Author Topic: Standard light and Translucency  (Read 288 times)

2019-01-09, 12:35:57

pdaniun

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Translucency effect is not consistent between Corona Light and Standard Light, despite creating similar brightness on the "inside" part of the material.
Translucency in the blue boxes material is set to 0,5, the left light is standard Omni Light with CoronaShadows and soft shadows enabled, right light is Corona Light Sphere. The Intensity is more or less matched in both lights, but the translucent effect is much more pronounced in the Corona Light.

2019-01-09, 14:44:14
Reply #1

maru

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I think that's because a Corona light has some specific area (surface), and an omni light is just a point, which also means that the Corona light is really closer to the walls of the translucent object. I would say this is expected.

2019-01-09, 15:33:48
Reply #2

pdaniun

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I was under the impression that translucency depends on the brightness of the polygon backface, not light proximity. As You can see in my example, the brightness on the inside is essentially the same.
Just to clarify, the Decay on the omni light is set to Inverse Square, starting at 5cm radius (that is the Pseudo area for calculating intensity decay for a point light)
The Corona sphere Light is set to 5cm radius. Intensity of both lights are the same, as one can see on the "walls" of the render.

So therefore, one would expect that the same intensity light hitting the inside of the box would produce the same effect on the outside, regardless of the distance from source.

2019-01-09, 17:26:14
Reply #3

maru

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Are you using UHD Cache here? Can you try with PT only?
Also, the inside is visibly brighter in the right side.


2019-02-26, 09:57:47
Reply #4

pdaniun

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Right. Winter break is over so let's get back to business.
Tested the scene with Path tracing, result is the same. In attachements are: screenshot of scene setup, properties for both lights and three examles of translucency in the box material.
With zero translucency the effect is identical for both lights.
With half translucency the corona light looks good, omni starts to look wrong.
With full translucency Corona Light works as expected (the "lit" side of material is on the outside) but Omni Light is totally wrong.

Corona version: 3
Full-speed, Non-debug, MaxSDK 2017
Build timestamp: Nov 21 2018 16:39:47