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D3DXMatrix functions do nothing

Started by Lyev Jun 5, 2012 at 11:58 AM 4 replies 2k views

Original Post

Jun 5, 2012 at 11:58 AM

When I call these functions the matrix, v_mat_world, remains unchanged, please help :S


 float origin[3] = {1, 0, 0}, angles[3] = {D3DXToRadian(180), 0, 0}, scale[3] = {1, 1, 1};
 
 D3DXMatrixIdentity (&v_mat_world);
 D3DXMatrixTranslation (&v_mat_world, origin[0], origin[1], origin[2]);
 D3DXMatrixRotationX (&v_mat_world, angles[0]);
 D3DXMatrixRotationY (&v_mat_world, angles[1]);
 D3DXMatrixRotationZ (&v_mat_world, angles[2]);
 D3DXMatrixScaling (&v_mat_world, scale[0], scale[1], scale[2]);

Nik02

Jun 5, 2012 at 12:29 PM

You overwrite the matrix with each function call. The last operation sets the matrix to identity since the scaling factors happen to be 1.

In order to combine the effects of the transformations, you have to multiply the matrices together by your own code.

Lyev

Jun 5, 2012 at 12:38 PM

So something like this?


 D3DXMATRIX trans, rotx, roty, rotz, scaling;
 D3DXMatrixIdentity (&v_mat_world);
 D3DXMatrixTranslation (&trans, origin[0], origin[1], origin[2]);
 D3DXMatrixRotationX (&rotx, angles[0]);
 D3DXMatrixRotationY (&roty, angles[1]);
 D3DXMatrixRotationZ (&rotz, angles[2]);
 D3DXMatrixScaling (&scaling, scale[0], scale[1], scale[2]);
 
 D3DXMatrixMultiply (&v_mat_world, &v_mat_world, &rotx);
 D3DXMatrixMultiply (&v_mat_world, &v_mat_world, &roty);
 D3DXMatrixMultiply (&v_mat_world, &v_mat_world, &rotz);
 D3DXMatrixMultiply (&v_mat_world, &v_mat_world, &scaling);
 D3DXMatrixMultiply (&v_mat_world, &v_mat_world, &trans);

Nik02

Jun 5, 2012 at 1:11 PM

Yea, but you don't need the first identity step. You can use the translation as the baseline.

Nik02

Jun 5, 2012 at 1:13 PM

In addition, if you are using C++, the * operator of D3DXMATRIX is overloaded to multiply matrices, so you don't need to explicitly use D3DXMatrixMultiply.

Lyev

Jun 5, 2012 at 1:15 PM

Okay, thanks for your help!

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