# Rolling an irregular 2dshape or 3dObject , on a plane

Hi guys,
how would you approach rolling an irregular shape (not an egg nor a cube nor a sphere) , on a flat surface ? > Something like this <

im interested in writing a tool to do this, alto im not sure how it should work.
Also, any, pseudo real-time system/script/trick would be good (even if i have to bake something out to extrapolate the offset translation data from such object), obviously , it would be perfect if i could also animate the position of such object and it would rotate compensating the translation Y value in real-time, but at this stage im only interested in understanding how i can make something like this to work .

Well, how about you start with an egg or a cube? The essential principles will be the same. Later, youâ€™ll likely want to roll a convex (edit: not concave) version of the shape, rather than the shape itself.

Hi Clesage,

what im looking for is more of a guideline on how to achieve the end results, (calculate first the contact pointsâ€¦then the offset of such point so that the surface stay on topâ€¦etc) .

Yesterday i figured how to keep the poly on top of the base surface calculating an offset for my geometry, it was a simple distances comparison, taking advantage of the point on poly constraint i projected
a locator from the edge of my poly to the surface, then i calculated the radius and distance between these 3 points , and as the contact point goes to 0 i could extrapolate an offset.

Now i have 1 point only that keeps my surface on top of the otherâ€¦ the tricky part now is that i need to find a way to rotate such surfaceâ€¦ and then i would need to also find a way to interpolate between all these points as my geometry rolls on the surfaceâ€¦all these things i havenâ€™t quite figure out how to do it yet.

once i can do it on a round surface (convex ) , then ill also have to figure how to do it on a concave one (then i have no clue on how to interpolate my position/rotation based on two points contactâ€¦)

I am wondering if i would need some sort of weight blender type of thing, based on the distances of all these pointsâ€¦mh, if is not clear maybe ill try doing some sketches.

Again, if you have any hints would be appreciated .

thanks
-a

interestingly enough, i stumbled upon a maya command that does exactly this automatically.

Is not quite perfect but can be looked up on.
ill leave it here if anyone is coming across a similar problem.

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