I would like to render an object in POV where the background is an AVI file.
I wrote a program that a.o. can extract the consecutive frames from the
AVI, and I use these images as background by setting them as an image map
on a plane. Things look OK, but the lights disturb these background images,
they become too bright!
BTW: of course I need lights in the POV scene to light my objects.

I hope there is a way to put external images as a background (or backdrop)
into POV scenes without the scene infuencing the image.

Thanks!

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nomail@nomail wrote:
> Things look OK, but the lights disturb these background images,
> they become too bright!

  Theoretically you could use the image in a sky_sphere, which is not
affected in any way by light sources, but it might not be trivial to
transform the image_map so that it will perfectly fill the viewport.

  With the image_map in a plane you could just try setting the finish
of the plane to 'ambient 1'.

-- 
#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 nous apporta ses lumieres ainsi en ce 21/06/2004 13:59... :

>nomail@nomail wrote:
>  
>
>>Things look OK, but the lights disturb these background images,
>>they become too bright!
>>    
>>
>
>  With the image_map in a plane you could just try setting the finish
>of the plane to 'ambient 1'.
>
>  
>
If you go that way, also set 'diffuse 0'. This way, it won't be affected 
by your light.

Alain

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Warp and Alain,

Thanks a lot for your advices! I now have things running the way you
proposed! The only thing that bothers me is the absence of the possibility
to have a background image in stead of background color, so for the time
being I'll have to do it with a plane as background.
What I had to do is to define the plane (with an image of 720 * 576, DV PAL)
in such a way that it fills the resulting POV end image (also 720 * 576), I
did this on an experimental basis, is there an easy rule for this?

Next to that: I developed a VB program that allows images to be superimposed
on AVI footage made by Digital Video camera, where the position of the
image can be locked to a certain objectposition on the AVI. The program
does some image analysis in order to automatically trace the object in the
AVI, so for instance I can place a tree somewhere on the ground and this
tree will stay on it's virtual place no matter the movement of the camera.
(see www.stabilize.tk for a demoversion of this program called VMT). Now I
would like to adjust the program that it also can place animations on the
AVI footage, using POV. In my test this already works! What I do in VMT is
to point at the position where I like to place the POV object. VMT then
traces this position and a.o. outputs a datafile where the X and Y position
of the indicated point. These data then should be used by POV to translate
the object to the correct position of the point in different frames.
The X and Y positions are in DV coordinates (1-720, 1-576). How to best
recalculate these coordinates for the translation?

Thanks in advance for your advice!

Hans

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> Thanks a lot for your advices! I now have things running the way you
> proposed! The only thing that bothers me is the absence of the possibility
> to have a background image in stead of background color, so for the time
> being I'll have to do it with a plane as background.

I'm confused; they suggestions they gave you should not have limited your
ability to use an image.

The original setup that you had, with finish {ambient 1 diffuse 0} should
have worked fine; the image would not be affected by lighting and would be
visible in the background if you placed the plane right.

 - Slime
 [ http://www.slimeland.com/ ]

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Slime, thanks for your reaction; I think I didn't explain my problem
clearly.
Using the plane with an image works fine; my problem however (due to
inexperience probably!) is that everytime I change the camera position I
also have to change the plane's position.
Using a background or even better a backdrop like in Carrara overcomes this
problem. I hope you can give me an advice how to position the plane with
the image file in such a way that it remains visible no matter the camera's
orientation!

regards, Hans

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> Using the plane with an image works fine; my problem however (due to
> inexperience probably!) is that everytime I change the camera position I
> also have to change the plane's position.

Ah.

You may want to look into screen.inc. Specifically, the Screen_Plane macro
may do what you want. Although the macro is intended to put a plane *close*
to the camera, with a large value for "Scaling" (the second argument), I
think you can make it go as far away from the camera as you want.

 - Slime
 [ http://www.slimeland.com/ ]

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Slime,

Looks like this is exactly what I am looking for! Thanks a lot for your
advice!

Hans

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