Damn dirty quaternions

drb2k2 · 2005-02-10T07:58:10

Hi all, Yes i've had a look through previous posts. The problem is most of them seem to be dealing with quaternion cameras. OK now thats out the way let me explain the problem Basically I have a global axis XYZ which is tied in to the camera rotation, so for the moment lets pretend that it never changes and Y is always up, X off to the right I want to rotate objects around this axis. I have some numeric spinners to set the rotation value, so to rotate 90 degrees around the y axis just pop 90 into the y box. So far all is good. BUT, if you rotate 90 degress around the X axis, then try and rotate around the Z axis, it turns on the Y axis instead. Now I realize that this probably has something to do with an axis shifting with the model, That would be fine if all the axis did that. The y rotation spinner however will always spin around the correct axis. This means that if you rotate an object 90 degrees on the X axis, the Z rotation is now exactly the same as the Y rotation. I hope i've explained whats happening ok. Basically each object has a rotation vector. To rotate around the Y axis just add 1 to the Y value etc. The rendering part is as follows. Dim qRot As Microsoft.DirectX.Quaternion Dim RadianRot As Microsoft.DirectX.Quaternion RadianRot.X = System.Math.PI * Me.ObjectDetailsList(Me.WhichObj).Rotation.x / 180 RadianRot.Y = System.Math.PI * Me.ObjectDetailsList(Me.WhichObj).Rotation.Y / 180 RadianRot.Z = System.Math.PI * Me.ObjectDetailsList(Me.WhichObj).Rotation.Z / 180 qRot = Microsoft.DirectX.Quaternion.RotationYawPitchRoll(RadianRot.Y, RadianRot.X, RadianRot.Z) Dim RotMatrix As Microsoft.DirectX.Matrix = Matrix.Identity 'might use this later for object positional Dim Cent As Microsoft.DirectX.Vector3 Cent = New Microsoft.DirectX.Vector3(0, 0, 0) RotMatrix.AffineTransformation(1, Cent, qRot, New Microsoft.DirectX.Vector3(0, 0, 0)) // tried this and it is exactly the same //'RotMatrix.Multiply(Matrix.RotationX(Geometry.DegreeToRadian(Me.ObjectDetailsList(Me.WhichObj).Rotation.X))) //'RotMatrix.Multiply(Matrix.RotationY(Geometry.DegreeToRadian(Me.ObjectDetailsList(Me.WhichObj).Rotation.Y))) //'RotMatrix.Multiply(Matrix.RotationZ(Geometry.DegreeToRadian(Me.ObjectDetailsList(Me.WhichObj).Rotation.Z))) Me.device.Transform.World = Matrix.Multiply(RotMatrix, Me.device.Transform.World) Me.device.RenderState.Lighting = True device.SetStreamSource(0, Me.ModelVertexBuffer, 0) device.VertexFormat = CustomVertex.PositionNormal.Format device.DrawPrimitives(PrimitiveType.TriangleList, 0, Me.FacetCount) If anyone can help or point me in the right direction I would be very grateful. Cheers DRB2K2

Math and Physics Programming

Started by drb2k2 February 08, 2005 09:46 AM

11 comments, last by GameDev.net 19 years, 2 months ago

drb2k2

122

Author

February 10, 2005 01:56 AM

ok will give it a go,
i.e convert quaternions to matrices and then multiply them together.

Cheers

DRB2k2

Dmytry

1,151

February 10, 2005 02:20 AM

Quote:Original post by Anonymous Poster
Could it be that the product of tow quaternion is different than the product of two matrices.

q0 * q1 != r0 * r1

I believe this can be and was proof on another thread

Don't sure what you mean.
I tested my quaternion lib by checking that
quaternion_to_matrix(q1)*quaternion_to_matrix(q2)
is nearly equal(except for roundoff errors) to
quaternion_to_matrix(q1*q1)
Though, if you use different convention that is IMHO confusing, it might be equal to
quaternion_to_matrix(q2*q1)

Anonymous

February 10, 2005 07:58 AM

You are right I was wrong

Damn dirty quaternions

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Damn dirty quaternions

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