yopla

does anybody know how making a 3D mask with a kinect ?

mask-kinect

What is a 3D mask? You can use the depth texture from the kinect to cut out the color texture to some threshold, although the 2 camera positions aren't identical. You could even apply the values from the depth to a mesh shape's z-coordinate...

i want to draw an area with a free form (a sphere for exemple) in the 3D space of the kinect image, and use it as a mask

the thresold from depth texture only allow a plane (or a cube) wich is perpendiculare (with the method for extract a slice from Blair Neal)

the 2 methods for undistorting the Kinect depth map in Max/Jitter by Dieter Vandoren seems to be a good way,

but i wonder how put a 3d form inside, and use it as mask, in order to trig when something enter into the mask for exemple.

I'm hoping I understand you correctly here. Say you only want to draw stuff that enters a virtual sphere on stage (in front of the Kinect).

The Kinect gives you both color and depth, but from the depth you're able to get the object's (or pixel's) position. So you should apply the 3dmask to the depth buffer and calculate for each pixel whether it's inside your 3d mask. Then you could take the result (a single plane binary texture, 0 - outside, 1 - inside the 3dmask) and apply it as the alpha plane for the 3 plane color texture you already have.

Pseudocode for the alpha texture would be something like this, where x, y and z are scaled equally (i'd probably try to make it using jit.op first):

x^2 + y^2 + getDepth(x,y)^2 < sphere size^2 then 1 else 0

(note that a more complex shape as a mask makes things a lot more difficult)

Then you should apply the depth texture to the z-coordinate of your mesh. Make sure the mesh has a high enough dim to get some detail. Because your color texture now has alpha the parts outside the mask will not show. So you will now only show the are you were looking for (in space).

I hope i'm not trying to explain something that's already clear-cut to you and you're trying for something much more difficult, plz tell me if that's the case. Good luck!

I'm hoping I understand you correctly here. Say you only want to draw stuff that enters a virtual sphere on stage (in front of the Kinect). 

Pseudocode for the alpha texture would be something like this, where x, y and z are scaled equally (i'd probably try to make it using jit.op first):
for each x
   for each y
       x^2 + y^2 + getDepth(x,y)^2 < sphere size^2 then 1 else 0
(note that a more complex shape as a mask makes things a lot more difficult)

I hope i'm not trying to explain something that's already clear-cut to you and you're trying for something much more difficult, plz tell me if that's the case. Good luck!


mask kinect