1. ## Inverse Matrix

Hi, can anyone actually point out why, what and where the inverse matrix is used in openGL and why it is useful? thanks!

2. ## Re: Inverse Matrix

you can use the inverse matrix M^-1 of matrix M when you want the changes that M did want to be undone.

3. ## Re: Inverse Matrix

Ooh right thanks What about the determinant of a matrix, how is that useful in 3d graphics/games?

4. ## Re: Inverse Matrix

The determinant almost serves for calculating the inverse of a matrix.

5. ## Re: Inverse Matrix

It is used to determine whether a polygon is backfacing.

6. ## Re: Inverse Matrix

could you possibly explain how? The thoery behind it? If it's too lengthy explanation it doesn't matter

7. ## Re: Inverse Matrix

The explanation is a bit involved and it requires some knowledge of Linear Algebra.

I won't get into all of that here but I can refer you to this
should you care to read up on it.

8. ## Re: Inverse Matrix

The inverse transformation matrix is necessary for vertex normal transformation.

The vertex itself is multiplied with the modelview-projection-matrix. Normals need to be multiplied with the inverse transpose of that matrix to stay correct.

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