Face mode light linking using SG node isnt working in MtoMR

[mythravarun]

Am getting a strange issue with light linking in maya to MR.

If an object has multiple shader assignments in component mode, and if lights are linked using shading group nodes of those shaders, maya software renderer renders considering 'SG to light ' link but MR renderer renders with all lights illuminating all faces without considering 'SG to light' links.

Is this normal ?

Does this have any workoround or am I missing something ?

But its very bad that its working in maya software but not in MR, which leaves with a compulsion that few passes have to be rendered in software renderer and also contribution maps & associate pass methods cant be completly utilised in true sence.

[steve]

Hi,

the light linking as supported by mental ray for Maya is working on light-object relations, implementing the suggested and most common Maya workflow for make/break light links between lights and objects. Linking lights to sub-components of objects is not supported in this workflow. A workaround would be to split the object into sub-objects of the components you would like to use for light linking. However, light linking via shading group is supported by mental ray for Maya, by linking all objects contained in that shading group at once.

In general, per-face light linking is fully supported in mental ray. Actually, it is kind of the traditional way of linking lights per shader rather than per object. Some mental ray shaders still allow to link this way, although the workflow is less convenient.

Hope this helps. Best, Steve.

[mythravarun]

I couldnt understand your work around solution. So I thought its better to go with an example. CHeck the image for the example. Am using maya 2013 64 bit.

U can see that after connecting SG node to light, only faces that are linked to this SG node are only getting lit in Maya software render but not in MR.

Pls suggest any work around without splitting the geo based on shader assignment.

Thanks.