doing 3d physics with only translation

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MagnusWootton

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doing 3d physics with only translation
« on: October 01, 2021, 02:38:44 am »
I was doing more theory on my physics ragdoll,  and thinking about centrifugal force.  which you could call "rotational accelleration"  and I worked out something quite amazing!

You can actually do rotations (including full rotational momentum) just with ordinary velocity. (cartesian style translation, with no polar coordinates!)

If you had a stick and u want to put it in a spin,  what you do is supply a perpendicular vector to the both ends of the stick in opposite directions,  and then when it skews and stretches the stick,  recorrect it and then readjust the velocity,  and that is as good as a rotate, with momentum!

Im actually doing a full motorized ragdoll, I guess I still have to proove it,   but a ragdoll is actually one of the most complex things you ever have to code in physics!  a full flight sim probably isnt as bad,  so If I can make this whole ragdoll with just translation,   then you could probably make anything without rotate,   instead with just a restretching thing which then remodifys the velocity vector each time, due to how it resisted deforming.

cool.   :D

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WriterOfMinds

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Re: doing 3d physics with only translation
« Reply #1 on: October 01, 2021, 06:21:16 am »
Why are you trying to avoid modeling rotation directly?

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MagnusWootton

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Re: doing 3d physics with only translation
« Reply #2 on: October 01, 2021, 09:30:16 am »
What sounds simpler,  quaternions, or translation. Getting angular momentum is usually the job of 4x4 matrices getting complex, I just use velocity, and its way less code!   And it supports centrifugal force, its early days yet but I think I could possibly simulate Eulers disc with it,  ill be back with a demo tomorrow latest.   see how I go!
« Last Edit: October 01, 2021, 12:45:21 pm by MagnusWootton »

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MagnusWootton

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Re: doing 3d physics with only translation
« Reply #3 on: October 03, 2021, 09:40:18 am »
UPDATE: I need more time,  It is getting done but I haven't quite got it done yet,  One more day,  It's a bit tricky for me because I'm handling a ragdoll, bit more complicated,   I think its going to fit in one dx11 compute shader!!  Its amazingly optimized.

It's funny that a GPU has matrix multipliers on the ALU,  and this technique might not even use them,  I think maybe the industry has gone the wrong direction, for good or bad.  (for bad, thinking normally tho.)

If I clip an object with a translation, I send translational information to the top of the object, and its supposed to oscillate through the spring connections, and the pull the rest of the object into a spin.     I think you have to get it to propagate throughout the mesh or tree, properly, for it to happen.

Its like doing all the game or app like a cloth simulation,  it may be really good!

I need another day.

 


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