Hello,

I m kind of new to GEM but im trying to do sth that should be easy...
I want to have a pix_film playing in the whole window on the background and mask it with a circle so only the part that is 'behind' the circle shows..

The circle should move in real-time in order to see other parts of the video.

Any suggestions?

Thanks

One of those "should be easy, but..." questions, I'll pitch in if I can dig up a working patch. You'll need to grasp [pix_snap], that much I know.

Hello nestor,

Thank you for your reply.

I played around with the [pix_snap] object and it seems to do the trick..
The way I managed to do it is the following:
1. I create a [gemwin] twice the size of the screen
2. In the invisible part of the screen i create a white rectangle with a black circle on it
3. In the visible area i create a [pix_film] object that plays the video
4. Using the [pix_snap] i put the 'snap' of the rectangle with circle on top of the video
5. [pix_alpha] makes the circle transparent and displays the video.

It still doesn't seem the right way to do it but its working..

Thanks

That sounds about right. Honestly, the pix_snap is the difficult part, the rest is just fiddling. As with most things in Pd, there's multiple ways to do it. You may want to mess with the [pix_texture] environment mode to fully mask (not just black) the video. There may also be a way to 'transpose' the greyscale value of the pix_snap raster to an alpha channel for your video, I can't quite recall how to do that, but it involves unpacking the color info for both.

hi everybody, some time ago i've made this super simple glsl mask for gem. it should work just out of the box and be kind of flexible. give a look, hope it helps

http://www.pdpatchrepo.info/hurleur/glslSimpleMask.zip