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# Getting transformed vertex coords

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3 replies to this topic

### #1wolfman8k  Members

Posted 18 November 2001 - 07:20 AM

How do I get the transformed vertex coordanites after calling glTranslate*() and glRotate*(). I need something like this:
  xtranformed = transform_vertex_x(x, y, z); ytranformed = transform_vertex_y(x, y, z); ztranformed = transform_vertex_z(x, y, z); 
where x, y, and z is the vertex that I want to be transformed. Can I just multiply it by the current model matrix? If so, how do I do that? thanks

### #2zedzeek  Members

Posted 18 November 2001 - 08:53 AM

simpliest way is gluUnProject(..)

### #3Qoy  Members

Posted 18 November 2001 - 06:59 PM

gluUnProject gives you vertex coords from screen coords, not vertex coords transformed by the modelview matrix.

Your best bet is probably to use glGetFloatv to get the modelview matrix and manually multiply your vertices by the matrix to transform them. Unfortunately, this involves writing matrix/vector multiplication code if you don't already have it.

Good luck.

Edited by - Qoy on November 19, 2001 2:00:32 AM

### #4Fruny  Moderators

Posted 18 November 2001 - 07:19 PM

You can recover the transformation matrices with glGet.

  double array[16];glGetDoublev( GL_MODELVIEW_MATRIX, array );

Then do a multiplication.

Be careful though, IIRC, the matrices returned are transposed

0 4 8 12
1 5 9 13
2 6 10 14
3 7 11 15

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