|
 |
"Hamed Ahmadi" <h.a### [at] hotmail com> wrote in message
news:web.472ad84c5849c6ccf104cee20@news.povray.org...
>> 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.
>
Hi Hamed,
Just to be sure we're on the same page...
You want to project onto a screen that forms an arc around the projector.
The projector will be level and at the same height as the centre of the
image on the screen. Your projector is a fairly ordinary projector, so will
only send out an image straight ahead, and about 20 degrees left and right,
up and down, so would only put an image on about 12% of a completely
cylindrical screen?
If that's the case then you should be able to use the POV-Ray camera
settings Marc suggested with a little trial and error. You may have
difficulty getting the whole image in focus at the same time. I would
imagine that projectors 'correct' the focus to get a good image on a flat
screen. You'll need to adjust the up and right vectors to match the
projector lens, but you should be able to use the test scene that Marc
posted to 'calibrate' that.
If you don't want the projector to be level and at the centre point of the
cylinder then it becomes a bit more difficult and I think you would probably
need to render in two passes to deal with that properly. For example, if you
want to project down from a ceiling mounted projector or if you want to
project onto the outside of a cylindrical screen. In these cases the problem
of getting the whole image in focus is also likely to be accentuated.
Regards,
Chris B.
Post a reply to this message
|
|
|
|
> If you find something even a little, please let me know
> you know, i am crazy about the subject.
Greetings from Perth, if I understand you correctly you want to create graphics
for a cylindrical display. I have done this for full 360 degree displays
including those that are additionally stereo. What you generally need to do is
twofold
1. Create your content as cylindrical panoramic images, I suggest just panoramic
of the right vertical field of view to match your projection environment. See
more details on the equations see
http://local.wasp.uwa.edu.au/~pbourke/projection/stereopanoramic/procedure/
2. You then need to geometry correct (warp) the images so that when projected
using a (perspective) projector you get the right image on the cylinder. See
http://local.wasp.uwa.edu.au/~pbourke/projection/cylinder/
and
http://local.wasp.uwa.edu.au/~pbourke/projection/cylmapper/
-------------------------------------
P a u l B o u r k e
http://local.wasp.uwa.edu.au/~pbourke/
Post a reply to this message
|
|
|
|
> I had visited the pages and I was interested in them. They seems applicable
specially
> "Image warping for projection onto a cylinder" part,
> but I didn't find any algorithm or detailed information on it. Actually I'm
> just working on image warping.
> Would you give me some detailed algorithms to implement it?
Well, there are lots of possible ways .... since you posted this to the PovRay
group, one way is to render a panoramic image of your scene using PovRay. Then
create a second model that consists of just a cylinder, the same dimensions as
the cylinder you plan to project onto and with your panoramic image applied as
a texture. Create a camera at the same location and of the same specifications
as your data projector. If you render this second scene then you will have the
correctly warped result. Note that since PovRay doesn't readily do offset
frustums then you need to get up to tricks like this to get the offset frustrum
your data projector creates.
http://local.wasp.uwa.edu.au/~pbourke/projection/mirrorrender/
Post a reply to this message
|
|
