View Full Version : Rotating to position...

ricfow

02-04-2004, 02:11 AM

Hi,

I have a triangle with normal vector (nx,ny,nz),

i want to rotate this triangle such that

the normal vector be aligned with (0,1,0).

i.e., after the rotation, all the vertices

of the triangle will have the same

y coordinate.

how can i do this ?

thanks in advance,

[],

Coconut

02-04-2004, 07:15 AM

It may not be simpliest, but here you go:

1) Find the angle, a, between (nx, ny, nz) and (0, 1, 0) using dot product,

2) If a is zero, then stops

3) if a is 180 degrees, then rotate the triangle by 180 degrees.

4) Else, find the cross product of (nx, ny, nz) and (0, 1, 0)

5) Rotate triangle around the cross product by a.

ricfow

02-08-2004, 02:30 PM

Thanks,

it worked,

Freelancer

02-19-2004, 12:00 AM

By the way, if I have a "(0,1,0)-normaled" triangle, and I want to face it to (nx, ny, nz)-normal, what should I do?

Coconut

02-19-2004, 03:19 AM

Originally posted by Freelancer:

By the way, if I have a "(0,1,0)-normaled" triangle, and I want to face it to (nx, ny, nz)-normal, what should I do?

Same thing except (nx, ny, nz) becomes (0, 1, 0) and (0, 1, 0) becomes (nx, ny, nz).

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