180 degree fov with one single projector

[mue]

Hi!

In the recent past i played around with the idea to get 180 degree field of view with only one single projector. In the following i will describe my thoughts and the outcome.

Projection screen
For the screen there are basically two options:

1) curved screen
2) multiple (three) angled planar screens

I choose the second option, since planar screens are easier to build and the computing and configuration of the necessary image warping (more on this later) seems to be easier too. So I have the following setup:

planar_screens..jpg

Every single screen covers a horizontal field of view (hfov) of 60 degrees, gives me a total fov = 180 degree. The vertical fov (vfov) depends on the height of the screens.

Views
To achieve the correct outside visualization you have to project three adequate views on this screens. Each view with hfov=60 degree and vfov=xx degree. One view in the direction 60 degree left on the left screen, one view straight on on the front screen and one view 60 degree right on the right screen. Note: the visualization is only correct for the viewer if he is located at the sweet-spot.
The three views have to be generated by the simulation software, in my case fs2004. In fs2004 you can display multiple views. The view directions can be configured in panel.cfg and the hfov and vfov can be set by resizing and zooming the view windows. Problem here is that fs2004 doesnt show the values of hfov and vfov.

Projection
For the type of projection there are again two options:

1)front projection
2)rear projection

In front projection the viewer sits between projector and screens. Therefore the projector has to placed high above the viewer. But this is not feasible for me because of room constraints. So I opted for rear projection:

rear_proj..jpg

If you look from the projector position (rear projection) on the angled screens you will see this:

proj_view..jpg

And that's also the image the projector has to project on the angled screens to achieve correct display of the views. (With the difference that the image has to be mirrored because the projector works in rear projection mode.)
In the image above you see the side screens as a (very) smaller area than the front screen. That means fewer pixels can be projected on the side screens. This results in an inferior and darker picture on the side screens than on the front screen. A further problem is that the projector lose focus on the side screens. This compromise I'm willing to accept, since the viewer looks mainly to the front.

Image Warping
The three view windows the simulation software gives me have to be warped and arranged so that the projected views will match the projection screens. The warping and arrangement of the three views are specified by 8 control points (the corners of the screens).

view_warping..jpg

The user has to place the control points at the corners of the screens. The following picture shows the screens and the control points from another perspective.

3d_screens..jpg

For copying, warping and arranging the view windows I wrote a proxy dll that intercepts directx calls. The dll further displays information of hfov and yfov of the view windows. (information I need for resizing and zooming the views to the right parameter to fit my projection screen setup). The proxy dll doesn't need much computing power: In "warping mode" my framerate only drops from 31 fps to 29 fps. Most work is done by the graphic card.


Here is a summery of the steps the user has to take:

-create the three views in fs2004
-resize and zoom the views to get the right hfov and vfov
-placing the 8 control points at the 8 corners of the screens
-activate the warping

I made a video where i try to show this concept. The image quality is bad despite HD resolution. It seems my cam doesn't like the light condition. The rear projection screens are only a test setup. They are made of 25 cm x 25 cm acrylglas with shower curtain on the projector facing side. Because of the acrylglas I get very bad reflections. But I hope you can see that the warping works. Note that the camera was not located at the sweet-spot so the views doesn't look correct (e.g. "horizon breaks" at the screen edges).

Here is the video:

[twisted8]

very interesting! so the dll you wrote can skew the image inside FS?

[Matt Olieman]

Concept is fascinating. Unfortunately, an acceptable resolution to throw a projection of 180 degrees would require quite an expensive projector, more $35,000 ++++. Otherwise you would be looking at a bunch of pixels, particularly the stretched side views.

[mue]

very interesting! so the dll you wrote can skew the image inside FS?

Yes.

Concept is fascinating. Unfortunately, an acceptable resolution to throw a projection of 180 degrees would require quite an expensive projector, more $35,000 ++++. Otherwise you would be looking at a bunch of pixels, particularly the stretched side views.

Yes. You are right. It depends on what one sees as an acceptable resolution. I only have a 1280x720 projector. I still have to test the visualisation in full scale. (Finally, I found appropiate material for my screens: Plexiglas Crystal Ice WM500 SC http://www.plexiglas-shop.com/DE/en/...80n0s34~p.html)
Btw this concept is scaleable: you can made setups with less than 180 degrees fov ,e.g. 135 degrees (3 x 45 degree screens) or 120 degrees (30 degrees for the side screens and 60 degrees for the front screen) or ... as long as fs2004 can create the individual views.

[peter737]

Hello,
can you provide this proxy dll ?
Thank you!

Peter

[fsaviator]

Would this work with a front projection, from above? This is a very interesting effort. Thanks for sharing!

[Rockeyes]

I’m really interested in this and would love to give it a go. Please keep the posts coming.

[mue]

Hello,
can you provide this proxy dll ?
Thank you!

Peter

Yes. But beware! The software is in it's alpha stage: it's not very user friendly and probably has some bugs. Use at your own risk!
The software is written for fs2004 and tested/works on windows xp. On windows xp you only have to copy the proxy dll in the fs 2004 application directory. For inserting a proxy dll on vista and windows 7 you probably have to use some other methods. There are some dll injection tools in the internet. But i don't know if they work with my dll.

Ok, here are the proxy dll for the single projector visualisation. Read the readme.txt for instructions for using the dll.

siprovis.zip

Would this work with a front projection, from above? This is a very interesting effort. Thanks for sharing!

Yes it should work as long as the individual screens are planar.

[mue]

Yesterday I tested my 180 degree fov concept in full scale with three screens each 80x80cm.
Unfortunatly, I'm not so happy with the results:

The side screens are way to dark and the resolution is too low. I thought i can live with that, but the big difference in the image quality between the front screen and the side screens is very distracting. Even a projector with higher resolution can not solve this problem. Maybe in a front projection setup it looks a little bit better.
So I droped the idea of 180 degree fov and changed to 135 degree fov (3 x 45 degree). Here the side screens are not to much angled and the image quality difference between front screen and side screens is smaller.

The next thing i noted is that for proper alignement/warping of the side views i had to place the control points 1 and 7 more in the direction to the center of the side screens. See this image:
set_ctrl_points.jpg
I think it has something to do with the off-axis projection (offset) which most projectors have.
You can place the control points while you are in warping mode. So you can see when the warping looks correct. But beware, the mouse clicks are forwarded to fs2004 and thus the focus of the view windows and thus the order of the view windows can change. If that happens the user has to re-order the view windows.
(See readme.txt in siprovis.zip)

The next feature i'd like to implement is the ability to change the brightness of the individual views, so you can darken the front view that it matches the brightness of the side views.
I'm still experimenting...

[fsaviator]

Thanks for the update. While you're not where you want to be yet, this is great work. Interestingly, I've hads to settle with 135 degrees FOV due to space, so I'm monitoring closely.

Thanks again!

Warren