Heading Pitch Bank

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Viking Dan

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Heading Pitch Bank

Please make a preference option to have Cheetah display values in your preferred units. I prefer Rotation listed in X,Y, and Z (instead of HPB) for example.

Thanks.
 
HPB versus XYZ

I agree that HPB ,which may be used in game playing and flight, (I am not a video gamer or a pilot) is inconsistant with the standard XYZ which has been used in 3D animation since the beginning of such programs. HPB is like another language to me which I must translate in my head everytime I change my coordinates.

I have tried out a few other demo 3D rendering programs. Here's the deal for the money Cheetah wins and since I believe it is has expandability I'm stickin. I like how Cheetah plays well with others, imovie, Photoshop etc.
 
Viking Dan said:
Please make a preference option to have Cheetah display values in your preferred units. I prefer Rotation listed in X,Y, and Z (instead of HPB) for example.
Click to expand...

The problem is that it is not possible to transform a XYZ F-Curve to a HPB F-Curve losslessly. You either have to use always XYZ or HPB. That's not just a matter of display in the properties editor.

The only solution to maintain backward compatibility would be to add a rotation order property to every object. Maya does that for example. I've added that some time ago but I removed it later because it just added another property to each object without adding any functionality.

HPB rotation are mathematically speaking YXZ rotation. So they are almost identical. They have the same weaknesses and strengths of any euler rotation representation. So support of XYZ adds no new functionality. Things will just became more complicated since there will be two rotation representations now.

Bye,
Martin
 
fruMurf said:
is inconsistant with the standard XYZ which has been used in 3D animation since the beginning of such programs.
Click to expand...

There is by far no standard for the rotation order. Just two examples, Lightwave and Cinema 4D which are 3D apps of the first hour (in the 80th) both use HPB rotations.

Other 3D apps I know which support HPB are Maya (but they call it YXZ), Project::Messiah, Cheetah3D of course and I'm sure there are some others I've never tested.

I personally can't see a standard.:wink:

Bye,
Martin
 
Yes the whole thing is a horrible mess, and quaternions (which have the advantage of having a uniform representation) are too much for normal people (well, me, anyway) to get their heads around in normal use. (Everything is presumably handled as quaternions internally.)

The problem which Martin is expressing is that rotation is not commutative or associative: AB != BA, A(BC) != (AB)C -- so XYZ rotation (which literally is performed in that order) is simply incompatible with YXZ.

I have a problem with the labels "HPB" because I sometimes have to think for a second to figure out which axis I'm rotating around, but I do not have a problem with the assumed order of rotation. I'd be happier with H(Y), P(X), B(Z) or something.
 
HPB or Whatever

Sorry, Your explanation is lost on me. I understand you're the programmer, engineer and author there is a lot of complex coding that has to come together to make it all work somehow but I too would be happier if HPB would have their XYZ in parenths behind them. I literally have to picture the rotation in my brain. Even if technically it isn't really XYZ I can at least get my brain around that. As a conceptual artist and storyteller there is a lot I have to think about when putting together the anim. Story is most important and believable movement is another and of course the fantasy world I am creating. So maybe the other anim 3D programs are dumming down I haven't even hit knowing one tenth of what your program can do yet.

I have a million more questions but it is almost 2 AM and I have 2 events I have to be in tomorrow. So let us know what new tweaks you wil be adding to Cheetah.
 
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