Chaos Corona for 3ds Max > [Max] I need help!

Grainy image from Corona Sun

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cor:
Happy New Year everyone!

To make it easy to understand I recorded this short video (https://youtu.be/gF8eJ5H_HnE) of what is happening. Basically, we have an interior scene with some sunlight casting into the space. When we play with the light mixer in some combination we see grainy areas right where the sunlight is casted. What are we doing wrong or what setting are we missing. The denoising is helping a bit but it seems unusual that this graininess is showing up only at the sun lit areas?

romullus:
Hi,

This is expected behaviour. Lightmix is not designed to support extreme changes in light intensity. You can read more about it here (particularly "what are the limitations?" section): https://support.chaos.com/hc/en-us/articles/4528606952849-How-to-use-interactive-LightMix-in-Corona-for-3ds-Max-

TomG:
Corona is adaptive in terms of how it samples lights, giving priority to lights that have the most impact on a particular area. This means the sun takes priority, being the brightest, so other lights in that area where the sunlight land get less processing/attention. This means if you remove the sunlight, you will find the area noisy underneath because the rest of the lights weren't given as high a priority.

If you intend to use LightMix to truly control the end result, it's often best to make all lights a similar or identical intensity (including the sun), and set them to white, to give maximum control in the LightMix result.

cor:
Wow, thank you so much for this information! We were pulling out our hair for weeks before we figured to reach out for help. We will run a test and set all lights to the same white intensity and see what happens when we change the intensity and color in the LightMix. Have a fabulous week!

TomG:
Hope the test goes well! To avoid further frustration, remember that there are still limits on what you can do even with all lights the same color and intensity; changing things by too much (either brighter or dimmer) can still result in noise and so need more time/passes/stronger denoising. Exact results are scene dependent, but LightMix does have its limits (once you get into things like making something brighter by a factor of 10 or more, as a very very rough guideline!) It should give you the widest range of changes you can make though, if you set the scene up that way.

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