how to reduce a grain in render?

[kostache]

I have a problem with too grainy renders. Light sources are "linear" and "quad". Kernel - diffuse, specular level - 8. Motion blur is on. Max samples 3000. Does any method exist to get rid of this grains without paying a lot of time to render?

[juanjgon]

Small thin lights, like the linear lights, are prone to render more noise than big planar lights. Perhaps you could try to replace the linear lights with quad lights, with the biggest possible size.

-Juanjo

[kostache]

Thanks Juanjo!

I've increased a size of my lights more, than twice - not so much different result. But I've noticed, if I'm using one machine to render (app. 2.35m scene width), grain amount is much less, then if I used to render 6 machines in a row (17.2 m scene width). Do you have any other advices in this case?

[BorisGoreta]

You have to learn how to balance the lights in the scene. For this you have to activate clay rendering mode, set the kernel diffuse and spec depth to 1, set all light sampling rate to 0 plus any emmiting geometry sampling rate to 0. Now set the first light sampling rate to 1 and set the kernel to stop rendering at some 1000 samples. Then set the sampling rate of the second light to 1 and see if the noise from both lights are the same. Then the light sampling is balanced, if not, reduce or increase the sampling rate of the second light. Some light need very low sampling rates and some very high sampling lights in order to output the same noise levels into the image. Do this for all other lights and emitting geometry and then you got a balanced render which won't waste samples where it doesn't need to.

[kostache]

Thanks Boris! I'll try

[kostache]

You have to learn how to balance the lights in the scene. For this you have to activate clay rendering mode, set the kernel diffuse and spec depth to 1, set all light sampling rate to 0 plus any emmiting geometry sampling rate to 0. Now set the first light sampling rate to 1 and set the kernel to stop rendering at some 1000 samples. Then set the sampling rate of the second light to 1 and see if the noise from both lights are the same. Then the light sampling is balanced, if not, reduce or increase the sampling rate of the second light. Some light need very low sampling rates and some very high sampling lights in order to output the same noise levels into the image. Do this for all other lights and emitting geometry and then you got a balanced render which won't waste samples where it doesn't need to.

Hello Boris,
I've made a light balancing the way you told me, but I still have a number of questions. How to manage a very small emitter in case of sampling? keyboard lights, for instance, in comparison with lights in work area of machines. They do not produce any noise as such. I spent .001 of sampling rate for them (I case, that I've taken 1 sample for machines work area). And most important thing, that I anyway need about 6000 samples for render kernel to make noise free picture. But this is too much! Does any other way exist in Octane to reduce noise without paying so much time to render? Because the object, that lighted with environment map looks good even with 1000 samples!

[geo_n]

Are you doing interior or enclosed scene? There's very little way to reduce noise without more render time or render power with pathtracing bruteforce.

[kostache]

Yes, like in embedded sample. 6 machines in a row

[juanjgon]

What kernel are you using? ... perhaps you could reduce the ray depths to only 2 or 3 to see if this help with the noise. Sometimes a lot of light bounces only add more noise to the scene, and lighting can be good enough with only few bounces.

-Juanjo

[kostache]

Diffuse. 8 bounces for both specular and glossy depth. It's a good idea. I'll try try to reduce it and make a test