3D Rotations

[tcollins]

Ok, I'm confusecd about the mathematics required for 3D rotations. I have:

void xrot(D3DMATRIX &mat, double rot)
{
mat._11 = 1; mat._12 = 0; mat._13 = 0; mat._14 = 0;
mat._21 = 0; mat._22 = cos(rot); mat._23 = sin(rot); mat._24 = 0;
mat._31 = 0; mat._32 = -sin(rot); mat._33 = cos(rot); mat._34 = 0;
mat._41 = 0; mat._42 = 0; mat._43 = 0; mat._44 = 1;
}
void yrot(D3DMATRIX &mat, double rot)
{
mat._11 = cos(rot); mat._12 = 0; mat._13 = -sin(rot); mat._14 = 0;
mat._21 = 0; mat._22 = 1; mat._23 = 0; mat._24 = 0;
mat._31 = sin(rot); mat._32 = 0; mat._33 = cos(rot); mat._34 = 0;
mat._41 = 0; mat._42 = 0; mat._43 = 0; mat._44 = 1;
}
void zrot(D3DMATRIX &mat, double rot)
{
mat._11 = cos(rot); mat._12 = sin(rot); mat._13 = 0; mat._14 = 0;
mat._21 = -sin(rot); mat._22 = cos(rot); mat._23 = 0; mat._24 = 0;
mat._31 = 0; mat._32 = 0; mat._33 = 1; mat._34 = 0;
mat._41 = 0; mat._42 = 0; mat._43 = 0; mat._44 = 1;
}
which cause a rotation around their respective axies. Do I assume they are in the form:
11 12 13 14
21 22 23 24
31 32 33 34
41 42 43 44
??? or am I orientated wrong? The thing is, when I rotate, I'm not seeing what I expect. One problem is if I have a 2D plane along the Z axis at 0, and I multiply the 'rotation around the x axis' by it, I get, well, 0 multiplied by anything is 0. I loose the depth. I want to rotate a plane (like a floor) around the X-axis. Is there any good online help? Or can you help?

Thanks

Taylor

 

[werbfred]

Can you specify what you get and you want to abtain, cause it's a little bit confusing what you wrote ...

 

[werbfred]

It would be nice if you could specify a little better your purpose. You're talking about a plane along the Z axis, but a plane is 2D so the plane should be along Z and X or Z and Y, or better is Z the normal of the plane ?

When you do 3D programming you have to be very precise. You won't get something work if you're approximative !

 

[werbfred]

Just to enable E-mail notification on that post

 

[tcollins]

I eventually ended up preforming three operations in one with:

void rotate(D3DLVERTEX &v, double rx, double ry, double rz, D3DVECTOR &transformation)
{
float x1, y1, z1;

// v.x *= transformation.x;
// v.y *= transformation.y;
// v.z *= transformation.z;

x1 = cos(ry) * v.x - sin(ry) * v.z;
z1 = sin(ry) * v.x + cos(ry) * v.z;
v.x = cos(rz) * x1 + sin(rz) * v.y;
y1 = cos(rz) * v.y - sin(rz) * x1;
v.z = cos(rx) * z1 - sin(rx) * y1;
v.y = sin(rx) * z1 + cos(rx) * y1;

v.x += transformation.dvX;
v.y += transformation.dvY;
v.z += transformation.dvZ;

}

My confusion was probably one of having the matricies that allowed rotation around a particular access, but with me using it wrong. For example, if I were to rotate around the z-axis, I should see the image rotate on end parallel to my eye level, though everytime I used it, it looks like it was performing x and y-axis rotations in one, which is wrong. With that said, my project is starting to become successful, however even now I'm starting to see a performance issue with all the sine and cosine calls. I will need to look at optimizing code very soon here. The conclusion? I got around the matricie problem by using a simpler soluion, I belive, but might not be as 'elegant'?

Thanks.