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Matrix problem

Started by Wibbs Nov 27, 2011 at 1:48 PM 1 replies 1.5k views

Original Post

Nov 27, 2011 at 1:48 PM

Hey all,

I have a matrix problem that I've been trying to work out for about a week now but with no success, and I was hoping someone might beable to shed some light on it for me.

I have a scene graph where individual nodes store their scale, rotation and translation relative to their parent node. I also store the total forward and reverse transformation for each node so I can convert freely between global and local coordinates.

What I am struggling with is how to rotate a particular node around an arbitrary point in global coordinates. I know how to get:
- The matrix that represents the rotation about the point in global coordinates(Trans(-point) * Rotate * Trans(point)
- The global coordinates of the node I want to rotate

What I don't understand how to calculate is the change in local scale, rotation and translation for the node being rotated that gives the equivalent transformation.

Any help would be greatly appreciated.

Wibbs

Ripiz

100

Ripiz

Nov 28, 2011 at 3:28 PM

Do you mean rotating around point (10, 5, 0) for example?
If yes, then translate, rotate, and translate back (Translate(10, 5, 0) * Rotate(x, y, z) * Translate(-10, 5, 0))

GustavoCanedo

Nov 28, 2011 at 7:30 PM

Do you mean rotating around point (10, 5, 0) for example?
If yes, then translate, rotate, and translate back (Translate(10, 5, 0) * Rotate(x, y, z) * Translate(-10, 5, 0))

I think that isn't the problem. And another way to do this with one operation:
$fbaee547c3c65ad3d48112502363378a.png$

u = [ux,uy,uz] = unitary translation vector.

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