I have read an article about Quaternion in this site by Diana Gruber.She said Quaternion are needn''t in game programming...... This is some word in her article: -> Question: Quaternion operations are faster because they can be done using fewer operations. Answer: Disregarding my informal proof that the minimum operation count will be exactly the same, don''t forget to consider the operation count in converting quaternions to a matrix format in order to make them compatible with DirectX or OpenGL, or to add translation information, for example. <- Is this exactly or unilateral? Especially the words "don''t forget to consider the operation count in converting quaternions to a matrix format in order to make them compatible with DirectX or OpenGL, or to add translation information." goddess just one... goddess just one...

> Question: Quaternion operations are faster because they can be
> done using fewer operations.

> Answer: Disregarding my informal proof that the minimum
> operation count will be exactly the same, don''t forget to
> consider the operation count in converting quaternions to a
> matrix format in order to make them compatible with DirectX or
> OpenGL, or to add translation information, for example.

Her analysis is wrong. There are many operations for which quaternions are faster, including most associated with manipulating 3D rotations. In particular combining, comparing, and interpolating between rotations are all easiest to do with quaternions. More generally quaternions are more compact, so are quicker to copy into and out of memory (they load into a vector register in a single cycle on a modern CPU) and suffer less from numerical drift and normalisation problems.

I wish Diana Gruber''s article was removed, as it contains so much mis-information that it is of little use, and is especially confusing for people who don''t have enough experience using quaternions to recognise where she is wrong.

There''s also an interesting article that discusses several issues about rotation:

http://www.magic-software.com/Documentation/RotationIssues.pdf

What johnb said.

-Jonathan.

quote:

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Original post by johnb
I wish Diana Gruber''s article was removed, as it contains so much mis-information that it is of little use, and is especially confusing for people who don''t have enough experience using quaternions to recognise where she is wrong.

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You''re right. I''ve been meaning to do something about it for a while, and now I have.