Thank you for your answer. In fact I did not try your approach, instead I tried two jit.gl.gridshape with matrix output 1 and send them to a jit.op... I tried different operators but i did not manage what I pretend. Let me be more clear:
I think this needs to be done with textures/color.
Send both shapes to a jit.gl.node @erase color 0.5 0.5 0.5 1.
Then gridshape @shape plane @color 1. 1. 1. 1. @ layer 0
Gridshape @ shape circle @ color 0. 0. 0. 1. @ layer 1
Apply all movement and rotation instructions to both gridshapes.
Missed the part with it being see through.
I wouldn't try to make the basic shape in max.
Create a circle and a cube, use the boolean modifier to cut out the square shape from the circle.
Export as dae model
import with jit.gl.model.
Well thats not so hard if you get a little creative.
The square shape can be defined as a few vertex points.
By using jit.gl.model @matrixoutput 1 to a jit.gl.mesh
Then only altering the vertex points of the square form (x,y vertexes only)
then you can change the square form.
Start experimenting !
I managed something with blend_modes... We can see the background color through the square inside the circle but if a place a videoplane behind the circle and the square I can't see the videoplane any longer :-/