Hi,
   I rendered a spherical texture for an OpenGL program, I wanted to see 
if the perspective would be all right when applied to a sphere in OpenGL.

The povray object is a cube with cylinders at the edges.

You can see that the perspective is pretty right, since the 3 lines are 
straight (jaggy but straight).

As for the jaggyness, this is due to the fact that the image is placed 
on many triangles which deform the texture to make it fit...

To get rid of the jaggyness I have 3 choices:
   -Pre-deform the texture so it looks correct when deformed (This is 
probably the most stupid way)
   -Add a whole lot more polygons until we can't see the deformation 
(This would be a good idea but would take a lot of time to render)
   -Try Rohan Bernett's idea to map the SkySphere texture on a cube.
I will try the latter...


First image is a sphere mapped with my skysphere texture in POV-Ray.
Second image is a sphere mapped with my skysphere texture in OpenGL.
Note that angles of camera differ...

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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Attachments:
Download 'pov-skysphere.jpg' (22 KB) Download 'gl-skysphere.jpg' (50 KB)

Preview of image 'pov-skysphere.jpg'

Preview of image 'gl-skysphere.jpg'

Here are snapshots of my school project, where I used this exact same
technique.
  The first image is the actual environment map rendered with POV-Ray.
The next four images are snapshots from the OpenGL program.

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Attachments:
Download 'environment.jpg' (28 KB) Download 'snap1.jpg' (20 KB) Download 'snap2.jpg' (26 KB) Download 'snap3.jpg' (23 KB) Download 'snap4.jpg' (24 KB)

Preview of image 'environment.jpg'

Preview of image 'snap1.jpg'

Preview of image 'snap2.jpg'

Preview of image 'snap3.jpg'

Preview of image 'snap4.jpg'

Warp wrote:
> 
>   Here are snapshots of my school project, where I used this exact same
> technique.
>   The first image is the actual environment map rendered with POV-Ray.
> The next four images are snapshots from the OpenGL program.

I suppose your system does not use high dynamic range image data.  In this
situation this would be a good idea (not sure if and how this could be
handled in OpenGL though).

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 28 Feb. 2003 _____./\/^>_*_<^\/\.______

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Christoph Hormann <chr### [at] gmxde> wrote:
> I suppose your system does not use high dynamic range image data.  In this
> situation this would be a good idea (not sure if and how this could be
> handled in OpenGL though).

  I don't understand what would be the use.
  AFAIK HDRI data have only effect on reflections and global illumination.
No such things are used in the OpenGL program. When you look directly
to an unmodified HDRI image, you don't see any difference between it
and a regular image, and that's basically what is seen in the OpenGL
program: The environment map itself.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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>   Here are snapshots of my school project, where I used this exact same
> technique.
>   The first image is the actual environment map rendered with POV-Ray.
> The next four images are snapshots from the OpenGL program.

Very...  Impressive!


I've read your code and you seem to have only 16^2 polygons for your 
skySphere, am I right?  Well, I have 10^2, it might explain the 
jaggyness, but I do believe my code is not as optimal as yours! =)

I'm also afraid, I don't understand much of too-much-3D-geometry!  Would 
you let me use the function you wrote in my program, so I can show you 
how I can make its use look much much more intense?

I'm currently writting a little EyeCandy program, it's much like a 
screensaver, and the story goes like this:  Feel the Explorer in the 
Need for Speed!  Two of which are two of the many symbols of a human mind.

Currenlty, I'd say I'm 40% done with this, if I could use your code for 
the skysphere, I would jump to 60%.

Warp, do you agree?

Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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>   I don't understand what would be the use.
>   AFAIK HDRI data have only effect on reflections and global illumination.
> No such things are used in the OpenGL program. When you look directly
> to an unmodified HDRI image, you don't see any difference between it
> and a regular image, and that's basically what is seen in the OpenGL
> program: The environment map itself.
> 

Hey, why don't we build an OpenGL game completely stuffed with povray 
textures! =)

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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Warp wrote:
> 
> [...]
> 
>   I don't understand what would be the use.
>   AFAIK HDRI data have only effect on reflections and global illumination.
> No such things are used in the OpenGL program. When you look directly
> to an unmodified HDRI image, you don't see any difference between it
> and a regular image, and that's basically what is seen in the OpenGL
> program: The environment map itself.

But there is reflection in your OpenGL images - surely faked somehow but
that's not the point.  

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 28 Feb. 2003 _____./\/^>_*_<^\/\.______

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Christoph Hormann <chr### [at] gmxde> wrote:
> But there is reflection in your OpenGL images

  Where?

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Xilo Musimene <xil### [at] hotpopcom> wrote:
> I'm also afraid, I don't understand much of too-much-3D-geometry!  Would 
> you let me use the function you wrote in my program, so I can show you 
> how I can make its use look much much more intense?

  If I didn't want you to use my code, I wouldn't have posted it in the
first place (I would have just said what I did).

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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Warp wrote:
> 
> Christoph Hormann <chr### [at] gmxde> wrote:
> > But there is reflection in your OpenGL images
> 
>   Where?

You mean the water is only the environment map?

In that case view 3 of your OpenGL samples will just look horrible in an
animation...

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 28 Feb. 2003 _____./\/^>_*_<^\/\.______

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"Xilo Musimene" <xil### [at] hotpopcom> schreef in bericht
news:3EC### [at] hotpopcom...
> I've read your code and you seem to have only 16^2 polygons for your
> skySphere, am I right?  Well, I have 10^2, it might explain the
> jaggyness, but I do believe my code is not as optimal as yours! =)

You can get 'perfect' results (without any jaggyness) if you use a skybox
instead of a skysphere.  It's a little bit more complicated to make suitable
skybox-textures, but the results are faster and better.

cu!

--
camera{location-z*3}#macro G(b,e)b+(e-b)*(C/50)#end#macro L(b,e,k,l)#local C=0
;#while(C<50)sphere{G(b,e),.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1
;#end#end L(y-x,y,x,x+y)L(y,-x-y,x+y,y)L(-x-y,-y,y,y+z)L(-y,y,y+z,x+y)L(0,x+y,
<.5,1,.5>,x)L(0,x-y,<.5,1,.5>,x)               // ZK http://www.povplace.be.tf

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> You can get 'perfect' results (without any jaggyness) if you use a skybox
> instead of a skysphere.  It's a little bit more complicated to make suitable
> skybox-textures, but the results are faster and better.

I've been thinking about this and probably I should need to make 6 
images for the skybox, right?  Or should I still use the exact same 
spherical camera I just used...?

Thanks,
   Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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>   If I didn't want you to use my code, I wouldn't have posted it in the
> first place (I would have just said what I did).

Good! =)

   Then you will probably see a new EyeCandy on my website in a week or two!

Thanks!
   Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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"Xilo Musimene" <xil### [at] hotpopcom> schreef in bericht
news:3EC### [at] hotpopcom...
> > You can get 'perfect' results (without any jaggyness) if you use a
skybox
> > instead of a skysphere.  It's a little bit more complicated to make
suitable
> > skybox-textures, but the results are faster and better.
> I've been thinking about this and probably I should need to make 6
> images for the skybox, right?  Or should I still use the exact same
> spherical camera I just used...?

no, a spherical camera won't work (at least, I don't think it will :), you
will have to make 6 perspective-views.
I did it once, maybe it's still available online, let me check :)
It *might* be this: http://sad.studentenweb.org/cg/stad.zip
But I don't know if it is just the source, or if it is compiled, or whatever
:-/

good luck anyway :)

cu!
--
ZK AKA SaD
http://www.povplace.be.tf
"I'm spinning!"

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> no, a spherical camera won't work (at least, I don't think it will :), you
> will have to make 6 perspective-views.
> I did it once, maybe it's still available online, let me check :)
> It *might* be this: http://sad.studentenweb.org/cg/stad.zip
> But I don't know if it is just the source, or if it is compiled, or whatever
> :-/

I found it in your zip file:

     void setSkyBox(GLuint texture,GLfloat helderheid){
         glDisable(GL_LIGHTING);
         glDisable(GL_CULL_FACE);
         glBindTexture(GL_TEXTURE_2D,texture);
         gluLookAt 
(0.0,0.0,0.0,_lookat.getX()-_locatie.getX(),_lookat.getY()-_locatie.getY(),_lookat.getZ()-_locatie.getZ(),_up.getX(),_up.getY(),_up.getZ());
         glColor4f(helderheid*2,helderheid*1.5,helderheid,1.0);
         glBegin(GL_QUADS);
             // Top
             glTexCoord2f(1.0/4.0,1.0/3.0); glVertex3f(-1.0,1.0,-1.0);
             glTexCoord2f(0.0/4.0,1.0/3.0); glVertex3f(1.0,1.0,-1.0);
             glTexCoord2f(0.0/4.0,2.0/3.0); glVertex3f(1.0,1.0,1.0);
             glTexCoord2f(1.0/4.0,2.0/3.0); glVertex3f(-1.0,1.0,1.0);

             //Left
             glTexCoord2f(1.0/4.0,1.0/3.0); glVertex3f(-1.0,1.0,-1.0);
             glTexCoord2f(1.0/4.0,2.0/3.0); glVertex3f(-1.0,1.0,1.0);
             glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
             glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);

             //Right
             glTexCoord2f(4.0/4.0,2.0/3.0); glVertex3f(1.0,1.0,1.0);
             glTexCoord2f(4.0/4.0,1.0/3.0); glVertex3f(1.0,1.0,-1.0);
             glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);
             glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);

             // Far
             glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
             glTexCoord2f(2.0/4.0,3.0/3.0); glVertex3f(-1.0,1.0,1.0);
             glTexCoord2f(3.0/4.0,3.0/3.0); glVertex3f(1.0,1.0,1.0);
             glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);

             // Near
             glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);
             glTexCoord2f(2.0/4.0,0.0/3.0); glVertex3f(-1.0,1.0,-1.0);
             glTexCoord2f(3.0/4.0,0.0/3.0); glVertex3f(1.0,1.0,-1.0);
             glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);

             //Bottom
             glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);
             glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);
             glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);
             glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
         glEnd();
         glColor4f(1.0,1.0,1.0,1.0);
         glEnable(GL_LIGHTING);
         glEnable(GL_CULL_FACE);
         glLoadIdentity();
     }

But I don't really understand what texture you used...  Did you paste 
the six images toghether in one?

Thanks,
   Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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"Xilo Musimene" <xil### [at] hotpopcom> schreef in bericht
news:3EC### [at] hotpopcom...
> I found it in your zip file:
>
>      void setSkyBox(GLuint texture,GLfloat helderheid){
>          glDisable(GL_LIGHTING);
>          glDisable(GL_CULL_FACE);
>          glBindTexture(GL_TEXTURE_2D,texture);
>          gluLookAt
>
(0.0,0.0,0.0,_lookat.getX()-_locatie.getX(),_lookat.getY()-_locatie.getY(),_
lookat.getZ()-_locatie.getZ(),_up.getX(),_up.getY(),_up.getZ());
>          glColor4f(helderheid*2,helderheid*1.5,helderheid,1.0);
>          glBegin(GL_QUADS);
>              // Top
>              glTexCoord2f(1.0/4.0,1.0/3.0); glVertex3f(-1.0,1.0,-1.0);
>              glTexCoord2f(0.0/4.0,1.0/3.0); glVertex3f(1.0,1.0,-1.0);
>              glTexCoord2f(0.0/4.0,2.0/3.0); glVertex3f(1.0,1.0,1.0);
>              glTexCoord2f(1.0/4.0,2.0/3.0); glVertex3f(-1.0,1.0,1.0);
>
>              //Left
>              glTexCoord2f(1.0/4.0,1.0/3.0); glVertex3f(-1.0,1.0,-1.0);
>              glTexCoord2f(1.0/4.0,2.0/3.0); glVertex3f(-1.0,1.0,1.0);
>              glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
>              glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);
>
>              //Right
>              glTexCoord2f(4.0/4.0,2.0/3.0); glVertex3f(1.0,1.0,1.0);
>              glTexCoord2f(4.0/4.0,1.0/3.0); glVertex3f(1.0,1.0,-1.0);
>              glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);
>              glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);
>
>              // Far
>              glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
>              glTexCoord2f(2.0/4.0,3.0/3.0); glVertex3f(-1.0,1.0,1.0);
>              glTexCoord2f(3.0/4.0,3.0/3.0); glVertex3f(1.0,1.0,1.0);
>              glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);
>
>              // Near
>              glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);
>              glTexCoord2f(2.0/4.0,0.0/3.0); glVertex3f(-1.0,1.0,-1.0);
>              glTexCoord2f(3.0/4.0,0.0/3.0); glVertex3f(1.0,1.0,-1.0);
>              glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);
>
>              //Bottom
>              glTexCoord2f(2.0/4.0,1.0/3.0); glVertex3f(-1.0,-1.0,-1.0);
>              glTexCoord2f(3.0/4.0,1.0/3.0); glVertex3f(1.0,-1.0,-1.0);
>              glTexCoord2f(3.0/4.0,2.0/3.0); glVertex3f(1.0,-1.0,1.0);
>              glTexCoord2f(2.0/4.0,2.0/3.0); glVertex3f(-1.0,-1.0,1.0);
>          glEnd();
>          glColor4f(1.0,1.0,1.0,1.0);
>          glEnable(GL_LIGHTING);
>          glEnable(GL_CULL_FACE);
>          glLoadIdentity();
>      }
>
> But I don't really understand what texture you used...  Did you paste
> the six images toghether in one?

Yes. I used a texture similar to
http://www.turbosquid.com/Previews/Content_on_4_26_2003_07_30_53/1-5-flat.jp
gC46C3EF2-BA1E-444C-ACC051D0AB9AC308.jpgLarge.jpg
I believe the texture I used, is included in the zip, probably skybox.raw (I
believe it's 1024*1024*24bit, RGB, no header).  If it's not included, you
can download it here: http://sad.studentenweb.org/cg/skyboxzonderflare.raw
(3MB!!)

cu!
--
ZK AKA SaD
http://www.povplace.be.tf
"Train you will I. Train you I will. Yes! Step one: touch your tongue to
mine."

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> Yes. I used a texture similar to
> http://www.turbosquid.com/Previews/Content_on_4_26_2003_07_30_53/1-5-flat.jp
> gC46C3EF2-BA1E-444C-ACC051D0AB9AC308.jpgLarge.jpg
> I believe the texture I used, is included in the zip, probably skybox.raw (I
> believe it's 1024*1024*24bit, RGB, no header).  If it's not included, you
> can download it here: http://sad.studentenweb.org/cg/skyboxzonderflare.raw
> (3MB!!)

Ok, now I understand...
But, this takes twice Video RAM as it should...  the white squares are 
also on the VRAM and I think it would be more optimised to use 6 
different square textures...

And I was wondering what exact kind of camera you used?
Simply a normal camera with angle of 90?

Thanks,
   Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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"Xilo Musimene" <xil### [at] hotpopcom> schreef in bericht
news:3EC### [at] hotpopcom...
> Ok, now I understand...
> But, this takes twice Video RAM as it should...  the white squares are
> also on the VRAM and I think it would be more optimised to use 6
> different square textures...

it would probably indeed be more efficient if you used 6 different textures
instead of 1 big, and possibly even easier, but I had to do this very
quickly (school-reasons :) and I didn't think of that :)

> And I was wondering what exact kind of camera you used?
> Simply a normal camera with angle of 90?

I believe so, yes... Let me check! :)
hmm, I don't have the POV-file here, sorry :-/

cu!
--
ZK AKA SaD
http://www.povplace.be.tf
"I won't bite... hard."

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> it would probably indeed be more efficient if you used 6 different textures
> instead of 1 big, and possibly even easier, but I had to do this very
> quickly (school-reasons :) and I didn't think of that :)

Good!

>>And I was wondering what exact kind of camera you used?
>>Simply a normal camera with angle of 90?
> 
> 
> I believe so, yes... Let me check! :)
> hmm, I don't have the POV-file here, sorry :-/

Anyway, it's not a big problem, it's not like if there were thousand 
kinds of cameras!

I'll do some tests whenever I have the time!...

Thanks a lot!
   Xilo

-- 
Dedicated to audio/visual and interactive artwork.
http://www.geocities.com/simonlemieux/

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"Xilo Musimene" <xil### [at] hotpopcom> schreef in bericht
news:3EC### [at] hotpopcom...
> Anyway, it's not a big problem, it's not like if there were thousand
> kinds of cameras!
>
> I'll do some tests whenever I have the time!...

ok, good luck! :)


> Thanks a lot!

np :)

cu!
--
ZK AKA SaD
http://www.povplace.be.tf
"He can breathe OK, long as nobody unplugs him"

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