I don't think there is any attempt at asking the J3D to reduce it to 1
normal per poly, but more that the whole line of IndexedGeometry classes
are designed to conserve memory. Without the ability to have different
size arrays for coords, normals, etc, the memory conservation is *lost*.
As a matter of fact, using IndexedGeometry classes cost *more* memory
because of the index arrays... well, not in the case of sharing vertices
anyway, but definitely for sharing normals.
I too think that there are other much more "broken" things in J3D that
deserve priority. But I do believe that sometime *soon*, J3D should
take a hard look at memory consumption.
-Lee
-----Original Message-----
From: Mark Ferneau [mailto:[EMAIL PROTECTED]]
Sent: Monday, November 06, 2000 2:08 PM
To: [EMAIL PROTECTED]
Subject: Re: [JAVA3D] Memory Issues: same number of normals and
coordinates, even for indexed Geometry?
John,
Rest assured that the J3D team would not prevent someone from having 3
normals per poly (aka normal per vertex). Removing this feature would
be
equivalent (in some senses) to saying that J3D will not support lights
other than ambient. Rather the "vote" is for whether people *also* want
the ability to specify one normal per triangle (aka normal per face or
normal per poly).
By the way, the word is 'polygonal'.
--Mark
At 12:11 PM 11/6/2000 -0600, you wrote:
>At this point in time I feel there are a lot more higher priority
>issues. I would not want Sun spending time on this at this point.
>
>It's easy to see how having three normals per polygon can eat up memory
>(waste it?) until you use those normals to smooth the hard edges. This
>is a very clear impact on image quality that we've seen using other 3DS
>loaders vs our 3DS loader. With properly angled normals at each vertex
>our models display very smooth and look great. Without this it would
>look very "polygony" (is that a word?). So for our purposes we WANT
>three normals per triangle.
>
>So I'd have to vote *very* low priority on this.
>
>- John Wright
>Starfire Research
>
>Adam Tegen wrote:
> >
> > Thanks for responding.
> >
> > Does anyone else listening to this discussion think this would be
useful?
> >
> > Adam
> >
> > -----Original Message-----
> > From: Discussion list for Java 3D API
> > [mailto:[EMAIL PROTECTED]]On Behalf Of Kevin Rushforth
> > Sent: Monday, November 06, 2000 11:29 AM
> > To: [EMAIL PROTECTED]
> > Subject: Re: [JAVA3D] Memory Issues: same number of normals and
> > coordinate s, even for indexed Geometry?
> >
> > This is a known limitation of the IndexedGeometryArray API. The
> > lengths of the coordinates, colors, normal, texcoord arrays must be
the
> > same even for IndexedGeometryArray objects.
> >
> > We could look into addressing this in Java 3D 1.3, but it will
require
> > additional API, at a minimum separate counts for each of
coordinates,
> > colors, normal, texcoord. It will also require significant changes
to
> > the implementation; currently, all of the set/get methods for vertex
> > data are in the GeometryArray base class. These would either have
to
> > be modified to know about the separate counts for each component or
> > they would have to be overridden in the IndexedGeometryArray class.
If
> > there is enough demand for this, we could look into doing it (at
least
> > for the by-ref case).
> >
> > --
> > Kevin Rushforth
> > Java 3D Team
> > Sun Microsystems
> >
> > [EMAIL PROTECTED]
> >
> > >Date: Mon, 6 Nov 2000 08:22:10 -0500
> > >From: "J. Lee Dixon" <[EMAIL PROTECTED]>
> > >Subject: Re: [JAVA3D] Memory Issues: same number of normals
and
> > coordinate
> > > s,
> > > even for indexed Geometry?
> > >To: [EMAIL PROTECTED]
> > >
> > >Yep, I can definitely agree with you there. If you are using an
> > >IndexedGeometryArray subclass, it would make sense to be able to
have
> > >multiple faces that point the same direction (i.e. share the same
> > >normal).
> > >
> > >Yet, the API spec says that if your normals.length <
(3*vertexcount),
> > >you will get an exception. This makes no sense for indexing.
> > >
> > >Can somebody at Sun PLEASE address this design issue???
> > >
> > >-Lee
> > >
> > >-----Original Message-----
> > >From: Adam Tegen [mailto:[EMAIL PROTECTED]]
> > >Sent: Friday, November 03, 2000 5:34 PM
> > >To: [EMAIL PROTECTED]
> > >Subject: Re: [JAVA3D] Memory Issues: same number of normals and
> > >coordinate s, even for indexed Geometry?
> > >
> > >
> > >Thanks very much for the reply.
> > >
> > >One thing though:
> > >
> > >I am using setNormalRefFloat(), so in this example I have to create
> > >
> > >float[] locations = new float[24];
> > >float[] normals = new float[24]; //not 18, because its by ref.
> > >
> > >so I waste the space for 6 floats (4 bytes each) for 24 bytes.
> > >
> > >Since I am doing cad data, dealing with possibly hundreds of megs
of
> > >data,
> > >this wasted space can amount to a lot.
> > >
> > >If anyone at sun could chime in, I would appreciate it. The part I
> > >don't
> > >understand is why there is this issue in the first place. Indexed
data
> > >shouldn't care, unless I am missing something. XSG, for instance,
> > >doesn't
> > >care.
> > >
> > >Thanks much,
> > >
> > >Adam
> > >
> > >
> > >-----Original Message-----
> > >From: Discussion list for Java 3D API
> > >[mailto:[EMAIL PROTECTED]]On Behalf Of J. Lee Dixon
> > >Sent: Friday, November 03, 2000 4:55 PM
> > >To: [EMAIL PROTECTED]
> > >Subject: Re: [JAVA3D] Memory Issues: same number of normals and
> > >coordinate s, even for indexed Geometry?
> > >
> > >
> > >Each "vertex" has a location (or coordinate), and optionally a
normal,
> > >color, and texture coordinate.
> > >
> > >After looking at the API specs for IndexedGeometryArray, I think it
> > >works like this (somebody at Sun feel free to chime in):
> > >
> > >Vector3d[] locations = new Vector3d[8] { ... 8 locations ... };
> > >Vector3d[] normals = new Vector3d[6] { ... 6 normals ... };
> > >
> > >int index_count = 4 (vertices_per_face) * 6 (faces) = 24;
> > >cube = new IndexedQuadArray(locations.length, COORDINATES |
NORMALS,
> > > index_count);
> > >
> > >// Now, set the locations.
> > >cube.setCoordinates(0, locations);
> > >
> > >// Now, set the normals. I think what happens here is that
> > >// the GeometryArray has allocated space for *pointers* to 8
normals,
> > >// but we only fill 6 of them.
> > >cube.setNormals(0, normals)
> > >
> > >int[] location_indices = new int[index_count]
> > >{
> > > 0, 1, 2, 3, // the quad for the first face,
> > > 1, 3, 7, 4, // the quad for the second face,
> > > 5, 4, 7, 6, // the quad for the third face,
> > > etc....
> > >};
> > >
> > >int[] normal_indices = new int[index_count]
> > >{
> > > 0, 0, 0, 0, // the normals for the vertices in the first face
are the
> > >same
> > > 1, 1, 1, 1, // second face
> > > 2, 2, 2, 2, // third face
> > > 3, 3, 3, 3, // etc...
> > > 4, 4, 4, 4,
> > > 5, 5, 5, 5
> > >};
> > >
> > >So, I think the only *wasted* space is the two normal pointers in
the
> > >normal array that are not used... Does this sound right to ppl at
> > >Sun?????
> > >The GeometryArray is (hopefully) allocating the array space, but
not the
> > >actual members of the normal array. I mean:
> > >
> > > // They have to do this because the max possible normals the
> > > // user will want is a normal for each vertex.
> > > myNormals = new Vector3d[vertex_count];
> > >
> > > // But hopefully not doing this:
> > > int i;
> > > for(i=0; i<myNormals.length; i++)
> > > {
> > > myNormals[i] = new Vector3d();
> > > }
> > >
> > >*whew*
> > >-Lee
> > >
> > >-----Original Message-----
> > >From: Adam Tegen [mailto:[EMAIL PROTECTED]]
> > >Sent: Friday, November 03, 2000 2:18 PM
> > >To: [EMAIL PROTECTED]
> > >Subject: Re: [JAVA3D] Memory Issues: same number of normals and
> > >coordinate s, even for indexed Geometry?
> > >
> > >
> > >A further question:
> > >
> > >A "Vertex" is a combination of coordinate, normal, etc. right? If
you
> > >have
> > >an IndexedGeometryArray, why does the number of normals need to
equal
> > >the
> > >number of coordinates? The number of indices for each does need to
be
> > >the
> > >same for each, though.
> > >
> > >Can you explain this to me further? Other scene graphs use
per-vertex
> > >shading and do not have this restriction.
> > >
> > >Adam
> > >
> > >-----Original Message-----
> > >From: Discussion list for Java 3D API
> > >[mailto:[EMAIL PROTECTED]]On Behalf Of J. Lee Dixon
> > >Sent: Friday, November 03, 2000 1:28 PM
> > >To: [EMAIL PROTECTED]
> > >Subject: Re: [JAVA3D] Memory Issues: same number of normals and
> > >coordinate s, even for indexed Geometry?
> > >
> > >
> > >The reason for the number of normals equalling the number of
coordinates
> > >is that Java3D does per-vertex shading. This allows for smooth
shading
> > >of curved surfaces, but yes it is a little wasteful for objects
like
> > >cubes.
> > >
> > >-Lee
> > >
> > >-----Original Message-----
> > >From: Adam Tegen [mailto:[EMAIL PROTECTED]]
> > >Sent: Friday, November 03, 2000 12:11 PM
> > >To: [EMAIL PROTECTED]
> > >Subject: [JAVA3D] Memory Issues: same number of normals and
coordinates,
> > >even for indexed Geometry?
> > >
> > >
> > >Hello-
> > >
> > >I'm doing some tests with Java3D and notices something:
> > >
> > >The number of coordinates must equal the number of normals (when
> > >enabled)
> > >etc. At least this is how it seems to be when I use commands like
> > >IndexedTriangleArray.setNormalRefFloat(...)
> > >
> > >While this makes sense for non-indexed geometry, how does this make
> > >sense
> > >for indexed geometry? A cube, for instance has 8 coordinates, and
6
> > >normals.
> > >
> > >Am I understanding this correctly? Does this mean that java3D eats
up
> > >unneeded memory? Is there a good reason for this, or is this an
area
> > >for
> > >improvement for future versions.
> > >
> > >If someone could explain this to me, I would greatly appreciate it.
> > >
> > >Adam
> > >
> >
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