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Rotating problems

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I am really new to opengl, just a few days so I''m having a few basic problems. Basically I got a sphere, and when I press the right/left buttons I want it to rotate it on the z axis, but I also have to rotate it along the x axis when I press up/down. My problem is that when I rotate it along one of the axis, the other rotation rotates along a weird axis. I''m having trouble describing it. Anyways what I think I''m saying is: how do i rotate an object without changing it''s axis

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Hi Chrono999,

I think the problem you''re having is due to the order which you perform the rotations. The correct order to rotate an object is:
rotate around X axis,
rotate around Y axis,
rotate around Z axis

... so in your case, your function calls would be like this:

glRotatef(xAngle, 1.0, 0.0, 0.0);
glRotatef(zAngle, 0.0, 0.0, 1.0);

If this doesn''t fix it, let me know
(I don''t want to be giving out incorrect advice)

NOTE: if you try to rotate around all three axes (like in a flight sim, etc), you''ll run into a problem called Gimbal Lock (do a search on it and quaternions if you want to know more). However, doing rotations this way is OK if you only want up to two degees of rotational freedom.

squirrels are a remarkable source of protein...

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I ran into some confusion when I first started doing this. Another problem that you may be having is that you are translating at the wrong point? But I could be wrong. I usually am.

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Hey Chrono999,

I think I know what you mean (I hope).
You probably want a rotation around the "origin-axis"?!

My OpenGL is getting a bit rusty, so I''m not sure I''m right...but it should look something like this:

float Matrix[16];
glGetFloatv(GL_MODELVIEW_MATRIX, Matrix);
glRotatef(angle, 1,0,0);

Hope it''s something usefull,

(Demo & GameDev: www.baskuenen.myweb.nl)

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