937 lines
28 KiB
HTML
937 lines
28 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|
<HTML>
|
|
<HEAD>
|
|
<META http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
|
<TITLE>A Simple Scene Graph API for OpenGL.</TITLE>
|
|
</HEAD>
|
|
<BODY text="#B5A642" link="#8FFF8F" vlink="#18A515" alink="#20336B"
|
|
bgcolor="#005000" background="../marble.png">
|
|
|
|
<H2>Non-class Functions.</H2>
|
|
So, with the class functions described above, it is
|
|
fairly simple to construct a scene graph. So, now that
|
|
you have one, what can you do with it?
|
|
<pre>
|
|
void ssgCullAndDraw ( ssgRoot *root ) ;
|
|
</pre>
|
|
This call deals with the entire process of rendering the database.
|
|
Your application need only call ssgInit(), build a database,
|
|
create a current context and call ssgCullAndDraw using the root node
|
|
of that database.
|
|
<H3>Intersection Testing.</H3>
|
|
Most applications need to test the scenery to see if moving
|
|
objects have collided with it - there are several ways to do
|
|
that - but they all share the same mechanisms:
|
|
<pre>
|
|
|
|
int ssgIsect ( ssgRoot *root, sgSphere *s, sgMat4 m, ssgHit **results ) ;
|
|
int ssgHOT ( ssgRoot *root, sgVec3 s, sgMat4 m, ssgHit **results ) ;
|
|
int ssgLOS ( ssgRoot *root, sgVec3 s, sgMat4 m, ssgHit **results ) ;
|
|
|
|
</pre>
|
|
These three calls implement various ways to test the database for collisions,
|
|
weapon impacts and such like. In each case, the search for a collision
|
|
starts at 'root', and the database is transformed by the matrix 'm'
|
|
before the test is evaluated - hence, 'm' is ususally the inverse of
|
|
the matrix describing the test object's location.
|
|
<ul>
|
|
<li>ssgIsect intersects a sphere against the scene.
|
|
<li>ssgHOT intersects a vertical line starting at the point 's' (remember,
|
|
in SSG, positive Z is 'up'). This is often used to compute
|
|
the Height-of-Terrain - hence the name 'HOT'.
|
|
<li>ssgLOS intersects an arbitary vector whose direction is defined by 's'.
|
|
</ul>
|
|
The result in either case is an integer telling
|
|
you how many triangles impacted the sphere/vector. If you need to know more
|
|
about these intersections, pass the address of a ssgHit * variable as
|
|
the last parameter and it will be returned pointing at a STATIC array
|
|
of ssgHit structures. Thats a confusing explanation - and an example
|
|
will help:
|
|
<pre>
|
|
|
|
ie:
|
|
|
|
ssgHit *results ;
|
|
|
|
int num_hits = ssgIsect ( root, &sphere, mat, &results ) ;
|
|
|
|
for ( int i = 0 ; i < num_hits ; i++ )
|
|
{
|
|
ssgHit *h = &(results [ i ]) ;
|
|
|
|
/* Do something with 'h' */
|
|
}
|
|
|
|
</pre>
|
|
Remember, you must finish using the results array before you do
|
|
another ssgIsect/ssgHOT/ssgLOS because all three functions share
|
|
the same results array.
|
|
<p>
|
|
By default, these functions only detect collisions with the front face
|
|
of polygons. You can make them detect only the back faces using:
|
|
<pre>
|
|
|
|
void ssgSetBackFaceCollisions ( bool b ) ;
|
|
|
|
</pre>
|
|
<p>
|
|
An ssgHit looks like this:
|
|
<pre>
|
|
|
|
class ssgHit
|
|
{
|
|
ssgLeaf *leaf ;
|
|
int triangle ;
|
|
sgVec4 plane ;
|
|
sgMat4 matrix ;
|
|
|
|
ssgHit ()
|
|
int getNumPathEntries () ;
|
|
ssgEntity *getPathEntry ( int i ) ;
|
|
} ;
|
|
|
|
</pre>
|
|
The 'leaf' member points at the leaf node that impacted the sphere.
|
|
The 'triangle' member tells you which triangle within the leaf
|
|
did the impacting. The 'plane' member contains the plane equation
|
|
of the impacting triangle and the 'matrix' element tells you
|
|
the net result of concatenating all the transform nodes from
|
|
the root to the leaf to the matrix you provided in the ssgIsect call.
|
|
<p>
|
|
It's possible for there to be multiple paths through the
|
|
scene graph to the leaf node. Sometimes you'll need to
|
|
look back up the tree to see nodes above the one that we actually
|
|
impacted with. Hence, you can read all the ssgEntities that were
|
|
traversed on the path from the root down to the leaf. Calling
|
|
the 'getNumPathEntries' function to find the number of nodes
|
|
along the path - and then 'getPathEntry(n)' to get the n'th entry
|
|
in the path. The 'root' node will always be the zeroth entry
|
|
in the path - and the leaf node will always be the last.
|
|
<H3>Lights.</H3>
|
|
SSG supports the eight standard OpenGL light sources as class 'ssgLight'.
|
|
Since there are only a finite number of these, they all exist all the
|
|
time - you just call:
|
|
<pre>
|
|
|
|
ssgLight *ssgGetLight ( int i ) ;
|
|
|
|
</pre>
|
|
...to get the i'th light should you need to manipulate it.
|
|
<pre>
|
|
|
|
class ssgLight
|
|
{
|
|
int isOn () ;
|
|
void on () ;
|
|
void off () ;
|
|
|
|
void setPosition ( const sgVec3 pos ) ;
|
|
void setPosition ( float x, float y, float z ) ;
|
|
|
|
void setColour ( GLenum which , const sgVec4 colour ) ;
|
|
void setColour ( GLenum which , float r, float g, float b ) ;
|
|
|
|
void setHeadlight ( int head ) ;
|
|
int isHeadlight () ;
|
|
|
|
void setSpotlight ( int spot ) ;
|
|
int isSpotlight () ;
|
|
|
|
void setSpotDirection ( const sgVec3 dir ) ;
|
|
void setSpotDirection ( float x, float y, float z ) ;
|
|
void setSpotDiffusion ( float exponent, float cutoff = 90.0f ) ;
|
|
void setSpotAttenuation ( float constant, float linear, float quadratic ) ;
|
|
} ;
|
|
|
|
</pre>
|
|
Each light can be turned on or off - or tested to see if it's on or off.
|
|
<p>
|
|
Lights are positioned with 'setPosition()' - which can be relative
|
|
to the origin of the world - or relative to the SSG camera (in 'headlight'
|
|
mode).
|
|
<p>
|
|
If the 'spotlight' mode is enabled,
|
|
then the light intensity has a certain distribution and attenuation.
|
|
These parameters can be set with the 'setSpotXxx' methods.
|
|
Otherwise, the light source is considered to be directional,
|
|
or infinitely far away (in the direction of its position).
|
|
The 'spotlight' mode is initially disabled.
|
|
|
|
<H3>Miscellany.</H3>
|
|
It's convenient to find out how much texture memory has been
|
|
consumed:
|
|
<pre>
|
|
|
|
int ssgGetNumTexelsLoaded () ;
|
|
|
|
</pre>
|
|
(Bear in mind that a texel could be 16 or 32 bits depending on
|
|
the hardware - and with MIPmapping enabled, 25% of the texels
|
|
will be in the MIPmaps - so ssgGetNumTexelsLoaded will return
|
|
a larger number than the total of the sizes of the input images
|
|
might suggest.
|
|
<H3>Loading Database Files.</H3>
|
|
To load a model file into SSG, you can either call a loader
|
|
function that is specific to the format of the file you
|
|
wish to load - or you can call 'ssgLoad' - which parses
|
|
the filename extension and calls the appropriate format-specific
|
|
loader.
|
|
<p>
|
|
At time or writing, there are MANY loaders for SSG:
|
|
<ul>
|
|
<li> ssgLoadSSG - for '.ssg' files - the 'native' SSG format.
|
|
<li> ssgLoadAC - for '.ac' files - a somewhat obscure format produced
|
|
by the 'AC3D' modelling tool - reasonably well tried
|
|
and tested.
|
|
<li> ssgLoad3ds - for '.3ds' files as produced by 3DStudio.
|
|
<li> ssgLoadASE - 3DSMAX ASCII EXPORT Version 2.00, well tested
|
|
<li> ssgLoadDXF - AutoCADs famous DXF format. well tested
|
|
<li> ssgLoadFLT - OpenFlight. Works for OpenFlight files generated by
|
|
recent versions of MultiGen - but not for those generated by some other
|
|
tools such as Designers' Workbench.
|
|
<li> ssgLoadMD2 - Quake MD2
|
|
<li> ssgLoadOBJ - Wavefront, works well
|
|
<li> ssgLoadTRI - simple Tri format from "Andy Colbournes Editor".
|
|
<li> ssgLoadX - Microsofts DirectX-Format. Most features work.
|
|
<li> ssgLoadOFF - Geomview's OFF
|
|
<li> ssgLoadM - ???
|
|
<li> ssgLoadATG - Ascii TerraGear. Used by Flight Gear Flight Sim.
|
|
<li> ssgLoadVRML1 - VRML1 format, only partially implemented.
|
|
<li> ssgLoadIV - Inventor format, only partially implemented.
|
|
<li> ssgLoadStrip - The format of a stripifier.
|
|
</ul>
|
|
|
|
<pre>
|
|
|
|
typedef ssgBranch *(*ssgHookFunc)(char *) ;
|
|
|
|
ssgEntity *ssgLoad ( const char *fname, const ssgLoaderOptions *options = NULL ) ;
|
|
|
|
ssgEntity *ssgLoadSSG ( const char *fname, const ssgLoaderOptions *options = NULL ) ;
|
|
ssgEntity *ssgLoadAC ( const char *fname, const ssgLoaderOptions *options = NULL ) ;
|
|
ssgEntity *ssgLoad3ds ( const char *fname, const ssgLoaderOptions *options = NULL ) ;
|
|
...etc...
|
|
|
|
</pre>
|
|
Minimally, all you need to do is to call ssgLoadAC/ssgLoad3ds with the
|
|
name of the file to load. However, most file formats (AC3D's
|
|
and 3Dstudio's included) lack many desirable features, and it is also often
|
|
necessary to store application-specific information in the
|
|
file.
|
|
<p>
|
|
SSG's loaders will decode the comment fields found in the
|
|
nodes of many common file formats and pass these onto the
|
|
application via 'hookfunc'. This function should decode
|
|
the string and construct whatever kind of SSG node it
|
|
considers appropriate.
|
|
<p>
|
|
Similarly, the application may wish to embellish the
|
|
ssgState of a loaded node - and since state information
|
|
rarely has a comment field in most file formats, we
|
|
pass the texture filename instead and expect the application
|
|
to construct the entire ssgState:
|
|
<pre>
|
|
|
|
void ssgSetAppStateCallback ( ssgState *(*cb)(char *) ) ;
|
|
|
|
</pre>
|
|
One common problem with file loaders is that it's
|
|
often possible to refer to a second file from inside
|
|
the first - but the <b>path</b> to that file is often
|
|
not adequately defined by the original file. Hence,
|
|
the application can specify a file path to be prepended
|
|
to all model or texture file names.
|
|
<pre>
|
|
|
|
void ssgModelPath ( char *path ) ;
|
|
void ssgTexturePath ( char *path ) ;
|
|
|
|
</pre>
|
|
You can only supply one path. If you need additional features, use the
|
|
function <code>ulFindFile</code> (for more see util-library-doc).
|
|
|
|
The last three functions simply set values in the _ssgCurrentOptions
|
|
(type ssgLoaderOptions), for example:
|
|
|
|
<pre>
|
|
inline void ssgModelPath ( const char *path )
|
|
{
|
|
_ssgCurrentOptions -> setModelDir ( path ) ;
|
|
}
|
|
</pre>
|
|
|
|
For more on ssgLoaderOptions see also the next page of this doc.
|
|
|
|
<p>
|
|
|
|
Some loaders for file formats that use texture formats not
|
|
supported by ssg use this functions to find textures:
|
|
<pre>
|
|
void ssgFindOptConvertTexture( char * filepath, char * tfname )
|
|
</pre>
|
|
It finds and optionally (= if necessary) converts the texture.
|
|
This is only really implemented for Windo$ :-(, for all others it
|
|
should just be the two lines you will find in the comment. I didn't
|
|
test it, that's the reason I commented it out. But it will warn you
|
|
when you have to convert something, so even for non-Windo$-users the
|
|
new function is already a step forward.
|
|
For the actual conversion, at first I wanted to use GIMP. So, in Deja,
|
|
I looked for "+gimp +convert +batch" and similar strings. I found
|
|
several people asking, but almost all the answer were to use
|
|
ImageMagick instead. ImageMagick is free as in beer. Also, the docs I
|
|
got with the newest gimp is extremely sparse :-(. Therefore, I tried
|
|
ImageMagick and this worked straight away. You should find ImageMagick
|
|
under
|
|
<p>
|
|
http://www.wizards.dupont.com/cristy/ImageMagick.html
|
|
<p>
|
|
Plib uses the ImageMagick application "convert". Since there are other
|
|
convert.exe-programs on my computer, I had to copy the ImageMagick
|
|
stuff into the directory of my plib-application, so that it uses the correct
|
|
convert.exe.
|
|
<p>
|
|
|
|
|
|
Most file formats contain considerable numbers of redundant
|
|
nodes (because of the way people build using these tools).
|
|
This function walks a database sub-tree multiplying
|
|
out any ssgTransform nodes and replacing them with
|
|
ssgBranch'ed - unless they have userdata associated with them.
|
|
Any branch nodes with zero kids are deleted - any with just
|
|
one kid are eliminated and the child node pushed up one level.
|
|
<pre>
|
|
|
|
void ssgFlatten ( ssgEntity *ent ) ;
|
|
|
|
</pre>
|
|
It's important for 3D performance to optimise
|
|
triangles into triangle strips or fans. Since most
|
|
file formats don't record strip/fan information,
|
|
it's useful to call:
|
|
<pre>
|
|
|
|
void ssgStripify ( ssgEntity *ent ) ;
|
|
|
|
</pre>
|
|
<H3>Saving Database Files.</H3>
|
|
Most SSG programs will simply load a file and display it in
|
|
some way - but occasionally, it's useful to be able to write
|
|
a file back out again.
|
|
<p>
|
|
To write a model file from SSG, you can either call a writer
|
|
function that is specific to the format of the file you
|
|
wish to save - or you can call 'ssgSave' - which parses
|
|
the filename extension and calls the appropriate format-specific
|
|
writer.
|
|
<p>
|
|
Saving into ssg-format is done with these functions:
|
|
<ul>
|
|
<li> ssgSaveSSG - for '.ssg' files - the 'native' SSG format.
|
|
</ul>
|
|
<pre>
|
|
|
|
int ssgSave ( char *fname, ssgEntity *ent ) ;
|
|
int ssgSaveSSG ( char *fname, ssgEntity *ent ) ;
|
|
|
|
</pre>
|
|
This returns TRUE if the operation worked - FALSE if it failed.
|
|
You will also find writers for the 3DS, AC, ASE, ATG, DXF, M, OBJ, OFF, QHI, TRI and
|
|
X formats.
|
|
|
|
<H3>Features of the file formats and status of the loaders/writers</H3>
|
|
|
|
Here comes a table of the features of all the file formats and loaders and writers.
|
|
VRML doesn't really work, so you won't find it here.
|
|
The "QHI" (QHull Input - a format used by a toll to create convex hulls)
|
|
writer only writes a point cloud and suppoorts no other features, so I also didn't add it to the table.
|
|
BTW, if you want to create convex hulls of existing geometry, you just need a few lines. Look
|
|
into PPE (prettypoly editor, on SourceForge as well), into the file ppeCoreFuncs.cxx,
|
|
function addConvexHull.
|
|
The SSG loaders/writers support all
|
|
features of the ssg-lib, so missing features mean they miss in the library (normaly because they miss in OpenGL)
|
|
The letters mean:
|
|
<BR><BR>
|
|
A = feature not in file format
|
|
<BR>
|
|
B = feature in file format and not implemented, not planned.
|
|
<BR>
|
|
C = feature in file format and not implemented, but planned.
|
|
<BR>
|
|
D = feature in file format and partly implemented or not tested.
|
|
<BR>
|
|
E = feature in file format and implemented.
|
|
<BR><BR>
|
|
And here are the features with some explanaitions:
|
|
<BR><BR>
|
|
|
|
<ul>
|
|
<li>Filled polys - Planar polygons. In the ssg-lib, this is the only primitive you can use to make "solid" looking models. This is a 2D primitive; it has no volume but an area.
|
|
<li># sides - No of sides per poly. This is of course equal to number of vertices per poly. Some formats support only triangles, some
|
|
also quads and some support n-sided polys, that is they have no restrictions.
|
|
<li>Lines - for example used for high voltage lines in a flight simulator.
|
|
This is a 1D primitive; it has no area but a length.
|
|
<li>Points - for example used for small lights.
|
|
This is a "0D" primitive; it has no length.
|
|
<li>Sub objects - The complete model may consist of several sub models.
|
|
There are several reasons one wants this, for example to make the structure of the model
|
|
clearer to humans, to easily enable humans or programs to move, colour, texture, animate etc
|
|
one part, for example one wheel of the complete model.
|
|
<li>Hierarchie - You not only have sub objects, but there is a parent-kid relation between some,
|
|
for example, the upper arm of a human model may be "under" the body and the lower arm "under" the upper arm etc.
|
|
<li>DAG - direct acyclic graph means that the hierarchie may not only be a tree where
|
|
each node has exactly one parent (apart from the root, which has zero parents), but that nodes may have more than one parent.
|
|
Used for example in cars to have the wheel geometry only once. If the one wheel-node has four parents, this means
|
|
it will be rendered four times when the scene is drawn.
|
|
<li>Colours - Things can have a colour. Uncoloured objects are always white.
|
|
<li>Textures - Texture things with 2D bitmaps.
|
|
<li>Texture coordinates - The texture mapping is arbitrary.
|
|
<li>Texture coord. per face AND vertex - If a vertex is part of three faces, then this feature
|
|
allows it to have three texture coordinates. For example, a cube may have 18 texture coordinates, even if it has much fewer vertices.
|
|
<li>Texture per face - each face may have another texture bitmap. Formats (and the ssg lib) that
|
|
don't have this have to increase the number of nodes to get this effect.
|
|
<li>Transparency - Some polys may be partially or completely transparent.
|
|
<li>Animation - There may be many different sorts of animation.
|
|
<li>Billboards - geometry that automatically rotates so it always faces the viewer. Normaly flat.
|
|
As an example, can be used to model trees in a driving simulator.
|
|
<li>LOD - stands for "Level of Detail" and means there can be geometries of varying
|
|
complexity for the model, so for example, if it is near the viewer you use many polys
|
|
and if it is far away you use few polys so that the impact on rendering speed is low.
|
|
<li>Other switches - switch means you can switch the visibility of some nodes on and off.
|
|
<li>Ascii or Binary - A stands for Ascii, B for Binary files.
|
|
</ul>
|
|
|
|
<table width="100%" border="1" cellspacing="0" cellpadding="0">
|
|
<tr>
|
|
<td> Feature</td>
|
|
<td> 3DS<BR>load</td>
|
|
<td> AC<BR>load/<BR>save</td>
|
|
<td> ASC<BR>save</td>
|
|
<td> ASE<BR>load/<BR>save</td>
|
|
<td> ATG<BR>load/<BR>save</td>
|
|
<td> DXF<BR>load</td>
|
|
<td> DXF<BR>save</td>
|
|
<td> FLT<BR>load</td>
|
|
<td> M<BR>load/<BR>save</td>
|
|
<td> MD2<BR>load</td>
|
|
<td> OBJ<BR>load</td>
|
|
<td> OBJ<BR>save</td>
|
|
<td> OFF<BR>load/<BR>save</td>
|
|
<td> SSG<BR>load/<BR>save</td>
|
|
<td> Strip<BR>load</td>
|
|
<td> TRI<BR>load/<BR>save</td>
|
|
<td> X<BR>load</td>
|
|
<td> IV<BR>load</td>
|
|
<td> VRML1<BR>load</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Filled polys</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E(5)</td>
|
|
<td> E</td>
|
|
<td> E/D</td>
|
|
<td> ?</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> # sides</td>
|
|
<td> </td>
|
|
<td> n/3</td>
|
|
<td> 3</td>
|
|
<td> 3</td>
|
|
<td> n</td>
|
|
<td> 3,4(4)</td>
|
|
<td> 3</td>
|
|
<td> n</td>
|
|
<td> </td>
|
|
<td> </td>
|
|
<td> n?</td>
|
|
<td> 3</td>
|
|
<td> n</td>
|
|
<td> n(4)</td>
|
|
<td> </td>
|
|
<td> 3?</td>
|
|
<td> n</td>
|
|
<td> 3,4</td>
|
|
<td> 3,4</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Lines</td>
|
|
<td> A</td>
|
|
<td> D/C</td>
|
|
<td> C</td>
|
|
<td> E</td>
|
|
<td> A(?)</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A?</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> B</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Points</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> C</td>
|
|
<td> A(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> B</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Sub objects</td>
|
|
<td> E</td>
|
|
<td> E/D</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> C-D</td>
|
|
<td> C-D</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Hierarchie</td>
|
|
<td> A</td>
|
|
<td> E/D</td>
|
|
<td> E?</td>
|
|
<td> E</td>
|
|
<td> A(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> C</td>
|
|
<td> C</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> C</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> DAG</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A(?)</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Colours</td>
|
|
<td> E</td>
|
|
<td> E/D</td>
|
|
<td> E?</td>
|
|
<td> E</td>
|
|
<td> ?</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> D(1)</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> D</td>
|
|
<td> C</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> B</td>
|
|
<td> B</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Textures</td>
|
|
<td> D</td>
|
|
<td> E/D</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> D</td>
|
|
<td> C</td>
|
|
<td> B</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Texture coord.</td>
|
|
<td> D</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> E</td>
|
|
<td> C</td>
|
|
<td> B</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Texture coord.<BR>per face<BR>AND vertex</td>
|
|
<td> D(?)</td>
|
|
<td> D(?)</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> E</td>
|
|
<td> C</td>
|
|
<td> B(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> C</td>
|
|
<td> E</td>
|
|
<td> E</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Texture per face</td>
|
|
<td> </td>
|
|
<td> D(?)/-</td>
|
|
<td> C</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> B(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> C</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Transparency</td>
|
|
<td> D</td>
|
|
<td> D</td>
|
|
<td> D</td>
|
|
<td> D</td>
|
|
<td> A(?)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A?</td>
|
|
<td> A?</td>
|
|
<td> B(?)</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> E</td>
|
|
<td> B</td>
|
|
<td> B</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Animation</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> B(2)</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A?</td>
|
|
<td> A?</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> B or C</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Billboards</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
</tr>
|
|
<tr>
|
|
<td> LOD</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> B</td>
|
|
</tr>
|
|
<tr>
|
|
<td> Other switches</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> D</td>
|
|
<td> A</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> E</td>
|
|
<td> A</td>
|
|
<td> </td>
|
|
<td> A</td>
|
|
<td> D</td>
|
|
<td> D</td>
|
|
</tr>
|
|
<tr>
|
|
<td> A=Ascii or<BR>B=Binary</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
<td> B</td>
|
|
<td> ?</td>
|
|
<td> A</td>
|
|
<td> A+B(3)</td>
|
|
<td> A</td>
|
|
<td> A</td>
|
|
</tr>
|
|
</table>
|
|
footnotes:
|
|
<BR><BR>
|
|
(1) problematic for ancient files
|
|
<BR>
|
|
(2) DOFs are not implemented
|
|
<BR>
|
|
(3) There is an ascii- and a binary X-file-format.
|
|
I only implemented the ascii-one and probably wont implement the
|
|
binary one. There is a free (as in beer) converter by Microsoft
|
|
running under Windo$.
|
|
<BR>
|
|
(4) It is possible to have polys with an arbitrary number of vertices in ssg.
|
|
But then you may only use one poly per node. Also, you can not mix 3 and 4 sided polys in one node.
|
|
<BR>
|
|
(5) Some OpenGL modes, like for example Quads, are ignored. This means some parts of the model
|
|
may dissappear when saving into DXF files.
|
|
<BR><BR>
|
|
Additional info on some formats:
|
|
|
|
<BR><BR>
|
|
ATG:
|
|
<BR>
|
|
ATG stands for ascii TerraGear. Loading of TriStrips and TriFans not implemented yet.
|
|
Untextured parts are lost, for example when you save and load
|
|
Steve Bakers Tuxedo, you will loose the feet, since they are not
|
|
textured.
|
|
The files written are not optimal, they use no strips/fans,
|
|
only have triangles etc.
|
|
Also, one vertex that needs several texture coords is written out several
|
|
times.
|
|
|
|
|
|
<BR><BR>
|
|
3ds-writer:
|
|
<BR>
|
|
I (Per) have one basicly working, but since there seems to be so much else to do
|
|
with plib right now, I'm a bit reluctant to put my energy into it. Also, the
|
|
only 3ds-loader I've tested files written by it with is the one in ssg :-)
|
|
|
|
|
|
<BR><BR>
|
|
OFF loader:
|
|
<BR>
|
|
Warning: There are two formats called OFF! We support the OFF from GeomView,
|
|
not the one from DEC.
|
|
We support 2D and 3D, but no higher dimensions.
|
|
|
|
<BR><BR>
|
|
.SSG file loader/writer:
|
|
<BR>
|
|
We number .SSG file formats so that for example the loaders knows
|
|
what to expect. Until now, there is
|
|
<BR>
|
|
format "0" - Used by plib 1.2.0, 1.3.x
|
|
<BR>
|
|
format "1" - Will be used by 1.4.0
|
|
<BR>
|
|
Currently, we are between "0" and "1". Normally, we want to keep at least our loader
|
|
compatible, but the changes from zero to one would bloat the code so much and it seems
|
|
.SSG file version zero were only used by people for temporary files, so we decided to make an incompatible break.
|
|
If you need to read or write version zero, either get plib from SVN with the date 14.1.2001, or, if you are a Windo$ person, get
|
|
<a href="prettypoly.sourceforge.net/download/ppewinbin_ssg_version_zero.zip">prettypoly.sourceforge.net/download/ppewinbin_ssg_version_zero.zip</a>
|
|
This allows you to save and load .ssg version zero.
|
|
<BR>
|
|
One of the new features in format "1" might be worth mentioning.
|
|
It is now possible to load and save *any* class derived from ssgBase (notably
|
|
the ssgAux node types).
|
|
All that is needed for saving to work is an implementation of the virtual save() method.
|
|
Loading requires the corresponing load() method, and also means for creating
|
|
an instance of the class, which is accomplished
|
|
by a call to ssgRegisterType().
|
|
See the ssgAux implementation for example usage;
|
|
the convenience function ssgaInit() registers the ssgAux classes.
|
|
<BR><BR>
|
|
.X file writer:
|
|
<BR>
|
|
Planned.
|
|
<BR><BR>
|
|
.X file loader:
|
|
<BR>
|
|
The .X-entity "Frame" is not yet implemented.
|
|
If you convert files into .X with "3D Exploration", you can check the
|
|
option "without frames".
|
|
|
|
<BR><BR>
|
|
VRML1/IV file loaders:
|
|
<BR>
|
|
These are only partially implemented, and are useful primarily for
|
|
mesh-based models (textured or untextured). It would be useful to add
|
|
material support to these loaders, as well as explicit normal definition.
|
|
|
|
<hr>
|
|
<table width="100%">
|
|
<tr>
|
|
<td width="33%" align="left"><a href="ssgContext.html"><= previous =</a></td>
|
|
<td width="34%" align="center"><a href="index.html">Return to SSG Index</a></td>
|
|
<td width="33%" align="right"><a href="LoaderWriter.html">= next =></a></td>
|
|
</tr>
|
|
</table>
|
|
<hr>
|
|
<table>
|
|
<tr>
|
|
<td>
|
|
<a href="http://validator.w3.org/check/referer"><img border="0" src="../valid-html40.png" alt="Valid HTML 4.0!" height="31" width="88"></a>
|
|
<td>
|
|
<ADDRESS>
|
|
<A HREF="http://www.sjbaker.org">
|
|
Steve J. Baker.</A>
|
|
<<A HREF="mailto:sjbaker1@airmail.net">sjbaker1@airmail.net</A>>
|
|
</ADDRESS>
|
|
</table>
|
|
</BODY>
|
|
</HTML>
|
|
|