Message-ID: <8D53104ECD0CD211AF4000A0C9D60AE3584546@probe-2.acclaim-euro.net>
From: Shawn Hargreaves <ShawnH AT Probe DOT co DOT uk>
To: djgpp AT delorie DOT com
Subject: Re: HELP : Scaling
Date: Tue, 23 Feb 1999 13:08:54 -0000
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Reply-To: djgpp AT delorie DOT com

Lee writes:
> i've made a small modification to TransformObj(). when the object is
> rotated, it seems as if the axis is located at screen coordinates 0, 0.
>
> how do i select my own axis to rotate the object?

Do you mean an axis aligned somewhere other than along the x/y/z
primaries, or located somewhere other than through the origin?

If you want a rotation other than around x/y/z, use 
get_vector_rotation_matrix(). If you want to rotate about a point
other than the origin, shift so that your pivot point will become
the origin (ie. translate by -pivot), rotate, and then translate
back to the original location. This is where matrix concatenation
becomes really handy, because you can build up a single matrix
that contains all three of these transforms, and then apply it
to your vertices as just a single operation.


	Shawn Hargreaves.