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3D Rotation Formulas

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2 replies to this topic

#1acw83  Members

Posted 15 December 1999 - 02:03 PM

Matrices really just confuse me. So, does anyone have the straight up equations to rotate a point around the x, y, and z axis? This is my ultimate goal:

BOOL RotatePoint(CVector* point, float xa, float ya, float za);
{
point.screen_x = // Rotated x around xa, ya, and xa.
point.screen_y = // Same as above but for y
point.screen_z = // Ditto

return TRUE;
}

Any help would be great! Thanks!

#2Dave Astle  Distinguished Rhino

Posted 15 December 1999 - 12:38 PM

The equations are pretty trivial, and you should be able to derive them yourself with a little trig. BUT, since I'm nice, I'll give them to you.

For rotation around the z-axis:

x' = x cos za - y sin za;
y' = x sin za + y cos za;

For rotation around the x-axis:

y' = y cos xa - z sin xa;
z' = y sin xa + cos xa;

For rotation around the y-axis:

x' = x cos ya + z sin ya;
z' = - x sin ya + z cos ya;

Of course, x', y' and z' are the new coordinates. I'll let you figure out how to plug this into your code. It's not hard, but not as simple as you hoped.

#3acw83  Members

Posted 15 December 1999 - 02:03 PM

Thanks, you are the man. That was exactly what I was looking for!

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