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Rotation + Translation problem

Started by MrDoomMaster Oct 17, 2005 at 6:22 PM 5 replies 650+ views

Original Post

Oct 17, 2005 at 6:22 PM

I want to first rotate an object and then translate it. This is a problem because once the object is rotated, it becomes horribly difficult to translate the object because not only the OBJECT rotated but the coordinate system has as well. Any way to solve this problem? I want to rotate my object and then translate it without the translation part getting distorted.

Zakwayda

Oct 17, 2005 at 6:32 PM

You probably have your order of operations switched around. Remember that because OpenGL uses column vectors, a rotation followed by a translation is actually:

glTranslate(...);glRotate(...);

MrDoomMaster

Oct 17, 2005 at 7:01 PM

That won't work, will it? If you translate first, you move the object. If you rotate after this, the object will then rotate AROUND the origin.

For example,

suppose I translate an object to (3, 0, 0). If I rotate after the translation around the Y axis by 90 degree,s the object will then be at (0, 0, 3).

Correct me if I'm wrong.

Thunder_Hawk

Oct 17, 2005 at 7:08 PM

Quote:
Original post by MrDoomMaster
That won't work, will it? If you translate first, you move the object. If you rotate after this, the object will then rotate AROUND the origin.

For example,

suppose I translate an object to (3, 0, 0). If I rotate after the translation around the Y axis by 90 degree,s the object will then be at (0, 0, 3).

Correct me if I'm wrong.

Translating to (3, 0, 0) esentially makes (3, 0, 0) the origin for any vector. What makes you think that it should do any different for a rotation? Try it, it works...