please?


2013-11-28, 15:36:52
Reply #1

shadowman

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Are you bout latest build?
CoronaMtl -> Advanced options..?

2013-11-28, 16:03:18
Reply #2

Paul Jones

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if I read that correctly there is no light, just a self illum - and also no map slot

2013-11-28, 16:12:39
Reply #3

Paul Jones

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ok thanks for the heads up - there is the map slot in slate node view - I was looking at the white colour swatch in the parameter editor with no spinner, map slot etc.
After testing the self illumination does actually emit light, so why not rename it emission again as it's doing more than actually self illum

2013-11-28, 16:43:09
Reply #4

Ludvik Koutny

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ok thanks for the heads up - there is the map slot in slate node view - I was looking at the white colour swatch in the parameter editor with no spinner, map slot etc.
After testing the self illumination does actually emit light, so why not rename it emission again as it's doing more than actually self illum

It is not nearly that simple.

This is very fresh, and in final release, UI will be more polished. In CoronaMTL, there will be a warning message.

Basically, the reason this was done is that many people were irresponsible enough to make emitters with refraction, translucency, and stuff like that, and then they complained about slow rendertimes.

So now there are two types of light: Explicitly sampled, which is in CoronaLightMTL, and light that is not explicitly sampled, which is self illumination in CoronaMTL.

If you were to use self illumination as some key lighting source, it is going to suck. Use CoronaLightMTL...  that is intended for key lighting in your scene, for an actual emitters. Use self illumination where you actually want to self illuminate some large dim surfaces, or some small glowing features. For example if you had crowd of 10 000 animated creatures, and they all had little glowing veins on their bodies, if all the polygons on all the instances had to be explicitly sampled for direct lighting, it would be very inefficient.

Also, you would use self illumination for mattes, where you have bitmaps, that are actual luminance, not reflectance... meaning the lighting data is already baked in them... if you have large building with baked illumination, you do not need to explicitly sample it.
If there is another building next to it, and it receives indirect illumination from it, it is same, as if it had regular materials, and some light would shine on it, then you would not explicitly sample that neigbouring building either, it would be just regular GI bouncing, the building would not be considered emitter.

So, to wrap it up. Use CoronaLightMTL for any light sources that cause some key lighting in your scene...  and use Self-illumination in CoronaMTL for some small or very dim glowing features of materials, for mattes that need to cast light, etc... CoronaLightMTL is specifically optimized to be as an emitter, while Self-illumination is just getting picked up by GI. If you set max sample intensity to 0, and have both CoronaLightMTL and CoronaMTL emission set at same value, both will eventually converge to 100% same result. Yet, one or other will be faster, depending on the situation.

Right before Alpha V6 is released, once UI is in final state, i will create some tutorial specifically for this topic.