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matrices with glLoadMatrix()

Started by webwraith Nov 20, 2008 at 9:38 AM 4 replies 1.8k views

Original Post

Nov 20, 2008 at 9:38 AM

I'm using matrices to set my objects and camera, but when I create a 4x4 matrix and apply the translation and the 3x3 rotational matrix, I end up translating the camera before it rotates. Obviously, this isn't helpful when I need a FPS-like camera. How would I set up my matrix/matrices to translate after rotating?

swiftcoder

Nov 20, 2008 at 10:01 AM

Apply the translation and rotation in the opposite order.

webwraith

Nov 20, 2008 at 10:15 AM

Which would be great, but if the translation is only applied to three values in the matrix it wouldn't make a difference what order I apply the translation in.

Brother Bob

Nov 20, 2008 at 10:47 AM

Then you are not properly applying the transformations. Applying translation is not about changing three values in a matrix, you create a translation matrix and multiply it with the other matrix.

webwraith

Nov 20, 2008 at 5:23 PM

The function I came up with is;

        template < class _type >        void TranslateM( basic_matrix < _type, 4, 4 >& tmat, basic_vector < _type, 3 > tvec )        {                basic_matrix < _type, 4, 4 > trans;                sw_math::LoadIdentityM(trans);                trans(12) += tvec(0);                trans(13) += tvec(1);                trans(14) += tvec(2);                tmat = tmat*trans;        }

My matrix class uses a 1D array for the elements, which are considered to be in column order. Both vector and matrix classes (as shown) use overloaded parenthesis for element access, with the matrix overloading this to allow access in (row,column) convention.

Is this the right method to translate a matrix?

swiftcoder

Nov 20, 2008 at 5:37 PM

Quote:
Original post by webwraith
Is this the right method to translate a matrix?

Ja, that looks reasonable, although I can't comment on the order of multiplication.

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