View Full Version : Very tricky Question for mip_render_subset use...
04-17-2008, 05:31 PM
i have a case were i don't know what else i could try...see the image attached...this shows what i want to achieve using a mip_render_subset node...i can get my objects invisible, but when then the alpha in the subset also gets transparent...but i want it to be masked out while having the mask object invisible...
does anyone know how i can solve that?
thx a lot guys!!!
04-19-2008, 04:37 AM
You may need to do a matte pass. Technically if that sphere isn't in the subset it doesn't get shaded at all, so no alpha is produce for that foreground sphere.
04-19-2008, 03:54 PM
thx for your answer, but what u are saying is not true, cause objects that are not in a subset are getting the shader applied that is defined in the "other objects" slot....so i wanted to put transmat in it, but that did'nt work, cause the alpha also turned transparent...i tried some other tricks, but didn't get what i wanted...
i keep on trying...help still appreciated...a special matte pass is no option for me...does anyone know where to get the sourcecode of the mip_render_subset?
04-21-2008, 06:41 AM
I missed that part because it wasn't stated clearly.
I did go back and try to assign different shaders to the objects portion, however, it does not carry the alpha with it. (Possibly a bug but the shader is not supported at this time so Autodesk won't really help you with it.) Transmat will just pass the ray right through it anyway like it wasn't there.
Source code is also most likely proprietary.
However, my original comment seems to work. And here's why although you won't like the method since it defeats the purpose.
The Rasterizer still shades the sphere in the foreground even though it comes out black. I left the settings alone on the Subset (black for other objects) and still got an alpha for the hidden foreground sphere.
But you lose the speed gain with this since the Rasterizer still shades the hidden sphere. You can however drop the shading samples on the objects that are not beoing rendered so the render hit isn't extremely high or whole groups on a transform node (miShadingSamples).
04-21-2008, 07:35 PM
i think we missunderstood each other ;) I had a look at your pic and that is not what i am looking for too....
my foreground sphere must be transparent in rgb and black in the alpha...or was that what you intended with the rasterizer trick?
sorry for all the confusion...
04-21-2008, 10:13 PM
Ok now I think I understand you.
Subset is designed to render objects in frame while 'ignoring' others. Basically like a quick fix to rerender something. Objects that are hit are effectively ignored.
What you want is to render an entire object that may be behind something else without it being occluded.
That would be either render layers, or framebuffers. Framebuffers can achieve this trick (individual buffers can contain specific shaders on certain items). However, it is complex to setup and I haven't had the best luck with that yet, sometimes the object comes out reversed.
So honestly you'd be stuck with render layers.
04-21-2008, 10:13 PM
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