difficult to create just a primitive, or a shape with multiple primitives

[Google Code Exporter]

What steps will reproduce the problem?
1. Read tutorial & docs, which say that a shape is "a collection of primitives" 
(see the diagrams for Materials and Effects under 
http://code.google.com/apis/o3d/docs/techoverview.html#whatisscenegraph, 
and http://code.google.com/apis/o3d/docs/devguidechap02.html#shapes).
2. Try to create a shape with multiple primitives such as cubes, cylinders, etc.
3. Find that this is done in the samples with e.g. 
o3djs.primitives.createCylinder(), but that function returns a shape, not just 
a primitive.

What is the expected output? What do you see instead?

Research further and discover there is apparently no straightforward way to do 
this; you must either (a) create multiple shapes, excise their elements and 
discard the extra shapes (counterintuitive, plus extra garbage collection 
overhead); or 
(b) duplicate a fairly long stretch of code used for creating a primitive 
(VertexInfoBase.prototype.createShapeByType()), except for a couple of lines 
related to wrapping it in a shape. 

The attached patch adds VertexInfo.createPrimitiveByType(), which would allow 
the developer to create multiple primitives individually, then easily wrap them 
in a shape. It would also allow current samples and others who have the common 
one-primitive-per-shape use case to continue using the 
convenient VertexInfo.createShape(). (The patch makes the existing 
createShapeByType() into a short wrapper for createPrimitiveByType().)

(The patch is tested against the "Primitives" sample.)

One could also add createCubePrimitive(), createCylinderPrimitive(), 
etc., but I don't think that's as critical to have as part of the 
official library. 
Maybe they could be provided in a sample. 

What version of the product are you using? On what operating system?

svn revision 50044 of o3djs library, on Windows 7.

What hardware are you using:  graphics card type?  motherboard type?
not applicable

Please provide any additional information below.

Attached a patch to o3djs/primitives.js

Original issue reported on code.google.com by [e-mail] on 23 Jun 2010 at 6:51

Attachments:

• primitives.js.patch