Next,I will show you another cheap way of computing occlusion using mental ray and final gather on the normal mapped low poly version (it will not look the same as the ambient maps computed from the high version but will be a lot faster).

Lets say this is the final low poly with normal map (i will exemplify on the boot only but you can do the same for the entire character at once).

make a big plane and place it under your model

ake sure that the environment background color for perspective camera is white ( this way when final gather will be used and the rays will not intersect any geometry then the returned color will be wihte )

et the renderer to mental ray , make sure that you will check export maya derivatives

make sure in the Render Settings-> Common tab ->Render Options you will have the Enable Default Light option unchecked , its checked by default ( this will assure that maya will not create a default light and pass it to mental ray if you have none in the scene)and delete or hide all the lights in the scenes ( if any )

ADVERTISE

make sure to enable Final Gathering ( usually i set the Quality Preset in the mental ray tab to Production and then enable FG and increase the accuracy to 1000-1500 and leave the other options to default )

assign a new lambert to the low poly geo and set its color to full white and change the diffuse to 1 ( also change the same options for the default lambert or assign a new lambert to the ground plane and set its color to full white and diffuse to 1 )

select the material assigned to the low poly geo and assign/connect the normal map texture into the bump channel make sure you will use the bump as tangent space normals

before baking you can make a test render with mental ray and if all was done properly you should have a similar result