[x3d-public] Question about parametric primitives

[Christopher Bruns]

Thank you Vince for your prompt and thoughtful reply.

The TruncatedCone primitive (or, equivalently, TaperedCylinder) would be
straightforward to model based on existing structures, and could be
implemented using a TriangleSet, so that all browsers would have little
trouble rendering such a thing.

InfinitePlane, on the other hand, is not so similar to existing structures.
Basing InfinitePlane on ObscenelyLargeRectangle would be imperfect, as
would basing it on a half-invisible cube map. Perhaps only a very
specialized rendering implementation would be appropriate for such a
primitive.

At this point I'd like to begin experimenting with existing browsers that
support X3D. Are there any written in python?

Regards,
Christopher

On Thu, Sep 14, 2017 at 10:10 AM, vmarchetti at kshell.com <
vmarchetti at kshell.com> wrote:

> Chris
>
> Your work sounds interesting, and thanks for your interest in X3D.
>
> There is no node in X3D that already represents a truncated cone, and I
> cannot come up with a better combination than your idea of a cone combined
> with a clipping plane. However, it may be useful for your project to step
> back and exploit some of the advantages of X3D. It is an open standard with
> free (available at no cost) specification, and a number of open-source
> viewers available; for example Xj3D and FreeWRL. This suggests another
> development route:
>
> 1. Develop your own specification for the truncated cone, perhaps modeled
> on Cone [ http://www.web3d.org/documents/specifications/
> 19775-1/V3.3/Part01/components/geometry3D.html#Cone ] but with additional
> fields to define the truncation.
>
> 2. Modify an open source browser that will trap your custom node and
> render it with your new renderers within an X3D scene.
>
> Of course, you now have a node feature that only you can use, because only
> you have an X3D viewer for it. If your purpose is to explore and develop
> new rendering techniques then X3D will have served as your prototyping
> environment. However, if your goal is to allow others to specifically use a
> TruncatedCone node, then you may want to submit it to the Web3D Consortium
> as a proposed extension. It would gain much likelier acceptance if it did
> not depend on your specific rendering implementation, so a suggested route
> would be for you (or perhaps someone else) to develop an additional
> TruncatedCone implementation using X3D's prototyping mechanism (
> http://www.web3d.org/documents/specifications/
> 19775-1/V3.3/Part01/concepts.html#PROTOinterfacedeclsemantics ), and
> based on existing X3D nodes such as TriangleSet constructed using a script.
>
> The same consideration and idea would hold for rendering an InfinitePlane
> node.
>
> Please continue to post your ideas and questions to the mailing list; and
> we would also welcome your membership in the Web3D Consortium where you
> would be able to participate in regular teleconferences where proposed
> extensions to X3D are discussed.
>
> With Regards
>
> Vince Marchetti
> Web3D Consortium
>
> > On Sep 14, 2017, at 11:48 AM, Christopher Bruns <
> cmbruns at rotatingpenguin.com> wrote:
> >
> > I'd appreciate some advice about how to use the X3D format.
> >
> > I'm developing some renderers that use non-mesh display methods for
> certain parametric primitives, including spheres, cylinders, truncated
> cones, and infinite planes. And I'm considering using X3D as my scene file
> format. I'm pleased to see that parametric representations for spheres and
> cylinders, at least, are available in X3D. I suspect that I could represent
> parametric truncated cones using either 1) a cone primitive plus a clip
> plane, or 2) a cylinder with a projective transformation. But I would
> prefer a more direct semantic representation of a truncated cone. Is there
> a way to explicitly represent a parametric truncated cone?
> >
> > A possibly more difficult problem is representing an infinite plane as a
> scene object. I wonder if perhaps some sort of degenerate NURBS surface
> might represent an infinite plane? Alternatively I could represent a plane
> using a single vertex plus a normal vector, along with some sort of
> annotation. Is there a more direct way to represent an infinite plane in
> X3D?
> >
> > _______________________________________________
> > x3d-public mailing list
> > x3d-public at web3d.org
> > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
>
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