Buffer_writer - surface shader for rendering object with different shader for one pass. For example you need to render your object with lambert and also you need to render to different files Z, occlusion, reflection and etc. for future compose.
Supported 1 channel for rendering and 8 channels for write different buffers (files). Mental Ray 3.3 and early version has limit to 8 user frame buffers. In future releases this limit is reduced.
Buffer_writer visualize only first shader (render slot). Other shaders output to it own buffers and latter may be saved to different files.
Warning! This shader work only with mental ray stand alone. For rendering with mental ray stand alone from Maya GUI you may write simple mel script or take advantage of my mel script Render with Mental Ray Stand Alone.
Shader assigned as common surface shader. It have nine input color slots, only first slot(render) is visualize, other slots output to it own buffers.
For take advantage of this frame buffers you must declare it.
For example like this:
frame buffer 0 "+rgba"
frame buffer 1 "+rgba_fp"
frame buffer 2 "rgb"
For make it in Maya you must create custom text with this declaration on Render Globals/Custom Entities/Custom Scene/Custom Options Text with Append Mode.
For write result from custom frame buffers to files you need to create custom text on camera with Replace Mode and put followed text to it. (this is only example)
output "+rgba" "iff" "c:/output_render.iff"
output "fb0" "tif" "c:/output0.tif"
output "fb1" "tif" "c:/output1.tif"
output "fb2" "bmp" "c:/output2.bmp"
As a result we have several images of scane.
Warning! If you use May 6 and later don't use frame buffer 0 because Alias already use it for glow.
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If you find any bugs or you have any suggestions please mail me to firstname.lastname@example.org