need a transparent bg for my particles
 

Hi,

I have created a scene with point particles (instanced with geometry) and I hardware render them with full image resolution, as tiff, and tried targa, alpha off, etc. The particles show up very nicely but then when I composite the sequence in my scene, with a blue background, the particle seq comes in with a black bg. I thought it would be trasparent.

I have a pic of what it looks like but I had to convert it from tif to jpg to post here.



The background option is set to black. I dont know what else to do.....Any suggestions?

Have u tried alpha on ?

Yes, Tried that and then no particles even show up at all.

In your comp package just use a luma key. I'm not sure why the particles aren't rendering with an alpha, but from the pic above I think you can easily get away with a lumanance key, or changing your layer mode to screen or add or something to that effect.

You "CAN" render your sequence in Software to get an easier alpha, but in your case I believe the reason you are not seeing your particle-instances when alpha is ON, is because that flag does NOT mean particle alpha.

It is a GEOMETRY mask/alpha, meaning, say you are emitting particles (instanced or not) FROM geometry to make them appear to make a shape, the "alpha on" flag will OCCLUDE the geometry from your particles, making things easier for you in post for those "around the world" effects.

So, if you are emitting your particles from geometry, you must remember that Maya wants to take your geometry into account as well when it comes to the final render.

So, if you ARE emitting your particles from geometry, make sure that in the geometry's "shape" node that you have "primary visibility" TURNED OFF.

This is DIFFERENT that just turning its' visibility off in the channel box, so remember that too:)

If none of that helps, I've got another idea so just lemme know:)