When drawing patches in Matlab, both faces are always drawn and with the same color. But when rotating the camera, I need that all the back faces do not be drawn. Any help would be appreciated.
No Lixiang. I mean that when simple polygons in 3D are drawn (using patch command for example), and you orbit the camera, both sides of the polygons are drawn with the same color. I need that only front-faced polygon be drawn on the screen (see this image as an example)
http://glasnost.itcarlow.ie/~powerk/GeneralGraphicsNotes/HSR/hsr_images/culledfaces.png
I see, Agustin. You can filter the data of the back face and then redraw the patch. Here I give you a simple example assumed that the plane slicing the front face and the back face is x=0.
Thanks Lixiang. Your solution is right, but the problem is that the plane slicing front and back faces is not constant. It depends on the camera position, so I would need to capture mouse movement (using a callback I suppose) and compute the new plane in every movement.
You can refer to Camera Graphics Terminology. I am not sure that you use camorbit function or campan function. The normal of the slicing plane is determined by the camera position and the camera target.
http://cn.mathworks.com/help/matlab/visualize/defining-scenes-with-camera-graphics.html
You should definitely play with the camera:
1) get the direction of the camera as the vector pointing from the current camera position get(gca,'CameraPosition') to the camera target get(gca,'CameraTarget); also, get(gca,'CameraUpVector')
2) create an orthonormal frame based on the viewing direction (the unitary vector CameraUpVector is the Z versor)
3) get a representation of the vertices and of the vertex normals of your patch in the new orthonormal frame
4) the backfire are those with negative Z normals face
You can implement this as a callback on mouse click/camera position.
Thank you all. With your help, I have achieved what I wanted. The steps have been:
Final example is attached.
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