Hi,

Is there any general image map tutorial / general strategies on placing
image maps on complicated objects?  I've found it quite difficult making a
transparent .gif, finding the transparent color so the base texture can be
seen, and then scaling and placing the image on the object to make this
"decal" effect look plausible.

Thanks,
-Chris-

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Chris Spencer wrote:

> Hi,
>
> Is there any general image map tutorial / general strategies on placing
> image maps on complicated objects?  I've found it quite difficult making a
> transparent .gif, finding the transparent color so the base texture can be
> seen, and then scaling and placing the image on the object to make this
> "decal" effect look plausible.

Make an orthographic render perpendicular to the image map and use it as a
base to edit the map.

--
___     _______________________________________________
 | \     |_          <dav### [at] faricynet> <ICQ 55354965>
 |_/avid |ontaine        http://www.faricy.net/~davidf/

"The only difference between me and a madman is that I'm not mad." -Dali

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Thanks for the reply, but you lost me.  I searched the POV help file but  I
couldn't find a good description or implementation of an orthographic
camera.  How would this help placing an image map?

-Chris-

> Chris Spencer wrote:
>
> > Hi,
> >
> > Is there any general image map tutorial / general strategies on placing
> > image maps on complicated objects?  I've found it quite difficult making
a
> > transparent .gif, finding the transparent color so the base texture can
be
> > seen, and then scaling and placing the image on the object to make this
> > "decal" effect look plausible.
>
> Make an orthographic render perpendicular to the image map and use it as a
> base to edit the map.

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In article <38e9e4ed$1@news.povray.org>, "Chris Spencer" 
<chr### [at] bluelectrodecom> wrote:

> Thanks for the reply, but you lost me.  I searched the POV help file but  
> I couldn't find a good description or implementation of an 
> orthographic camera.

Section 4.4.2 "Types of Projection", in the manual. Not a real great 
explanation, though. Also look at section 2.4.4.1 "Understanding The 
Concept of Splines". That part of the tutorial has a short "spline 
workshop" scene that includes an example of the orthographic camera.
And check out this demo scene:
POV-Ray:Scenes:camera:camera1b.pov


> How would this help placing an image map?

It doesn't really help in placing one, just in designing one and placing 
the details. Well, it might help get the alignment right...
The idea is you render an image with the orthographic camera, and then 
use that image to place the details on the image map. The image map is 
projected like the orthographic camera by default, so you just have to 
scale/translate it to the same position and size as the camera was.

To make a decal, take a view along one axis with the orthographic 
camera, "paint" on the rendered image, making the overlay, and then 
apply that image as the decal using an image_map.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Web page: http://chrishuff.dhs.org/

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Chris, I never really understood this part: am I correct an assuming that the
width of the view at the look_at point is the same with an orthographic
camera? If not, how do you determine the width of the view?

--
___     _______________________________________________
 | \     |_          <dav### [at] faricynet> <ICQ 55354965>
 |_/avid |ontaine        http://www.faricy.net/~davidf/

"The only difference between me and a madman is that I'm not mad." -Dali

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David Fontaine wrote:
> 
> Chris, I never really understood this part: am I correct an assuming that the
> width of the view at the look_at point is the same with an orthographic
> camera? If not, how do you determine the width of the view?

Hi David.

I think that width and height of the view are determined by the length
of right and up vectors of the camera.

Bouf.

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"David Fontaine" <dav### [at] faricynet> wrote in message
news:38EAB254.324C5E88@faricy.net...
| Chris, I never really understood this part: am I correct an assuming that the
| width of the view at the look_at point is the same with an orthographic
| camera? If not, how do you determine the width of the view?

I just happen to be answering before Chris since I'm online at this time of
morning, so excuse me if I'm interrupting please.
'up' and 'right' define the dimensions of the orthographic view window, centered
on 'look_at' of course.
The good thing about it is you can use what will be your image map resolution
for the values, as in up 300*y right 400*x.
Watch out when positioning the camera so as not to put it right near <0,0,0> as
someone had pointed out a while back here at the newsgroups.  Seems that the
orthographic camera can break down at too small a range from the look_at.  You
should be able to safely put the camera at any typical distance (for
simplicity -10*z and looking to <0,0,0>).
This makes for a kind of hollow bar which runs a length away from the camera yet
stays the same width and height for the entire distance.

Bob

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> > Thanks for the reply, but you lost me.  I searched the POV help file but
> > I couldn't find a good description or implementation of an
> > orthographic camera.
>
> Section 4.4.2 "Types of Projection", in the manual. Not a real great
> explanation, though. Also look at section 2.4.4.1 "Understanding The
> Concept of Splines". That part of the tutorial has a short "spline
> workshop" scene that includes an example of the orthographic camera.
> And check out this demo scene:
> POV-Ray:Scenes:camera:camera1b.pov
>
>
> > How would this help placing an image map?
>
> It doesn't really help in placing one, just in designing one and placing
> the details. Well, it might help get the alignment right...
> The idea is you render an image with the orthographic camera, and then
> use that image to place the details on the image map. The image map is
> projected like the orthographic camera by default, so you just have to
> scale/translate it to the same position and size as the camera was.
>
> To make a decal, take a view along one axis with the orthographic
> camera, "paint" on the rendered image, making the overlay, and then
> apply that image as the decal using an image_map.

Ok, I understand everything up until the the part when I have to
scale/translate the image to the position corresponding to the ortho
camera's position.  Thanks for the help with the camera.

Here's my code, the maped texture is labeled ImagemapTex:

#include "colors.inc"

background { color <1.000,1.000,1.000> }

// lights

light_source {   // Light1
  <200.000, 200.000, 200.000>
  color rgb <1.000, 1.000, 1.000>
}

light_source {   // Light2
  <-10.000, 8.000, 100.000>
  color rgb <1.000, 1.000, 1.000>
}

// camera, side view

  #declare Angle = 30;

  camera {  //  Camera SpotCam001
  // orthographic
  location  < 0,  50, 0>
  sky       < 0,  0,  1> // Use right handed-system
  up        < 0,  0,  1> //< 0,  0,  1*25> //  For orthographic camera
  right     <4/3, 0.0, 0.0> //<4/3*25, 0.0, 0.0> //       For orthographic
camera
  angle         Angle
  look_at   < 0,  0,  0>
        }

// textures

#declare ImagemapTex =
  texture{
    pigment {
      color Blue
      }
    finish{
      ambient 0
     }
    }
  texture{
    pigment{
      image_map{
        png "decal_rombot_nametag01.png" // the file to read
(iff/gif/tga/png/sys)
        map_type 0 // 0=planar, 1=spherical, 2=cylindrical, 5=torus
        interpolate 0 // 0=none, 1=linear, 2=bilinear, 4=normalized distance
        // [filter N V] // N=all or color index # (0...N), V= value
(0.0...1.0)
        // [transmit N V] // N=all or color index # (0...N), V= value
(0.0...1.0)
        // [use_color | use_index]
        once
        // image_map
        }
        // rotate <0,50,0> translate <0,50,0> ??? <--- I think this is where
I need help.
       }
      }

// objects

plane
{
  z, // <X Y Z> unit surface normal, vector points "away from surface"
  -10.0 // distance from the origin in the direction of the surface normal
  texture { pigment { checker color rgb <1.0, 1.0, 1.0> color rgb <0.0, 0.0,
0.0>  }  }
}

sphere
{
  <0, 0, 0> // center of sphere <X Y Z>
  10       // radius of sphere
  scale <1, 1, .75>
  texture {ImagemapTex}
}

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Oh wow, confusing me  :-)
Anyway, all you're really needing is to center the image first then scale it to
the size you have set in the camera.  Since the image starts off as 1 unit
square with lower left corner at <0,0,0> then you want to do 'translate
<-0.5,-0.5,0>'  and then  'scale <25,25,1>' and finally 'rotate 90*x' for the
camera to see it.
That should be it I think.   That plane {z,-10 is not going to show up though.
The camera will be looking parallel along it and therefore see nothing of it.
If I'm understanding this right then you are trying to get a spherical image
which is actually mapped on as planar to be seen orthographically which then no
longer has any spherical quality.  Which is why I got confused.  Anyone else?

Bob

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> Oh wow, confusing me  :-)
> Anyway, all you're really needing is to center the image first then scale
it to
> the size you have set in the camera.  Since the image starts off as 1 unit
> square with lower left corner at <0,0,0> then you want to do 'translate
> <-0.5,-0.5,0>'  and then  'scale <25,25,1>' and finally 'rotate 90*x' for
the
> camera to see it.
> That should be it I think.   That plane {z,-10 is not going to show up
though.
> The camera will be looking parallel along it and therefore see nothing of
it.

That worked out fine.  The checkered plane was there for a later 3D view,
when the ortho camera was commented out.

I tried mapping the image as a spherical type, but it became incredibly
distorted.  Planar seemed the best option and didn't distort much.

Thanks again,

-Chris-

> If I'm understanding this right then you are trying to get a spherical
image
> which is actually mapped on as planar to be seen orthographically which
then no
> longer has any spherical quality.  Which is why I got confused.  Anyone
else?

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