rotating an object around a point

IDontKnowJack · 2002-03-23T07:33:23

i''m trying just get this triangle to rotate around the pt. 0,3. the sides of the triangle spin and then collapse into the center of the triangle at the pt(0,3).. how do i keep them spinning where they are and not changing distance from that point.. here''s part of the code: glBegin (GL_TRIANGLES); glVertex3f(-1, 3, 3); glVertex3f(0, 4, 3); glVertex3f(1, 3, 3); glEnd(); x1 = (float)(0 + cos(angle)*(x1-0) - sin(angle)*(z1-3)); z1 = (float)(3 + sin(angle)*(x1-0) + cos(angle)*(z1-3)); x2 = (float)(0 + cos(angle)*(x2-0) - sin(angle)*(z2-3)); z2 = (float)(3 + sin(angle)*(x2-0) + cos(angle)*(z2-3)); x3 = (float)(0 + cos(angle)*(x3-0) - sin(angle)*(z3-3)); z3 = (float)(3 + sin(angle)*(x3-0) + cos(angle)*(z3-3)); thanks to anyone who can help

Graphics and GPU Programming Programming

Started by IDontKnowJack March 19, 2002 07:11 PM

11 comments, last by IDontKnowJack 22 years ago

invective

118

March 22, 2002 06:03 PM

glRotate takes the angle in degrees (yes, its actually degrees and not radians) and the axis of rotation.

glRotatef (90, 0, 1, 0);

rotates by 90 degrees with respect to the origin about the y axis.

Basiror

241

March 23, 2002 02:25 AM

so the first is the rotation angle and the second the axis around which it will be rotated thx

is there another rotation where i can specify the angle at every axis?

http://www.8ung.at/basiror/theironcross.html

davepermen

1,047

March 23, 2002 07:33 AM

there is no "angle at each axis", the euler-angles are completely wrong math, works only in integrals for differencials of angles.

axis-angles are the way to go, its always an angle around some axis, nothing more, nothing less.

for good rotation/orientation-representation, use quaternions or 3x3-rotation-matrices. you can find a lot of info about it..

to rotate around a point, bring the point to the origin, rotate around the origin, and move back..

If that's not the help you're after then you're going to have to explain the problem better than what you have. - joanusdmentia

My Page davepermen.net | My Music on Bandcamp and on Soundcloud

rotating an object around a point

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

rotating an object around a point

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines