Help please: Matrix issues............. :((((

Lyve · 2003-03-18T18:59:39

Hello people, I'm trying some matrix things at the moment and I just don't get it whats wrong with my code. A simplified example in pseudo-code: // store previous matrix float mOld[16]; glGetFloatv( GL_MODELVIEW_MATRIX, mOld ); // modify OpenGL matrix in some way... glMultMatrixf( m_myOwnMatrix ); // get the new matrix float mNew[16]; glGetFloatv( GL_MODELVIEW_MATRIX, mNew ); // Now let's see if we can extract "m_myOwnMatrix" from the new OpenGL matrix for testing mOld.Invert(); // remove previous matrix from new matrix mNew *= mOld; ASSERT( mNew == m_myOwnMatrix ); Note, this is no real C code. I'm using my own matrix class that is able to handle multiplication and the .Invert() thing. The last assert fails and I don't really know why. What am I doing wrong? _____________________________________ Visit http://www.nilsschneider.de for finest trance music, studio, bio, guestbook and more! [edited by - Lyve on March 16, 2003 3:21:26 PM]

NeHe Productions Affiliates

Started by Lyve March 16, 2003 02:20 PM

11 comments, last by Lyve 21 years, 11 months ago

v_d_d

122

March 18, 2003 01:26 PM

The assertion fails if the address of the two arrays are not the same.

float oldA[16];

float newA[16];

ASSERT(oldA == newA); // this fails for sure

Lyve

Author

116

March 18, 2003 03:54 PM

As said before, the assert was only pseudo-code, the assert is NOT what I''m doing in my real code, I only wanted to make clear that the two matrices are not the same!

_____________________________________
Visit http://www.nilsschneider.de for finest trance music, studio, bio, guestbook and more!

_____________________________________http://www.winmaze.de, a 3D shoot em up in OpenGL, nice graphics, multiplayer, chat rooms, a nice community, worth visiting! ;)http://www.spheretris.tk, an upcoming Tetrisphere clone for windows, a 3D tetris game on a sphere with powerful graphics for Geforce FX and similar graphics cards.

RipTorn

722

March 18, 2003 06:59 PM

yes. the inverse you are using there is the transpose.
and don''t forget that floating point numbers arn''t infinite precision. so while you might get very similar answers, they almost certainly won''t be the same.

| - Project-X - my mega project.. getting warmer

- | - adDeath - an ad blocker I made - | - email me - |

Help please: Matrix issues............. :((((

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Help please: Matrix issues............. :((((

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines