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Forum Index : Microcontroller and PC projects : CMM2 Maths Issue (MATH Q_ROTATE)

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x4nd
Newbie

Joined: 05/07/2020
Location: United Kingdom
Posts: 11

Posted: 06:37pm 24 Aug 2020

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Hi All,

I guess this is a question for Peter Mather, given he's the "Maths Wiz"?

I have been exploring the rotating ball Icosahedron demo program. Making it do different things, run faster, etc. I decided to try to port it to the new maths functions, "MATH Q_ROTATE" being the main one for the main loop of the rotating ball. It looks like it should be a drop-in replacement for the existing "rotate_vector" function, but I'm getting very odd results which then made me think that I didn't understand the quaternions at all.

So, does this function work properly? If you do take that program and exchange the interpreted function for the built-in version does it work? Been scratching my head about this for quite a few hours. I don't seem to be able to get results that mean anything sensible.

Anyhow, I'm loving the CMM2 so far - it's beyond my expectations and really fun to play with.

-Stuart

If only there were more hours in the day..

matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10580

Posted: 06:41pm 24 Aug 2020

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The order of the parameters in the q array are different as they were a bit illogical in the Basic version. If you get these right then it will work. I did update the rotating ball to the MATH versions and got about a 25% speed improvement. Much of the time is taken in the plotting. Unfortunately I then overwrote the updated version so I can't post it.

x4nd
Newbie

Joined: 05/07/2020
Location: United Kingdom
Posts: 11

Posted: 06:57pm 24 Aug 2020

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No problem. I got the interpreted version up to 30fps and would like more speed! I'll have another look at the ordering of the quaternions.

I assume it should be w-x-y-z-mag. I think the interpreted version is mag-w-x-y-z?

Anyhoo - more playing.

Thanks for your time.

If only there were more hours in the day..

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