Noisy Render MultiMatteElement

[Garryclarke]

Hi

I recently needed to generate a multi matte pass from a file that I'd already rendered. Once I'd set up the MultiMatteElement I decided to switch off the Lights under Global Switches to save some render time. The MultiMatteElement rendered with really noisy edges.

After playing around with a few settings I found that if the lights are off (either in Global Switches or just individually switched off) and GI is enabled it will result in noisy renders. Switching off GI as well solved the problem

[johnnelsonvfx]

Are you changing the anti aliasing settings?

[svetlozar.draganov]

Proper sampling of MultiMatte elements requires to be calculated with RGB pass since V-Ray determines the sampling for the renderings based on the information in the RGB.
Turning of lights, making materials black and other similar actions will affect the sapling of the MultiMatte element. In order to get the samples back you may try increasing the Min Subdivs samples of the Image Sampler or to avoid using such extreme conditions where RGB is complete black.

[joconnell]

I find over riding with a vray light material and a default multisubtex does a good job to get around the lights off and materials black edges issue! might affect matte setups with glass though!