gdalgorithms-list

[Algorithms] Lightmap Terrain

[<sro...@te...>]

Hi!

I trying to find how to generate a lightmap/illumination/shadow on a
terrain.
Do you know some good tutorial/code/links talking about that?

I want something to generate a lightmap on a (1025x1025 terrain). A good
generation
if possible like compute the the light from a point. I want generate the
lightmap
just before the use of the terrain and i dont want something that i need to
pre-calculate and put the result on a file or something like.

Thanks,
Corrosif

RE: [Algorithms] OpenGL LockArrayEXT ... workaround

[Ignacio C. <i6...@ho...>]

Maik Gerth wrote:
> yup ... thats what i mean ...
> but what do i do if my vertex array is tooo big?
>
> an unaccelerated vertex array is way too slow in compare to the accelerated
> version ...
> I get a performance increase of 30 % using LockArrayEXT ...
> without it ... vertex arrays are not even a real improvement to im-opengl
>
> so i guess there is no other way than splitting the vertex array : (?

Splitting the your vertex arrays just before locking them can be very tedious, since you have test
triangle of the element array, so that no triangle get splitted and no index references a vertex of
the wrong buffer. It's much easier to do that in an early stage of the rendering pipeline, for
example, for curves it's easy to split them at tesselation time so that the number of vertexes keeps
lower than your desired number. You could also build your characters and objects using different
meshes, instead of a single one.

For gf cards the best workaround for that problem is using vertex array ranges to DMA-copy your data
and overcome CVAs restrictions.

however i think this discussions belongs to the OpenGL gamedev list instead to this one.


Ignacio Castano
ca...@cr...

RE: [Algorithms] OpenGL LockArrayEXT ... workaround

[Ignacio C. <i6...@ho...>]

Conor Stokes wrote:
> First of all, that is a vertex limit. Indices are generally unlimited.
> Second of all, that limit is really only the limit at which the extension
> "optimises" the array via locking. Otherwise, its just like calling a normal
> vertex array call.

are you sure 4096 is the maxium size for optimized compiled vertex arrays?
I just though it was 1024, since q3 uses 1K vertex buffers (according to Brian Sharp's conference).


Ignacio Castano
ca...@cr...

RE: [Algorithms] OpenGL LockArrayEXT ... workaround

[Ko, M. <MAN...@ca...>]

You answered your own question.

-----Original Message-----
From: Maik Gerth [mailto:mai...@gm...]
Sent: Thursday, August 24, 2000 10:58 AM
To: gda...@li...
Subject: AW: [Algorithms] OpenGL LockArrayEXT ... workaround


yup ... thats what i mean ...
but what do i do if my vertex array is tooo big?

an unaccelerated vertex array is way too slow in compare to the accelerated
version ...
I get a performance increase of 30 % using LockArrayEXT ...
without it ... vertex arrays are not even a real improvement to im-opengl

so i guess there is no other way than splitting the vertex array : (?

-----Ursprüngliche Nachricht-----
Von: gda...@li...
[mailto:gda...@li...]Im Auftrag von
Conor Stokes
Gesendet: Donnerstag, 24. August 2000 18:01
An: gda...@li...
Betreff: Re: [Algorithms] OpenGL LockArrayEXT ... workaround


> Hi ...
>
> i got a question about glLockArraysEXT in OpenGl ... since its limited to
> 4096 indices i got a problem with my vertex-list ...
>
> my vertex-list contains like 100.000 vertexes ...
> Im drawing stuff with DrawElements ( ... )  using an compiled index-list
for
> every frame (created by an Octree ...)
>
> now how can i handle the 4096 indice-limit of LockArrayEXT without
spliting
> my Vertex-List in THAT little pieces ...
>
> sorry if i didnt explain it enough but i hope ... someone who worked with
> that already can help me
>
First of all, that is a vertex limit. Indices are generally unlimited.
Second of all, that limit is really only the limit at which the extension
"optimises" the array via locking. Otherwise, its just like calling a normal
vertex array call.

Conor Stokes

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AW: [Algorithms] OpenGL LockArrayEXT ... workaround

[Maik G. <mai...@gm...>]

yup ... thats what i mean ...
but what do i do if my vertex array is tooo big?

an unaccelerated vertex array is way too slow in compare to the accelerated
version ...
I get a performance increase of 30 % using LockArrayEXT ...
without it ... vertex arrays are not even a real improvement to im-opengl

so i guess there is no other way than splitting the vertex array : (?

-----Ursprüngliche Nachricht-----
Von: gda...@li...
[mailto:gda...@li...]Im Auftrag von
Conor Stokes
Gesendet: Donnerstag, 24. August 2000 18:01
An: gda...@li...
Betreff: Re: [Algorithms] OpenGL LockArrayEXT ... workaround


> Hi ...
>
> i got a question about glLockArraysEXT in OpenGl ... since its limited to
> 4096 indices i got a problem with my vertex-list ...
>
> my vertex-list contains like 100.000 vertexes ...
> Im drawing stuff with DrawElements ( ... )  using an compiled index-list
for
> every frame (created by an Octree ...)
>
> now how can i handle the 4096 indice-limit of LockArrayEXT without
spliting
> my Vertex-List in THAT little pieces ...
>
> sorry if i didnt explain it enough but i hope ... someone who worked with
> that already can help me
>
First of all, that is a vertex limit. Indices are generally unlimited.
Second of all, that limit is really only the limit at which the extension
"optimises" the array via locking. Otherwise, its just like calling a normal
vertex array call.

Conor Stokes

_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

Re: [Algorithms] OpenGL LockArrayEXT ... workaround

[Conor S. <cs...@tp...>]

> Hi ...
>
> i got a question about glLockArraysEXT in OpenGl ... since its limited to
> 4096 indices i got a problem with my vertex-list ...
>
> my vertex-list contains like 100.000 vertexes ...
> Im drawing stuff with DrawElements ( ... )  using an compiled index-list
for
> every frame (created by an Octree ...)
>
> now how can i handle the 4096 indice-limit of LockArrayEXT without
spliting
> my Vertex-List in THAT little pieces ...
>
> sorry if i didnt explain it enough but i hope ... someone who worked with
> that already can help me
>
First of all, that is a vertex limit. Indices are generally unlimited.
Second of all, that limit is really only the limit at which the extension
"optimises" the array via locking. Otherwise, its just like calling a normal
vertex array call.

Conor Stokes

RE: [Algorithms] rather odd

[Tom H. <to...@3d...>]

At 09:00 PM 8/22/2000, you wrote:

>In that case I'll chip in again and ask for him to take a look at the 
>number of posts in the archives. There only seems to be posts from the 
>past 2 months...

Yes, I've seen the posts. Yes, I realize the archive is busted. Yes, I know 
there are only two months worth of archives and I've promised to get the 
old archives integrated. No I haven't contacted SourceForge about any of 
this yet. I've been swamped with work. At this moment I can't get into the 
admin section .. looks like the web server is having problems. I'll try 
again tomorrow.

Tom

[Algorithms] OpenGL LockArrayEXT ... workaround

[Maik G. <mai...@gm...>]

Hi ...

i got a question about glLockArraysEXT in OpenGl ... since its limited to
4096 indices i got a problem with my vertex-list ...

my vertex-list contains like 100.000 vertexes ...
Im drawing stuff with DrawElements ( ... )  using an compiled index-list for
every frame (created by an Octree ...)

now how can i handle the 4096 indice-limit of LockArrayEXT without spliting
my Vertex-List in THAT little pieces ...

sorry if i didnt explain it enough but i hope ... someone who worked with
that already can help me

bye

Maik

Re: [Algorithms] Hey everybody

[Sam K. <sa...@ip...>]

Welcome to the list, you sure enough came to the right place.. check the
archives for stuff thats been talked about in the past. Oh and don't
whatever you do talk about patents, it'll only get em' started again...



-----Original Message-----
From: Frag_ Daddy <fra...@ho...>
To: gda...@li...
<gda...@li...>
Date: 23 August 2000 11:03 PM
Subject: [Algorithms] Hey everybody


>
>     Hello people, I'm new to this list, but thought I'd say something.
>First, the list was reccomended by Max Gilead, who I guess is also new to
>this list, but I'm not sure.  Let's see.  I'm very interested in gaming
>algorithms, especially those on artificial intelligence, hidden surface
>removal, and well, all of them.  That said, I hope this list is good.
>Anyway, this isn't the best introduction, but I'll say more later.
>
>     Also, I wanted to mention my website.  It's not really that great, but
>rather, something that I put up in my free-time.  I really need to change
>the url, but like I said, it's in my free-time.  Here's the url:
>
>http://shockonline.homestead.com/openglgameprogramming.html
>
>
>
>Mike Weber
>
>
>p.s.  If you reply to this email, I'm going to be gone for two weeks, so
>don't be offended if I don't answer.
>
>_________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
>
>Share information about yourself, create your own public profile at
>http://profiles.msn.com.
>
>_______________________________________________
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>http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

RE: [algorithms] antiportals?occlusion

[Akbar A. <sye...@ea...>]

>Sorry I didn't respond sooner; I've been on extended vacation.
>My apologies for not being about to help.
np,
tom, jason (ati) and a few others where pretty knowledgeable on this topic
("occlusion-detection circuitry") so we got some good feedback on the
technique and what the xbox could be doing.


peace.
akbar A.

"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.


-----Original Message-----
From: Mike Abrash [mailto:mi...@mi...]
Sent: Wednesday, August 23, 2000 4:17 PM
To: 'Akbar A.'; Algorithms List
Subject: RE: [algorithms] antiportals?occlusion


Sorry I didn't respond sooner; I've been on extended vacation.

I wish I could explain all the details, but I put as much into the article
as I could without running afoul of NDAs, and I had to push to get in as
much as I did. My apologies for not being about to help.

Eric, excellent book!
Regards,
Michael

-----Original Message-----
From: Akbar A. [mailto:sye...@ea...]
Sent: Tuesday, July 04, 2000 6:54 AM
To: Algorithms List
Cc: Mike Abrash
Subject: RE: [algorithms] antiportals?occlusion


>though I do wish there was a little more explanation there
well that's what we are waiting for :-) hopefully we will get some
feedback from abrash.
eric' maybe if you release a new edition of you book , the "design and
implemention of the hardware" on the xbox could make a good chapter :-)
hehe.


peace.
akbar A.

"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.


-----Original Message-----
From: Eric Haines [mailto:er...@ac...]
Sent: Tuesday, July 04, 2000 5:45 AM
To: Algorithms List
Subject: Re: [algorithms] antiportals?occlusion


> "There's also occlusion-detection circuitry that can increase fill rate by
> up to 4X; the effect varies depending on whether pixels are occluded when
> they're drawn, but tends to be greatest exactly when it's needed most"

Nice little article, though I do wish there was a little more explanation
there.
On a related note, ATI's announced Radeon has HyperZ, which ATI doesn't go
into
detail about, but from talking with Jason L. Mitchell this is essentially a
nice
trick to save on fill rate, as follows (from our page
http://www.realtimerendering.com/#speed): When rendering a polygon, the
screen
is split into tiles (e.g. 8x8 pixels or similar; ATI doesn't say the exact
size). Before any pixel Z-buffer testing is performed for a polygon and a
tile,
the highest z-value in the tile is compared to the lowest z-value for the
polygon. If the polygon is farther back than the tile's highest value, then
it
cannot be visible and so individual pixel testing can be avoided. ATI claims
a
20% fill-rate performance gain. How ATI tracks the tile's highest z-value
efficiently (i.e. when a new polygon does get rendered, how do you
efficiently
find the new highest z for the entire tile?) is a trade secret at this
point.

Eric



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[Algorithms] Hey everybody

[Frag_ D. <fra...@ho...>]

     Hello people, I'm new to this list, but thought I'd say something.  
First, the list was reccomended by Max Gilead, who I guess is also new to 
this list, but I'm not sure.  Let's see.  I'm very interested in gaming 
algorithms, especially those on artificial intelligence, hidden surface 
removal, and well, all of them.  That said, I hope this list is good.  
Anyway, this isn't the best introduction, but I'll say more later.

     Also, I wanted to mention my website.  It's not really that great, but 
rather, something that I put up in my free-time.  I really need to change 
the url, but like I said, it's in my free-time.  Here's the url:

http://shockonline.homestead.com/openglgameprogramming.html



Mike Weber


p.s.  If you reply to this email, I'm going to be gone for two weeks, so 
don't be offended if I don't answer.

_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

Share information about yourself, create your own public profile at 
http://profiles.msn.com.

Re: [Algorithms] Terminology Questions

[Marcelo A. C. <ca...@ep...>]

www.flipcode.com just published a basic tutorial on the subject 
of voxel renderers. Worth a look. The exact link is:

http://www.flipcode.com/voxtut/


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Marcelo A. Camelo, Eng. <ca...@ep...> - Software Developer
 
Para facilitar a visualizasao em sistemas nao conformantes com a
norma iso-8859, este email nao utiliza caracteres de acentuacao.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=                        

On Wed, 23 Aug 2000, Pai-Hung Chen wrote:

> Hi,
> 
> Could someone briefly explain what is "voxel" and "wavelet" in the context
> of 3D graphics to get me started?
> 
> Thank you,
> 
> Pai-Hung Chen
> 
> 
> 
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 

RE: [Algorithms] Terminology Questions

[Tom F. <to...@mu...>]

www.google.com is a wonderful thing.

http://www.google.com/search?q=cache:www.whatis.com/voxel.htm+voxel&hl=en

http://www.google.com/search?q=cache:www.mathsoft.com/wavelets.html+wavelet&
hl=en

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Pai-Hung Chen [mailto:pa...@ac...]
> Sent: 23 August 2000 20:32
> To: gda...@li...
> Subject: [Algorithms] Terminology Questions
> 
> 
> Hi,
> 
> Could someone briefly explain what is "voxel" and "wavelet" 
> in the context
> of 3D graphics to get me started?
> 
> Thank you,
> 
> Pai-Hung Chen

[Algorithms] Terminology Questions

[Pai-Hung C. <pa...@ac...>]

Hi,

Could someone briefly explain what is "voxel" and "wavelet" in the context
of 3D graphics to get me started?

Thank you,

Pai-Hung Chen

Re: [Algorithms] Geodesic Sphere (explosion)

[Michael S. H. <mic...@ud...>]

I've found it easiest and most convincing just to use a static half-sphere which is billboarded and scaled as the explosion expands.  Since the texture used is typically an alpha texture which represents an object that has its own "light", I don't worry about the normal going a bit whacky.  Combine the scaling with a bit of texture animation and you end up with good looking explosions.

At 03:52 PM 8/23/00, you wrote:
>Can't you just have a mesh of half a circle and scale it? (Or interpolate
>between 2 frames if it would screw up your dynamic lights)
>
>Odin
>----- Original Message -----
>From: "Aldo Spanghero" <al...@ho...>
>To: <gda...@li...>
>Sent: Wednesday, August 23, 2000 3:44 PM
>Subject: RE: [Algorithms] Geodesic Sphere
>
>
>> Hi.
>>
>> An icosahedron would be fine. I will use it to create 3D explosion for my
>> game.
>> Do you know some algoritm to generate an icosahedron?
>>
>> Thank you.
>>
>> And thanks to the other guys for the answers!
>>
>> >
>> >I don't think the geodesic is made of equilateral triangles ... in fact I
>> >believe the only solid of vaguely spherical shape that you can make with
>> >equilateral triangles is the icosahedron (20 tri's)
>> >
>> >Apart from that I can't help, but I'd have thought a quick search on the
>> >web
>> >would throw up several.
>> >
>> >Robert
>>
>> ________________________________________________________________________
>> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>>
>>
>> _______________________________________________
>> GDAlgorithms-list mailing list
>> GDA...@li...
>> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>>
>
>
>_______________________________________________
>GDAlgorithms-list mailing list
>GDA...@li...
>http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list 

Re: [Algorithms] Geodesic Sphere

[Dave E. <eb...@ma...>]

From: "Adam Moravanszky" <amo...@dp...>
> If I understand your explanation correctly (creating a new vertex inside
the
> triangle, then replacing the original edges of the triangles with
different
> ones), this is pretty much what Kobbelt does.  The 1->4 way I had in mind
> was the common tessellation approach of splitting each of the three edges
of
> the original to create 3 new vertices, then adding 3 new edges to form 4
> triangles.

Of course 4 is correct.  This is what my code does that I mentioned in
an earlier post (subdivide inscribed convex polyhedron).  I was thinking
ahead to the first subdivision in my algorithm where I split into 3.

--
Dave Eberly
eb...@ma...
http://www.magic-software.com

Re: [Algorithms] Geodesic Sphere

[Dave E. <eb...@ma...>]

From: "Aldo Spanghero" <al...@ho...>
> Do you know some algoritm to generate an icosahedron?

MgcReal = float
MgcVector3 is struct { float x, y, z }

    const MgcReal fGold = 0.5*(MgcMath::Sqrt(5.0)+1.0);

    unsigned int uiVertexQuantity = 12;
    MgcVector3* akVertex = new MgcVector3[12];
    akVertex[0] = MgcVector3( fGold,  1.0,  0.0 );
    akVertex[1] = MgcVector3(-fGold,  1.0,  0.0 );
    akVertex[2] = MgcVector3( fGold, -1.0,  0.0 );
    akVertex[3] = MgcVector3(-fGold, -1.0,  0.0 );
    akVertex[4] = MgcVector3( 1.0,  0.0,  fGold );
    akVertex[5] = MgcVector3( 1.0,  0.0, -fGold );
    akVertex[6] = MgcVector3(-1.0,  0.0,  fGold );
    akVertex[7] = MgcVector3(-1.0,  0.0, -fGold );
    akVertex[8] = MgcVector3( 0.0,  fGold,  1.0 );
    akVertex[9] = MgcVector3( 0.0, -fGold,  1.0 );
    akVertex[10] = MgcVector3( 0.0,  fGold, -1.0 );
    akVertex[11] = MgcVector3( 0.0, -fGold, -1.0 );

    unsigned int uiTriangleQuantity = 20;
    unsigned int* auiConnect = new unsigned int[3*20];
    auiConnect[ 0] =  0;  auiConnect[ 1] =  8;  auiConnect[ 2] =  4;
    auiConnect[ 3] =  0;  auiConnect[ 4] =  5;  auiConnect[ 5] = 10;
    auiConnect[ 6] =  2;  auiConnect[ 7] =  4;  auiConnect[ 8] =  9;
    auiConnect[ 9] =  2;  auiConnect[10] = 11;  auiConnect[11] =  5;
    auiConnect[12] =  1;  auiConnect[13] =  6;  auiConnect[14] =  8;
    auiConnect[15] =  1;  auiConnect[16] = 10;  auiConnect[17] =  7;
    auiConnect[18] =  3;  auiConnect[19] =  9;  auiConnect[20] =  6;
    auiConnect[21] =  3;  auiConnect[22] =  7;  auiConnect[23] = 11;
    auiConnect[24] =  0;  auiConnect[25] = 10;  auiConnect[26] =  8;
    auiConnect[27] =  1;  auiConnect[28] =  8;  auiConnect[29] = 10;
    auiConnect[30] =  2;  auiConnect[31] =  9;  auiConnect[32] = 11;
    auiConnect[33] =  3;  auiConnect[34] = 11;  auiConnect[35] =  9;
    auiConnect[36] =  4;  auiConnect[37] =  2;  auiConnect[38] =  0;
    auiConnect[39] =  5;  auiConnect[40] =  0;  auiConnect[41] =  2;
    auiConnect[42] =  6;  auiConnect[43] =  1;  auiConnect[44] =  3;
    auiConnect[45] =  7;  auiConnect[46] =  3;  auiConnect[47] =  1;
    auiConnect[48] =  8;  auiConnect[49] =  6;  auiConnect[50] =  4;
    auiConnect[51] =  9;  auiConnect[52] =  4;  auiConnect[53] =  6;
    auiConnect[54] = 10;  auiConnect[55] =  5;  auiConnect[56] =  7;
    auiConnect[57] = 11;  auiConnect[58] =  7;  auiConnect[59] =  5;

--
Dave Eberly
eb...@ma...
http://www.magic-software.com

Re: [Algorithms] Geodesic Sphere

[Odin J. <od...@it...>]

Can't you just have a mesh of half a circle and scale it? (Or interpolate
between 2 frames if it would screw up your dynamic lights)

Odin
----- Original Message -----
From: "Aldo Spanghero" <al...@ho...>
To: <gda...@li...>
Sent: Wednesday, August 23, 2000 3:44 PM
Subject: RE: [Algorithms] Geodesic Sphere


> Hi.
>
> An icosahedron would be fine. I will use it to create 3D explosion for my
> game.
> Do you know some algoritm to generate an icosahedron?
>
> Thank you.
>
> And thanks to the other guys for the answers!
>
> >
> >I don't think the geodesic is made of equilateral triangles ... in fact I
> >believe the only solid of vaguely spherical shape that you can make with
> >equilateral triangles is the icosahedron (20 tri's)
> >
> >Apart from that I can't help, but I'd have thought a quick search on the
> >web
> >would throw up several.
> >
> >Robert
>
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>

RE: [Algorithms] Geodesic Sphere

[Aldo S. <al...@ho...>]

Hi.

An icosahedron would be fine. I will use it to create 3D explosion for my 
game.
Do you know some algoritm to generate an icosahedron?

Thank you.

And thanks to the other guys for the answers!

>
>I don't think the geodesic is made of equilateral triangles ... in fact I
>believe the only solid of vaguely spherical shape that you can make with
>equilateral triangles is the icosahedron (20 tri's)
>
>Apart from that I can't help, but I'd have thought a quick search on the 
>web
>would throw up several.
>
>Robert

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com

Re: [Algorithms] Geodesic Sphere

[Adam M. <amo...@dp...>]

If I understand your explanation correctly (creating a new vertex inside the
triangle, then replacing the original edges of the triangles with different
ones), this is pretty much what Kobbelt does.  The 1->4 way I had in mind
was the common tessellation approach of splitting each of the three edges of
the original to create 3 new vertices, then adding 3 new edges to form 4
triangles.
--
--Adam Moravanszky
http://www.n.ethz.ch/student/adammo

-----Original Message-----
From: Dave Eberly <eb...@ma...>
To: gda...@li...
<gda...@li...>
Date: Wednesday, August 23, 2000 5:23 AM
Subject: Re: [Algorithms] Geodesic Sphere


>From: "Adam Moravanszky" <amo...@dp...>
>> The classic way to subdivide quadruples your number of triangles with
>every
>> step.  You might find Leif Kobbelt's sqrt(3) subdivision paper from this
>> year's siggraph interesting.  While the paper focuses on subdivision
>> surfaces, he describes a method of subdividing which could be applied to
>> arbitrary problems of tessellation.  His approach triples the number of
>> triangles with every step, allowing for finer LOD control.  It is in fact
>> very simple -- I would be surprised if no one was using this scheme
before
>> him.
>
>I thought the 'classic' way replaced each triangle by three triangles?
>I have not seen Kobbelt's paper, so perhaps he is replacing each
>triangle by two?  An algorithm I describe in my game engine book and
>that was implemented for continuous level of detail of surfaces in
>NetImmerse uses a generalization of Peter Lindstrom's terrain
>system.  For an arbitrary triangle mesh you subdivide each triangle
>once by computing its centroid and adding edges from the three
>vertices to the centroid.  Each subtriangle shares a 'hypotenuse'
>(probably an abuse of the word since the subtriangles are not
>necessarily right-angled) with a subtriangle in the originally
>neighboring triangle.  Once you have this correspondence, you
>attempt to subdivide each hypotenuse based on some heuristic
>like curvature (or curvature + screen space metric).  If the
>subdivision is allowed, you replace each triangle sharing the
>hypotenuse with two triangles formed by drawing an edge from
>the vertex opposite the hypotenuse to the 'midpoint' added by
>the subdivision.  Each subtriangle formed has a hypotenuse that
>is the edge opposite the midpoint.
>
>--
>Dave Eberly
>eb...@ma...
>http://www.magic-software.com

Re: [Algorithms] Tangential Curvature of terrain

[Pai-Hung C. <pa...@ac...>]

----- Original Message -----
From: Klaus Hartmann <k_h...@os...>
To: <gda...@li...>
Sent: Tuesday, August 22, 2000 4:34 PM
Subject: Re: [Algorithms] Tangential Curvature of terrain


> Pierre,
>
> I think it's better if you look for yourself, because people tend to show
> the nicest screenshot they can find, and so do I :)
>
> (Win95/98/2K, 108 KB)
> http://www.thecore.de/TheCore/gdhighlands.zip
>
> Some instructions...
>
> First run the program Highlands.exe. It'll then take a while before you
see
> some terrain, because the program needs to generate the height field and
> textures.
> If you have enough video memory, then try to maximize the window now,
> because that looks better... after all you want to judge the quality of
the
> texture, and not of quality of the LOD algorithm. So it doesn't matter if
> things run a bit slower.
> Now press and hold the <4> key, until the status bar at the top reads
"MRes:
> 15". Note, that the status bar will not update while you hold the key, so
> just hold it long enough. Next step is to enable geomorphing by pressing
the
> <g> key once. Now you can walk around (press <h> for help).
>
> Some more info...
> [1] The sample is work-in-progress, so there are a couple of flaws. For
> example, there are situations, where popping occurs, even though
geomorphing
> is enabled. Also, I don't free all memory, so don't use the <r> key too
> much. In addition, the rendering code is slow (the OpenGL specific
pieces).
>
> [2] The terrain is 1025x1025, and the texture is 1024x1024 (divided into
> sixteen 256x256 patches). Thus, there's less than 1 texel per data point.
>
> [3] I didn't use any image files to create the surface texture. It is
> color-based only. In fact there are seven different colors. 3 of these
> colors are green, 2 are sand, and 2 are gray. The noise-like
> ground-structure was done by adding a small random value to he
illumination
> factors.
>
> [4] There are two light sources. The first one is a direct sun-light that
> shines from the east, and the second is an anit-sunlight source that
shines
> from the west. The lighting is sort of bad, and that's why darker places
> look much better than bright places.
>
> [5] There's no additional noise used to break up the transitions between
the
> ecosystems. It's purely based on the height field.
>
> [6] As I said... some places look good, which does not mean all places :)
So
> you'll have to walk a bit, and maybe try a couple of other terrain (see
> help). Most of the time, things look good, if you are not too close to the
> sight (there's no detail mapping or something like that).
>
> Niki
>
> ----- Original Message -----
> From: Pierre Terdiman <p.t...@wa...>
> To: <gda...@li...>
> Sent: Tuesday, August 22, 2000 4:29 PM
> Subject: Re: [Algorithms] Tangential Curvature of terrain
>
>
> > > There are places in my terrain that look almost real, and I could
> further
> > > enhance this by casting shadows.
> >
> > What about a new snapshot...?   :)
> >
> > Pierre
> >
> >
> >
> > _______________________________________________
> > GDAlgorithms-list mailing list
> > GDA...@li...
> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
>
>
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>

RE: [Algorithms] rather odd

[Chris B. <Chr...@ma...>]

In that case I'll chip in again and ask for him to take a look at the number of posts in the archives. There only seems to be posts from the past 2 months...

cb

-----Original Message-----
From: Akbar A. [mailto:sye...@ea...]
Sent: Wednesday, 23 August 2000 1:50 PM
To: gda...@li...
Subject: RE: [Algorithms] rather odd


>Does any one
>know how to contact the list maintainer?
yes,
it's tom, he will get these :)


peace.
akbar A.

"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.


-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of
Pai-Hung Chen
Sent: Tuesday, August 22, 2000 10:32 PM
To: gda...@li...
Subject: Re: [Algorithms] rather odd


RE: [Algorithms] rather oddI've asked for help with list archive some time
ago but got no answer.  I think it returns nothing no matter what word you
submit.  I am desperating for some articles in the archive.  Does any one
know how to contact the list maintainer?

Pai-Hung Chen

----- Original Message -----
From: Chris Brodie
To: 'gda...@li...'
Sent: Tuesday, August 22, 2000 5:24 PM
Subject: RE: [Algorithms] rather odd


I think it just doesn't work. I've been referred to the archives a few times
re my questions on VIPM's. Do a search on VIPM and you get back nothing.
(Apologies for the HTML if you see it. My mail department says your not
getting it :) )
-----Original Message-----
From: Akbar A. [mailto:sye...@ea...]
Sent: Wednesday, 23 August 2000 8:49 AM
To: gda...@li...
Subject: [Algorithms] rather odd
is the search feature of the list broken?
i did a search forbarycentric
and i found nothing.
i am pretty sure that word has been mentioned before ;)
http://www.geocrawler.com/lists/3/SourceForge/4856/0/
peace.
akbar A.
"US4643421: Video game in which a host image repels ravenous images by
serving filled vessels "
http://www.patents.ibm.com/details?&pn10=US04643421
this was a fun game though ;)




_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list


_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list


_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

RE: [Algorithms] rather odd

[Akbar A. <sye...@ea...>]

>Does any one
>know how to contact the list maintainer?
yes,
it's tom, he will get these :)


peace.
akbar A.

"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.


-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of
Pai-Hung Chen
Sent: Tuesday, August 22, 2000 10:32 PM
To: gda...@li...
Subject: Re: [Algorithms] rather odd


RE: [Algorithms] rather oddI've asked for help with list archive some time
ago but got no answer.  I think it returns nothing no matter what word you
submit.  I am desperating for some articles in the archive.  Does any one
know how to contact the list maintainer?

Pai-Hung Chen

----- Original Message -----
From: Chris Brodie
To: 'gda...@li...'
Sent: Tuesday, August 22, 2000 5:24 PM
Subject: RE: [Algorithms] rather odd


I think it just doesn't work. I've been referred to the archives a few times
re my questions on VIPM's. Do a search on VIPM and you get back nothing.
(Apologies for the HTML if you see it. My mail department says your not
getting it :) )
-----Original Message-----
From: Akbar A. [mailto:sye...@ea...]
Sent: Wednesday, 23 August 2000 8:49 AM
To: gda...@li...
Subject: [Algorithms] rather odd
is the search feature of the list broken?
i did a search forbarycentric
and i found nothing.
i am pretty sure that word has been mentioned before ;)
http://www.geocrawler.com/lists/3/SourceForge/4856/0/
peace.
akbar A.
"US4643421: Video game in which a host image repels ravenous images by
serving filled vessels "
http://www.patents.ibm.com/details?&pn10=US04643421
this was a fun game though ;)




_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list


_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

Re: [Algorithms] rather odd

[Pai-Hung C. <pa...@ac...>]

RE: [Algorithms] rather oddI've asked for help with list archive some time
ago but got no answer.  I think it returns nothing no matter what word you
submit.  I am desperating for some articles in the archive.  Does any one
know how to contact the list maintainer?

Pai-Hung Chen

----- Original Message -----
From: Chris Brodie
To: 'gda...@li...'
Sent: Tuesday, August 22, 2000 5:24 PM
Subject: RE: [Algorithms] rather odd


I think it just doesn't work. I've been referred to the archives a few times
re my questions on VIPM's. Do a search on VIPM and you get back nothing.
(Apologies for the HTML if you see it. My mail department says your not
getting it :) )
-----Original Message-----
From: Akbar A. [mailto:sye...@ea...]
Sent: Wednesday, 23 August 2000 8:49 AM
To: gda...@li...
Subject: [Algorithms] rather odd
is the search feature of the list broken?
i did a search forbarycentric
and i found nothing.
i am pretty sure that word has been mentioned before ;)
http://www.geocrawler.com/lists/3/SourceForge/4856/0/
peace.
akbar A.
"US4643421: Video game in which a host image repels ravenous images by
serving filled vessels "
http://www.patents.ibm.com/details?&pn10=US04643421
this was a fun game though ;)




_______________________________________________
GDAlgorithms-list mailing list
GDA...@li...
http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list

Re: [Algorithms] Geodesic Sphere

[Dave E. <eb...@ma...>]

From: "Adam Moravanszky" <amo...@dp...>
> The classic way to subdivide quadruples your number of triangles with
every
> step.  You might find Leif Kobbelt's sqrt(3) subdivision paper from this
> year's siggraph interesting.  While the paper focuses on subdivision
> surfaces, he describes a method of subdividing which could be applied to
> arbitrary problems of tessellation.  His approach triples the number of
> triangles with every step, allowing for finer LOD control.  It is in fact
> very simple -- I would be surprised if no one was using this scheme before
> him.

I thought the 'classic' way replaced each triangle by three triangles?
I have not seen Kobbelt's paper, so perhaps he is replacing each
triangle by two?  An algorithm I describe in my game engine book and
that was implemented for continuous level of detail of surfaces in
NetImmerse uses a generalization of Peter Lindstrom's terrain
system.  For an arbitrary triangle mesh you subdivide each triangle
once by computing its centroid and adding edges from the three
vertices to the centroid.  Each subtriangle shares a 'hypotenuse'
(probably an abuse of the word since the subtriangles are not
necessarily right-angled) with a subtriangle in the originally
neighboring triangle.  Once you have this correspondence, you
attempt to subdivide each hypotenuse based on some heuristic
like curvature (or curvature + screen space metric).  If the
subdivision is allowed, you replace each triangle sharing the
hypotenuse with two triangles formed by drawing an edge from
the vertex opposite the hypotenuse to the 'midpoint' added by
the subdivision.  Each subtriangle formed has a hypotenuse that
is the edge opposite the midpoint.

--
Dave Eberly
eb...@ma...
http://www.magic-software.com