Alpha mask Tweet

[kazinger]

How do I mask off parts of my mesh showing the background?
I have been working on this all morning.Im doing a animated helmet like in the Stargate movie.
Is that enough info? It is a basic question.
Thanks

[kavorka]

not exactly sure what you are doing.

Pics?

If I wanted to create masks, I would probably create them in my host 3D app.

You can also change your Kernel to info channel and use material ID. You can then use that to mask things out. But I have found much better results creating alphas in my 3d App (Blender).

Also, if it is just the helmet, nothing else, just turn alpha channel on in your kernel.

[kazinger]

A object as a mask to mask another object.
Its a animation with video sequence background . Video of putting on the head a tracked object( headphones with with dots). I use a head model for the mask . I put the helmet model on the head model and the head model masks out the parts of the helmet showing background. So you do not see the inside part of the helmet that is supposed to be on the other side of the head. So I need the moving mask. I need to do this in the Blender exporter for now.
I am still learning what kernel is. I have clicked alpha channel and keep environment. I have been through the wiki on this.
Thanks

[kavorka]

alpha channel wont help you here, it only puts an alpha for areas where nothing exists. You use this to do things like put a sky in post, etc.

In Blender, you can do this fairly simply.
you will need to have the objects you want on a separate layer. Then the objects you want to form your mas on another layer. In the render tab, go to layers and put the objects to use as masks in the mask layers.

Then I think all you have to do is go to the node editor and plug the alpha channel from your render layer into your composite node.

render the image sequence out in Blender and use that as an alpha layer in your video editing software.

I may have missed something, so if I did, just google it

[kazinger]

That will work.
I did this project before and it is difficult to see mistakes and many adjustments needs to be made to the mesh mask. I was hoping for something like the mask material in BI or the holdout in cycles.
Thanks Ill do that.

[TBFX]

You can turn any diffuse material into a mask material by checking the Matte attribute in the materials settings, this may be what you are looking for.

T.

[kazinger]

That is what I was looking for. You think I would have clicked that by now just out of curiosity. I did not see it in the manual but I was looking fast. I have a little trouble with shadows but if I use a plane and flip the normals it seems to work. A head mesh seems to cast on itself.

[TBFX]

A head mesh seems to cast on itself.

Yeah, it is designed as a shadow catcher so isn't quite a black hole material but you can usually get it to work for you.

T.