Re: Digest for vpython-users@googlegroups.com - 4 updates in 1 topic

[Richard Green]

Brute-force solution: The extrusion is basically a projection of the original 2D curve onto a series of way-point planes. The section view of the extrusion could be computed by computing one of those projections (a transform of the 2D) and then transforming that, in turn, onto the plane of your cross-section view.

On Thu, Jun 11, 2015 at 12:18 AM, <vpytho...@googlegroups.com> wrote:

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• About cross sections of 3d objects in Vpython - 4 Updates

About cross sections of 3d objects in Vpython

Vpython beginnwer <ahirudego...@gmail.com>: Jun 09 11:30PM -0700 I just start to use vpython to construct the 3D objects in computer. I'd like to know the method to how to get the cross sections of the objects. Extrusion command constructs 3D from 2D object. Therefore, extrusion seems not to help me.   I'm looking forward to your reply. Sincerely,

Bruce Sherwood <bruce.s...@gmail.com>: Jun 10 10:22AM -0600 I'm not sure what you're looking for, since what is normally called the "cross section" of a box object is a rectangle, the cross section of a sphere or cylinder is a circle, etc.   If you are looking for a way to find the 2D shape of any of these 3D objects when projected onto the 2D screen, there's nothing in VPython to help with that.

Vpython beginnwer <ahirudego...@gmail.com>: Jun 10 05:15PM -0700 Thank you so much for your kind reply. Sorry for my not good explanation. I assumed more complicated objects, such as moving spheres in cubes. And I don't mean the projection onto the 2D screen. I mean the cutting of the objects and obtains horizontal or longitudinal or vertical sections of the objects in the cutting plane.

Bruce Sherwood <bruce.s...@gmail.com>: Jun 10 08:31PM -0600 This geometrical application is too specialized to be built into VPython. However, VPython does provide all the standard operations for 3D vector calculations; in the VPython Help see Work with 3D objects > Vector Operations.   On the other hand, perhaps you should describe why you need this capability, in which case we may be able to propose a different way of getting the results you want.

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[Vpython beginnwer]

Thank you so much, Richard for you kind suggestion.
My purpose is to slice the very complicated 3D objects (like subcellular structures) to 2D view.
Therefore, Extrusion functions seems not to help me.

Thanks again.