From Ohm

Clip Planes

Iso surfaces are nested (onion shells). To see the inner shells it is often necessary to remove tissue that is occluding the inner parts. This is done via:

A clip plane removes the geometry on one side of the plane.

With OpenGL at least 6 independent clipping planes can be specified for the hardware pipeline.

A single OpenGL clip plane is defined by the plane equation

$ ax+by+cz+d = 0 $

When evaluating the above formula for points (x,y,z), results less or greater than zero indicate points on one or the other side of the plane.

For a plane with pivot point $\vec{p}$ and a normal $\vec{n}$ (pointing into the half space that is to be shown) the plane coefficients are:

The i-th OpenGL clip plane is specified via:

GLdouble equ[4];

equ[0]=a;
equ[1]=b;
equ[2]=c;
equ[3]=d;

glClipPlane(GL_CLIP_PLANE0+i,equ);
glEnable(GL_CLIP_PLANE0+i);

Retrieved from http://schorsch.efi.fh-nuernberg.de/roettger/index.php/MedicalVisualization/ClipPlanes

Page last modified on December 09, 2013, at 10:46 AM