Calculating Model-View-Projection Matrix

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• 07-04-2013, 07:14 AM
Alphaomega86
Calculating Model-View-Projection Matrix
Hey,

i tried to calculate a model-view-projection matrix for my 330 OpenGL shaders, but the matrix won't work at all...
I googled too, but i didn't find something. Just a small example with the GLM-Math library, but this doesn't help me.

Here is how i calculated the mvp matrix (in LWJGL):
Code :

glGetFloat(GL_PROJECTION_MATRIX, projection);
glGetFloat(GL_MODELVIEW_MATRIX, modelview);

Matrix4f mvp = new Matrix4f();                             //Load mvp matrix as identity matrix.
Matrix4f mm = new Matrix4f().load(modelview);       //Load the model view matrix from the FloatBuffer containing the model view matrix.
Matrix4f pm = new Matrix4f().load(projection);        //Load the projection matrix from the FloatBuffer containing the projection matrix.

mvp.multLocal(mm).multLocal(pm);

At all my calculation looks like:
Code :

Read the projection matrix.
Read the modelview matrix.
Load a matrix as identity matrix.

MVP = identity * projection * modelview.

Hopefully someone can help me!
• 07-05-2013, 08:05 PM
tonyo_au
Code :

MVP = identity * projection * modelview.

This should be

Code :

MVP = projection * modelview * identity

If you are using c++ have a look at GLM library
• 07-05-2013, 08:19 PM
GClements
Quote:

Originally Posted by tonyo_au
Code :

MVP = identity * projection * modelview.

This should be
Code :

MVP = projection * modelview * identity

There's no difference. Both are equal to just
Code :

MVP = projection * modelview

• 07-05-2013, 08:35 PM
tonyo_au
Good point - since it is an identity matrix not an arbitrary matrix:sorrow: