Another note:
In my opinion, the specification for indexed geometry is lacking in several
respects.
First an foremost, there is a tight but silly dependency between the
reference data sets; see GeometryArray.set*Ref*() methods. You'll see
that, for example, if your indexed geometry has 10,000 coordinates, you
must have (at least) 10,000 color values, *even if they are all identical*.
I honestly think this kind of defeats the purpose of indexed datastructures
in the first place.
Secondly, the lack of indexed geometry support on graphics cards is a well
known phenomenon. David covers it, and the Java3D software side of things,
quite well below.
Third, the documentation and examples for indexed geometry are less than
satisfactory. For example, in all the example, demo, and tutorial code
only a single class uses by-reference texture coordinates and no
documentation covers such (but for the sparse spec that is a cut-and-paste
of the API docs).
Joe
--
Joseph R. Kiniry
Chief Scientist
DALi, Inc.
--On Tuesday, December 19, 2000 01:17:10 PM -0500 "Yazel, David J."
<[EMAIL PROTECTED]> wrote:
> Well like I said in an earlier posting, it is rather disadvantageous to
> use the indexed sets. This is because it is NOT sent to the card this
> way, but rather unravelled. This means that your memory is being more
> than doubled from your index size and there is time spent to "unravel"
> the index into non-indexed.
>
> But that aside there are two things I found out. The first one is that
> you cannot stop J3d from always applying the entire array starting at the
> specified index. This means that they are NOT considering vertex count
> when you call the set routines. So if your array is 100, but you have a
> vertex count to 50, you will get an error. The index parameter to the
> SET routines indeciates the "starting" index to start assigning the
> coordinates. So if you have 100 index verticies, and you do a set a
> setCoordinates(50,norms) then you are starting at index 50.
>
> The next thing is that for texture coordinates the Set number is used for
> multi-texturing, so if you have one texture then zero is thr right value.
>
> And for specifying the normals, texcoords, colors and vertices via the
> indexes. make sure that for every vertex in your index, you have
> corresponding maps from your index to your actual data. So the easiest
> case is when you have your data laid out so that the normals, colors,
> texcoords and coordinates for all "real" vertices all match perfectly. So
> for vertex "1" the first set of normals, colors, texcoords and
> coordinates all map to that vertex. Then the same index mapping can be
> used for all the setXXXXIndices. This might not be the best strategy,
> like for example if every vertex has the same color, then obviously all
> you need is one entry of 3 (or 4) floats to define that color, and all
> the other vertices can reference that. But like I said, why bother....
> they will just turn that 4 floats into 4000 (for 1000 vertices) floats
> before they send it to the card.
>
> I have a module that stores the data in indexed form then either returns
> an IndexGeometryArray or an unwound GeometryArray. I can send it to you
> this evening if you want to use it as a reference.
>
> Dave Yazel
>
>
>
>> ----------
>> From: Liming CHEN[SMTP:[EMAIL PROTECTED]]
>> Reply To: Discussion list for Java 3D API
>> Sent: Tuesday, December 19, 2000 12:36 PM
>> To: [EMAIL PROTECTED]
>> Subject: [JAVA3D] use of IndexTriangleArray class
>>
>> Does any one know IN DETAILS how to use the IndexTriangleArray (or say
>> IndesGeometryArray) class?
>>
>> Simply spcifying a geometry with coordinates and coordinates index is
>> easy.
>> What make me confused is how to specify the Normal, normal index, texture
>> coordinates and coordinate index.
>>
>> For example, if I have a geometry with 20 veritces, 32 vertex indices and
>> 50
>> normals and 50 texture coordinates and the corresponding arrays of
>> coordinates
>> and indices.
>>
>> that is:
>>
>> int versCount = 20, IndicesCount = 32, normalCount = 50, TextureCount =
>> 50;
>> float coord[20], texCoord[3*50], normal[2*50];
>> int normalInd[3*32], texCoordInd[3*32], coordInd[3*32];
>>
>> I construct a shape3D with the following geometry class
>>
>> IndexedTriangleArray partTriangles = new
>> IndexedTriangleArray(vertsCount, GeometryArray.COORDINATES |
>> GeometryArray.TEXTURE_COORDINATE_2 | GeometryArray.NORMALS,
>> indicesCount);
>>
>> partTriangles.setCoordinates(0, coord);
>> partTriangles.setCoordinateIndices(0, coordInd);
>>
>> When I begin to set the normals for the geometry, I am not sure what the
>> first
>> variable index in setNormals(index, norms) means. Should it be 32 (the
>> vertex
>> indices) or 50 (the normal count)?
>>
>> The same problem also apply to the specification of texture coordinates.
>> That
>> is, in the method setTextureCoordinates(texCoordSet, index, texCoord)
>> what the
>>
>> index variable means? Furthermore, in Java3D1.2 there ia another variable
>> texCoordSet, what it is? In my case should it be 50 or anything else?
>>
>> Thanks in advance
>>
>> Liming
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