Cycling 74 » Topic: rotating cylinder in open GL

rotating cylinder in open GL

JesterN — Tue, 23 Mar 2010 22:47:00 +0000

Hi there,
i need to rotate a cylinder in open GL, but the basic rotation is around the middle point, if i need to rotate around one edge is there any solution?
i can mask half of it, but it’s gonna cover other objects
otherwise i can use linesegment in sketch but there’s no 3d in it…
Any idea?
Alberto

Re: rotating cylinder in open GL

Rob Ramirez — Tue, 23 Mar 2010 23:25:18 +0000

you can do this using gl.sketch and proper ordering of calls to gltranslate/glrotate.

to rotate something offset from it’s center point, you call glrotate before calling gltranslate with the offset amount:

– Pasted Max Patch, click to expand. –

Re: rotating cylinder in open GL

JesterN — Wed, 24 Mar 2010 14:14:52 +0000

Great robtherich, this is exactly what i needed. The sketch object seems to have a lot of possibilities, so now i see… i have another question i kept for quite some time, is it possible to group objects together in openGL in a way of using them as a macro-new-defined object? for example a Sphere and a Cylinder form a pendulum, if i link the sphere relative to the cylinder i can just rotate the cylinder thing without specifying the rotation for the sphere?

Re: rotating cylinder in open GL

Brian Chasalow — Mon, 29 Mar 2010 07:49:32 +0000

as long as you’re not doing anything too intensive, you could tell a sketch (mysketch1) to drawobject mysphere and drawobject mycylinder (name your sphere and cylinder)

then you’d call “drawobject mysketch1″ on a new SECOND sketch, “mysketch2″

nested sketches, yep.