Refractive material + emissive light = insurmountable grain?

[chamferlain]

Hello! First post here, please let me know if there is a better place for it.

I have been struggling to remove the noise/grain from these lens renders! The lens itself is 8 elements. The ring lights are all translucent material with an emissive material behind them. I have tried just rendering with the front element only. I have turned global illumination off. These small region renders were run for 3-6 hours each. What can I do here? Will more time solve the problem, or will there always be little specks of color in a scene when dealing with emissive materials?

Thanks so much!

[bdesign]

Hey-

The first thing I would try is increasing the samples of the black lens housing material (for most material types, the samples parameter is accessed by clicking the little arrow to the left of the Roughness parameter; for some material types it is displayed outright). Also, if you happen to be using an older version of KeyShot, and the black material is the Paint type, this could be an issue. There was some bugginess previously with the Paint material type and Global Illumination. Hope this might help.

Eric

[richardfunnell]

Another suggestion would be to use a Point light diffuse or Area Light instead of the Emissive material; the emissive light (although quick) tends to be the grainiest.