invisible shader that will accept shadows
 

I was wondering how to create a shader that will not render in mental ray, but can accept shadows, basically I want an object to drop a shadow on a transparent plane..that I can then use to composite later?
thanks

i guess you are using raytrace shadows? ...if you want to take out an alpha assign a surface shader with a black matte opacity.

i think i already tried that? are you talking about the default surface shader node? just apply that, sorry can you elaborate im still learning

create a surface shader in the hypershade and then in the attributes of the shader is "matte opacity" drag it to black. this will render the object as black with no alpha channel. which is basically a silhouette. your shadows should have an alpha so you can comp them, so that should be that... i guess!

i think this is basically what you are trying, i have a shake script in this thread if it helps -> http://forum.simplymaya.com/showthre...threadid=31769

Yes your looks GREAT! thats is what I am trying to do, I am testing out this motion tracking software and I want my cereal box to "appear" that is it sitting on the tile...so I need a way to fake a shadow or something...I tried what you said and this is what I got??? i must be doing something wrong
http://i179.photobucket.com/albums/w...Picture1-1.png

have you matched the lighting? it looks a little dark on the front of the box compared to the special k and diet coke boxes.

also... they are not casting shadows, so why do you want yours to? an occlusion might be enough.

i would also switch to depth map shadows. they are much faster to render out. cos you render them in maya software.

Sorry that is a bad view, the special k actually has a lrarge shadow behind the flakes box, i have shadows turned on...but that black plane underneath is going to show nothing cause the shadows are black...Man I must be missing something I just want a transparent plane that does not render but is able to receive shadows??? I really appreciate the help

hypershade > use background > assign to plane :)

(make the plane bigger!)

Great almost there now how do i get rid of the super glossy reflection ?
http://i179.photobucket.com/albums/w...Picture3-1.png

think i got it just adjusted the reflectivity and specular...how do i get a better anchor shadow?(underneath)

you want an ambient occlusion...

umm not quite...

you need to render all these elements as different layers and composite them in a compositing package. its the only way to correctly match the noise, shadows, lighting, colour etc etc

no one just renders it all out in a one-er. :p

ok guess its a little more than i am capable of at this point ,,

just do an ambient occlusion and multiply it over in photoshop then :)

if it where for one frame yes that is a good idea...but this is motion tracking fom PfTrack

i really appreciate all your help regardless.