The kindly Rev. overheard pet### [at] usanet (Peter Popov) saying on
20 Oct 2000: 

>>Yeah, VRML's just a *teensy* bit different from QTVR.  The former is
>>geometry-based, and the latter is photo-based.
>>
>>The only thing that's worth translating at all, imho, is triangle 
>>meshes.  It should be fairly easy with perl or awk or a little piece
>>of C to turn POVRay triangle meshes into VRML IndexedFaceSets.
>
>Doesn't the latest 3DWin read/write from/to Warp's compressed mesh
>format?

Yeah, but I thought Warp's compressed mesh format was also binary 
compressed.  Was I mistaken?  I'm embarrassed to say I haven't looked at 
it yet.

Somehow I have this weird feeling that we're talking about two different 
things.  Please bear with me, on the off chance you don't already know 
this much better than I do.

The .wrl file format is for Virtual Reality Modeling Language (VRML).  
It's a text format (to be specific, UTF8).

The original question was, unless that bad acid is kicking in again, can 
you convert from POVRay to VRML?

Ken answered no, and I agreed with him in the main.  While you do have 
cones, spheres, cylinders, and blocks in both VRML and POVRay, VRML has 
no toruses (or Tauruses), no CSG, no blobs, no computed surfaces, and on 
and on.

But there's two ways to build POVRay scenes: by hand and with a 
modeler.  And since modelers often product lots of triangles and smooth 
triangles, I just wanted to point out that you could, in that subset of 
POVRay scenes, convert a trangle mesh or smooth triangle mesh to a VRML 
IndexedFaceSet, provided you were willing to write a little text 
manipulation program to play around with the text in the POVRay file.  
You could even do it by hand in a text editor if you were far more 
careful and patient than I am.

In the case of triangles, you'd simply take out all the coordinates, 
stick them in an array, and then create coordinate indexes 0 1 2, 3 4 5, 
and so on (in the VRML syntax, each coordIndex ends with a -1 as a 
punctuation mark).

In the case of smooth triangles, you'd take the normal fields and create 
an array of them as well, setting normalPerVertex true.  That ought to 
look pretty good.

But in any case, it's just plain text manipulation, and all the 
information is already there in the .pov or .inc file.  You don't have 
to triangulate or do anything fancy since POV declares one triangle at a 
time.

Now that I think of it, you'd have to change the signs of all the Z 
values.  I'll have to think for a minute about what that means for the 
normals.

If it turns out Warp's compressed format is actually text and lets you 
specify coordinate arrays, coordinate indexes, and indexed arrays of 
vertex or face normals, than I'm the one who doesn't know what's going 
on, and it should be miles easier to convert from that format to VRML.

As to using a cylinder to project an image on in VRML, I've seen it done 
on the Mars Rover images, and it was awful.  You get all the slow 
download speed of bitmap graphics *and* you get crummy looking 
rendering, because VRML has got to project the bits into the viewing 
plane of the browser, which is invariably at the wrong distance and at 
the wrong angle for them to show up very well.  Or will be, as soon as 
the visitor to the VRML world moves.

Now I see what you were talking about when you mentioned projecting the 
scene on a cylinder and using it in QTVR.  If you use SkyPaint 
<http://www.wasabisoft.com/>, you could in fact create a LivePicture 
scene.  I don't know about QTVR itself, though.
-- 
Rev. Bob "Bob" Crispen
crispen at hiwaay dot net

Grabel's Law: 2 is not equal to 3 - not even for very large
values of 2.

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