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I use blue screen.
Make a plane behind it all one color with an ambient of 1, watch out for
reflections, don't use AA, then use your paint tool to make that color
transparent.
Phil Clute <pcl### [at] tiac net> wrote in message
news:37544197.56DAD75B@tiac.net...
> Is there a way to make my background transparent?
> Say for instance I want to render an object and then use the
> image as a layer in Photoshop on top of an actual photo.
> Like me standing next to an X-wing or something. I could
> of course cut out the X-wing but if POV can already do
> transparency I could just layer it.
>
> --
> ...coffee?...yes please! extra sugar,extra cream...Thank you.
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Remco de Korte <rem### [at] xs4allnl> wrote:
> Peter Popov wrote:
>> On 1 Jun 1999 16:39:01 -0500, par### [at] fwicom (Ron Parker) wrote:
>>
>> >Use an image format that supports an alpha channel (PNG
>> >does) and put the +UA switch on the command line or in
>> >your ini file.
>>
>> ...and don't use a sky sphere nor afloor plane.
>
> ... but use background{}.
Actually, you *can* use a sky_sphere, which is nice if you want a
metallic object to reflect the sky. Here's what I did when I wanted
this effect:
#declare P_Cloudy = pigment { bozo // (based on P_Cloud3)
colour_map {
[0.0 rgb <0.850, 0.850, 0.850> ]
[0.1 rgb <0.550, 0.600, 0.650> ]
[0.5 rgb <0.184, 0.184, 0.309> ]
[1.001 rgb <0.100, 0.100, 0.200>]
}
turbulence 0.65 octaves 6 omega 0.707 lambda 2 scale <6,4,6>
}
#declare S_HalfSky = sky_sphere {
pigment { gradient y
pigment_map {
[0.500 rgbt <0.5,0.5,0.5,1>]
[0.500 rgb <0.184, 0.184, 0.309> ]
[0.575 P_Cloudy scale <0.05, 0.40, 0.05> rotate z*30 ]
[0.725 P_Cloudy scale <0.25, 0.15, 0.50> ]
}
translate y*-0.5
scale 2
}
}
This puts clouds in the top half of the sky sphere, but a 50% grey with
full transparency in the bottom half. (I've found that 50% grey works
better than pure black or white when compositing the sprite over a
variety of differently-coloured background images.)
The only caveat I've discovered about creating sprites by this method is
that the alpha channel is derived from the first surface POV-Ray
encounters -- if you have a glass sphere with an opaque object inside
it, the alpha channel will *not* reflect the presence of the opaque
object; the background will show through the opaque object.
month ago, in the povray.bugreports group:
> Here's my solution: I create another scene with the same camera and
> objects. You remove the light_source. And: the background is black,
> the opaque objects are white, and transparent objects vary from
> rgbt<1,1,1,0> (transmit=0 in the original scene) to rgbt<1,1,1,1>
> (transmit=1 in the original scene). Of course, don't forget to set
> finish { ambient 1 diffuse 0 }.
>
> POV-Ray will directly render a 256-gray picture: the alpha channel
> you need.
>
> It works, but it needs more work than automatic alpha-channel
> rendering.
--
Jeff Lee shi### [at] gatenet http://www.gate.net/~shipbrk/
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