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Rotation about an arbitrary axis

by Stephane Savioz · in Torque Game Engine · 09/08/2005 (7:09 am) · 5 replies

So far, I've been able to rotate my object on the z axis

float deg = 45.0;
float rad = mDegToRad(deg);
float radius = 10.0;

newPosition.x = (mInitialPosition.x + mCos(rad) * radius);
newPosition.y = (mInitialPosition.y + mSin(rad) * radius);

This works...

But now, I would like to make my object rotating about an arbitrary axis, for example V(0, 10, 5);


How to code that ?...
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Torque Owner Chris Labombard
Premium Preferred
#1
09/08/2005 (8:38 am)
Stephane - I had an algorithm set up in Torque to do this.... I should still have it on a backup cd somewhere. When I get home, I will try and fish it out for you.

Torque 3D Owner Scott Richards
#2
09/08/2005 (4:18 pm) 
// Establish axis around which to rotate
EulerF axis(x, y, z);
// Normalize to the length representing the radians you wish to rotate
// This can be positive or negative. AFAIK there is no range limit.
axis.normalize(radiansToRotate);

// Create new Matrix from Euler axis
MatrixF rotationMatrix(axis);

// Rotate desired points like so:
rotationMatrix.mulV(pointToRotate);

Note that mulP will produce the same results as mulV in this case, since the matrix has no positional information. I like mulV here, just to remind me of that. And it saves 3 useless + 0 operations. Note also that your points will be rotated around 0,0,0 but I'm sure you knew that.

Torque 3D Owner Stephen Zepp
#3
09/08/2005 (5:03 pm)
Just keep in mind that not all classes of object types within Torque network rotation about all 3 axes...from memory for example the player is clamped to only rotating about the vertical axis. So even with the algorithms, you will need to make sure the class you are using has all 3 axes of rotation networked as well.

Torque Owner Stephane Savioz
#4
09/08/2005 (11:59 pm)
Thanks guys,


I am not sure I understand the math behind the code but the most important.....it works great.

thanks

Torque Owner Chris Labombard
Premium Preferred
#5
09/09/2005 (3:30 am)
Oh.. My code rotates around an arbitrary axis at an arbitrary point in space.