Sometimes we can get sploches and it could be really difficult detect the origin of this problem.

If you have glass materials in your scene, splotches like that:

could be caused by glass material without “affect shadows” enabled. If you active it this is the result:

Enabling this option you let direct light passing through the glass. For example if you have a direct light like sun, this option let sun rays coming in the interior.

In this case, this option disabled doesn’t stop the V-Ray Light rays but produce a lot of noise and increase a lot the render time:

• affect shadows – disabled: 133 secs with noise
• affect shadows – enabled: 39 secs without noise

If you want to test the differences DOWNLOAD THIS SCENE SAMPLE