glClipPlane_gt.plugin

glClipPlane_gt from George Toledo on Vimeo.


I've made a plugin for Quartz Composer that calls on GL Clip Planes 0~5, which is the count of six that is typically supported by OpenGL.

This allows one to cull geometry in a scene by using eye coordinate values (the pitch, yaw, roll - sort of) to control 6 clipping planes. By default eye values (eg., patch defaults), no geometry gets culled.

Using the Clip Planes this way lends a little quirk - you really have to make sure you've disabled the GL Clip Planes via the ClipPlane Set input on the plugin, before you turn disable the patch or delete it, or the Clip Planes will hang around.

For some reason, managing the state of clip planes doesn't work exactly the same as some other related functions (like changing the projection mode, or enabling ortho, frustum, etc.). Doing the typical in this context (allowing the planes to change the entire scene instead of an object the patch implicitly renders...which works fine with patch deletion/disabling typically) results in clip planes not being active at all, so this uses a non-standard workaround to get functionality. Again, be mindful to disable the Clip Planes via ClipPlane Set before deleting or turning the plugin off, during a use session. If you forget, just place a new version on the editor, and toggle ClipPlane Set again.

This is a standard api QCPlugin.

In the vid clip above, I'm demonstrating culling the back geometry of the Heightfield_gt. Then, I open up the tester composition supplied with the plugin, which demonstrates a sphere being clipped multiple ways.