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Hello
Please help me to find some details about Cylindrical projection.
Thanks.
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"Hamed Ahmadi" <h.a### [at] hotmail com> wrote in message
news:web.472766c1f915cc94f104cee20@news.povray.org...
> Hello
>
> Please help me to find some details about Cylindrical projection.
>
> Thanks.
>
Hi Hamed,
There's a 'cylinder' camera type that you can find in the POV-Ray help file
by searching for 'cylindrical projection' in the index. There are a few
types of projection described there and the 'panoramic' camera type also
gives a form of cylindrical projection.
Also it's possible to project an image (or any other pigment) onto a
cylinder (or indeed onto any other object) using a cylindrical warp. Look
for 'cylindrical warp' in the help where there's an example of using the
cylindrical warp to project a hexagonal pigment onto a cylinder.
Hope that helps. Otherwise, are you able to be a bit more precise about what
you're trying to do?
Regards,
Chris B.
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Thanks for your answer,
actually i'm going to render some 3d models on a cylindrical screen with a
projector and i don't know how to reduce the distotion.
so i'm searching for a way to preduce a distorted screen that looks undistorted
on the cylindrical screen. Could you help me please?
Thanks in advance.
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web.4729d5115849c6ccf104cee20@news.povray.org...
> Thanks for your answer,
>
> actually i'm going to render some 3d models on a cylindrical screen with a
> projector and i don't know how to reduce the distotion.
> so i'm searching for a way to preduce a distorted screen that looks
> undistorted
> on the cylindrical screen. Could you help me please?
>
> Thanks in advance.
>
you could try a cylindrical camera as below.
As you see the scene is very simple : a 1/2 cylinder with a radial pattern.
rendered through a cylindrical camera placed on the axis, the pattern
appears as evenly wide bands.
Is that what you want?
Marc (code below)
#version 3.5;
global_settings {
assumed_gamma 1.0
}
background { color rgb <0.1, 0.3, 0.8> }
// ----------------------------------------
#declare Cylindrical_projection=1;//Set this value to 1 to render a
cylindrical projection
#if (Cylindrical_projection)
// cylinder lens for axis distorted field of view
// 1 is vertical cylinder, fixed viewpoint
// 2 is horizontal cylinder, fixed viewpoint
// 3 is vertical cylinder, viewpoint moves along the cylinder's axis
// 4 is horizontal cylinder, viewpoint moves along the cylinder's axis
camera {
cylinder 1 // types 1, 2 ,3, 4
location <0,0,0> // position
right x*5 // horizontal aspect or field of view
up y*2 // vertical aspect or field of view
look_at <0,0,1> // view
angle 181
}
#else
// perspective (default) camera
camera {
location <2.0, 2.0, -2.0>
look_at <0.0, 0.0, 0.0>
right x*image_width/image_height
}
#end
light_source {
<0, 0, 0> // light's position (translated below)
color rgb <1, 1, 1> // light's color
translate <-10, 30, -30>
}
// ----------------------------------------
#declare Bandes= pigment{
radial frequency 10
color_map {
// [ END_VAL color red R green G blue B filter F transmit T]
[ 0.5 color rgb 0]
[ .5 color rgb 1 ]
// (---alternative form---)
//[ 1.0 color rgbf <0.8, 0.8, 0.8, 1.0> ]
} // color_map
}
intersection{
cylinder{-y,y*1.1,1 texture{ pigment{Bandes}finish {ambient 0 diffuse 0.6}}}
box{<-1,-1.1,0>,<1,1,1> pigment {color rgbt 1}}
no_shadow}
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Hello
as i said before i wanna use a projector and show the scene on a real
cylindrical screen, so i have a question. If i do that with the settings
you mentioned in the previous post, the scene on the screen won't be distorted?
Thanks.
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web.472acbd45849c6ccf104cee20@news.povray.org...
> Hello
>
> as i said before i wanna use a projector and show the scene on a real
> cylindrical screen, so i have a question. If i do that with the settings
> you mentioned in the previous post, the scene on the screen won't be
> distorted?
>
> Thanks.
>
It depends on the lense you use.
May we have some details on the technics involved in this projection?
Marc
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> It depends on the lense you use.
> May we have some details on the technics involved in this projection?
>
> Marc
Dear Marc
I don't have any special technic and i just wanna find a way to have
a undistorted scene on a cylindrical screen with a ordinary projector.
of course I prefer to do that by software modification not by hardware
for example i guess there should be a matrix if i used it in my code (directx)
i will have a undistorted scene, but hardware ways may be used too.
Do you know a special lens for that?
Regards,
Hamed.
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web.472ad84c5849c6ccf104cee20@news.povray.org...
> Dear Marc
>
> I don't have any special technic and i just wanna find a way to have
> a undistorted scene on a cylindrical screen with a ordinary projector.
> of course I prefer to do that by software modification not by hardware
> for example i guess there should be a matrix if i used it in my code
> (directx)
> i will have a undistorted scene, but hardware ways may be used too.
> Do you know a special lens for that?
>
> Regards,
> Hamed.
>
Err I must admit that's beyond my knowledge
Marc
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Thanks anyway,
If you find something even a little, please let me know
you know, i am crazy about the subject.
Best wishes,
Hamed.
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Hamed Ahmadi wrote:
>> It depends on the lense you use.
>> May we have some details on the technics involved in this projection?
>>
>> Marc
>
> Dear Marc
>
> I don't have any special technic and i just wanna find a way to have
> a undistorted scene on a cylindrical screen with a ordinary projector.
> of course I prefer to do that by software modification not by hardware
That's probably not possible. Sure you can find a software
transformation that will compensate the *distortion* (in fact, the
standard POV perspective camera should do it more or less), but your
main problem will be the *focus*. Ordinary projector have lenses
that only produce a sharp image on (or near) a certain plane. The
position of this plane may be adjusted, but it is always a plane.
This means that if your screen is a cylinder, you will have parts of
the screen which are in front of the focus plane and/or other parts
which are behind, and those parts will be out of focus and display a
blurred image.
Jerome
- --
+------------------------- Jerome M. BERGER ---------------------+
| mailto:jeb### [at] freefr | ICQ: 238062172 |
| http://jeberger.free.fr/ | Jabber: jeb### [at] jabberfr |
+---------------------------------+------------------------------+
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