5 replies to this topic

[Lyev]

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]);

Edited by Lyev, 05 June 2012 - 05:59 AM.

[Nik02]

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.

Edited by Nik02, 05 June 2012 - 06:30 AM.

[Lyev]

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]

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

[Nik02]

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]

Okay, thanks for your help!