Matte/Alpha rendering

[thebrettwalter]

Hi, 

 

For a school project I have made a FLIP sim that enters the scene when a door opens. The project has been 3Dcamera tracked, matchmoved and model-built to sit in the shot nicely. I am wondering what the pathway would be to render only the visible sim once the door has opened to let the fluid enter the scene.

 

Would there be a material I can put on the door which will act as an alpha that I can use the original plate and as the door opens it is only the exposed sim that renders?

I don't know how to set this up, haven't done many complex renders at all.

 

I hope someone can help or at least point me in the right direction.

 

Because my working file has a lot of imported objects I have just uploaded a still frame, hope that's okay

 

[anim]

go to your Mantra node, Objects tab

by default there is * in Candidate objects, that means mantra will render all visible objects, however it's much safer to specify which objects to render no matter whether the display flag is on or not

so to begin, clear out * from Candidate objects

then in Force objects pick your fluid object you want to render

and in Forced Matte pick all the objects that you want to serve as matte/holdout, so your doors and walls

you can as well use constant material with cameramapped backplate on your doors and walls, that material will be still reflected/refracted in your fluid, but still matting it for primary rays

[thebrettwalter]

go to your Mantra node, Objects tab

by default there is * in Candidate objects, that means mantra will render all visible objects, however it's much safer to specify which objects to render no matter whether the display flag is on or not

so to begin, clear out * from Candidate objects

then in Force objects pick your fluid object you want to render

and in Forced Matte pick all the objects that you want to serve as matte/holdout, so your doors and walls

you can as well use constant material with cameramapped backplate on your doors and walls, that material will be still reflected/refracted in your fluid, but still matting it for primary rays

Thanks heaps!!!!