here is a simple test scene which shows four different sources of noise:
- noise in the reflection of the MIA Material
- noise in the shadows of objects
- noise in the general diffuse (when using mental ray's "use light shape" option)
- stepping and pixelation edges of object or in high contrast areas
to fix these issues you have to increase samples on each of these setting, knowing which samples to increase can help you resolve you issue faster.
for noise in the reflection you need to up the glossy samples in the reflection tab of the mental ray material, the less glossy it is the more samples you need to blur the reflection. 32 is often a good setting but if the reflections are very blurred you may need to go much higher than this. Going up exponentially is helpful (eg. 16, 32, 64, 128, 256)
noise in the shadows is normally due to ray trace shadows being on and the shadow rays not being increased. area lights need to have more than 1 ray to be smooth, upping that to 12 seems to smooth them out nicely.
the general diffuse noise is caused by the area lights high sample settings, increasing this to something like 16 can help smooth things out. The low sample setting is not often used, I believe it is called upon when the lights rays pass though an object or the reflection is seen in a reflection. If you notice grain in the shadows reflection you can try playing with that and seeing if it fixes it.
lastly edge noise can be due to the render sampling of the image, in the quality tab of mental ray's render options you'll find the raytrace/scanline quality, changing the max sample level to 2 and the contrast to .08 does the trick for me. Turning the max sample past 2 drastically increases render time so be careful.
hope this was helpful. This (along with most of this blog) is kind of a note to myself in case I leave mental ray for a while and come back to it later.
hope this was helpful. This (along with most of this blog) is kind of a note to myself in case I leave mental ray for a while and come back to it later.
