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Thread: Getting axis coordinates

  1. #1
    Junior Member Newbie
    Join Date
    May 2008
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    3

    Getting axis coordinates

    In my graphics scene I have a drawn coordinate system (let it be XYZ) that I want to be able to rotate around imaginary axes bounded to camera. XYZ is drawn at the origin and then rotated. So if I specify (1.0, 0.0, 0.0) as vector coordinates to glRotatef call, it will rotate the scene around the current XYZ coordinate. As I understand I have to multiply (1.0, 0.0, 0.0) by inverse projection matrix and then multiply the result by inverse modelview matrix to get coordinates of the axis that coincide with screen X axis. Is that right?

  2. #2
    Junior Member Newbie fldz's Avatar
    Join Date
    Mar 2007
    Posts
    11

    Re: Getting axis coordinates

    I'm a n00b & not sure I understand the question, but what the hell.

    Something I noticed trying to build a skeleton. No matter how many nested push/pop matrix, you can read the absolute coords of any joint directly from the MODELVIEW_MATRIX.

    glGetFloatv,GL_MODELVIEW_MATRIX,offset matrix1

    offset matrix1 + 12(dwords) will be float X
    offset matrix1 + 13 Y
    offset matrix1 + 14 Z

    Maybe that's relevant.

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