Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: make a cloud of dots

  1. #1
    ZINS
    Guest

    make a cloud of dots

    Hi,

    I search to paint a cloud of dots.
    with the word MESH in GEOMETRY you can design : line, polygone, polylist, triangle ...
    I don't see anything in the documentation COLLADA 1.4.1 specification june 2006.
    Is it possible to design a cloud of dots ???

    I use collview to see the result.

    Thanks

  2. #2
    Senior Member
    Join Date
    Jan 2006
    Location
    Foster City, CA
    Posts
    540
    Collada doesn't have a points primitive, but it has a <lines> element. A line is specified with two endpoints, but if you make the endpoints the same then you'll get what you want.

    Steve

  3. #3
    InteractiveMesh
    Guest
    Hi,

    according to the following quotations point primitives seem to be defined !?

    - Collada book p. 52/53:

    A mesh may not have any child elements, except for a cloud of points without lines or polygons.

    The <vertices> and <source> elements are the only required child elements of the <mesh> element, because that is all that is needed to represent a cloud of points.
    - Collada spec 1.4.1 2nd, p. 5-134:

    Here is an example of a <vertices> element that describes the vertices of a mesh:
    <mesh>
    <source id="position"/>
    <vertices id="verts">
    <input semantic="POSITION" source="#position"/>
    </vertices>
    </mesh>
    August

  4. #4
    Senior Member
    Join Date
    Jan 2006
    Location
    Foster City, CA
    Posts
    540
    The primitives in Collada are triangles, trifans, tristrips, polygons, polylist, lines, and linestrips. There is no points primitive unfortunately.

  5. #5
    Senior Member
    Join Date
    Jul 2004
    Location
    Santa Clara
    Posts
    356
    The book may be misleading, it meant to say Point Cloud as in:

    http://en.wikipedia.org/wiki/Point_cloud

    which COLLADA provides.


    What would you like to do exactly?
    What point primitive are you looking for?

  6. #6
    ZINS
    Guest
    Hi,

    We want to design a sky of stars.
    Each star is a point.
    We will use opengl with the parameter GL_POINT and the function glPointSize.

    Which is the best way to to this ??

    Can we see all these points with standard COLLADA viewer ???

    Thanks

  7. #7
    Senior Member
    Join Date
    Jan 2006
    Location
    Foster City, CA
    Posts
    540
    Use a <lines> element where each pair of points is the same. That'll give you the equivalent of GL_POINTS.
    Quote Originally Posted by ZINS
    Can we see all these points with standard COLLADA viewer ???
    It depends on the viewer and whether or not it supports the (somewhat rarely used) <lines> element. You'll have to test and see.

  8. #8
    Junior Member
    Join Date
    Sep 2008
    Posts
    3
    Are there any plans to support points ?

    this seems a strange omission to me ( but I know nothing )

    I'm working with LIDAR files and can have millions and into hundreds of millions, having to make a 3d representation of a point rather than using something like GL_POINT will be just well eekkkk

    We have a requirements to be able to show the point cloud as points in apps Goggle Earth etc..

  9. #9
    Junior Member
    Join Date
    Jun 2006
    Location
    Morrison, CO
    Posts
    22
    will be just well eekkkk
    And so is encoding to ASCII XML

    We have a requirements to be able to show the point cloud as points in apps Goggle Earth etc..
    I think you'll be VERY disappointed in performance of GE in this case, and how much data it can really handle. I've been using COLLADA for years for the sole purpose of generating data for GE, and have wished for a better alternative (not COLLADA's fault, just not best choice for GE runtime data IMO).

    Do you _REALLY_ need to see a LIDAR point cloud in GE though? A point cloud isn't really a surface, just samples taken FROM a surface. Why not do a really low poly representative surface with a texture map consisting of point plots for instance?

  10. #10
    Senior Member
    Join Date
    Jan 2006
    Location
    Foster City, CA
    Posts
    540
    Quote Originally Posted by UrbanLegend
    Are there any plans to support points ?
    If the app you're targeting supports Collada's <lines> primitive then you can use that to simulate points. If the app you're targeting doesn't support <lines> then it's unlikely they'd support a <points> primitive if we added one to the spec.

    But I agree that a <points> primitive would be nice.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •