# Thread: make a cloud of dots

1. ## 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. 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. 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. The primitives in Collada are triangles, trifans, tristrips, polygons, polylist, lines, and linestrips. There is no points primitive unfortunately.

5. The book may be misleading, it meant to say Point Cloud as in:

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

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

6. 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. Use a <lines> element where each pair of points is the same. That'll give you the equivalent of GL_POINTS.
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. 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. 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. 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.

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