I have heard about Alpha Bending through a friend, he said he wasn't
sure about the name, but if you've seen the movie Predator it's how he
looked.  It kinda displaced the background and when it stayed still it
was totally transparent, and when it moved, you could tell..  any help
on this would be great, I'm trying to get that texture in Povray if you
can help there also.
Please email me the response since I never go back to news groups, too
many new msgs to sort through you know :-).
                                                               --
Gli### [at] nashvillecom

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Please post replies here to, I'm rather interested...

//Spider

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I was going to start work on a MAX plug-in that did the same thing, only my
C++ is scratchy, so I don't think it's going to develop into anything...

The main thing you have to do is have a depth/bulge map of the distortion.
For instance, white is total strength black is none.  Then you use this and
calculate the pixel offset distance and retreave the pixel from the
background image.  You can also shade this a bit to give it more depth.  The
problem I encountered was which direction to take it from.  I'm going to try
(with a MAX plug-in) to extract the normal channel (the channel which
contains all normal vectors for the image) and use that to get the
direction...

--
Lance.


---
For the latest MAX plug-ins, images and much more, go to:
The Zone - http://come.to/the.zone

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Nick DePalma <Gli### [at] nashvillecom> wrote:
: I have heard about Alpha Bending through a friend, he said he wasn't
: sure about the name, but if you've seen the movie Predator it's how he
: looked.  It kinda displaced the background and when it stayed still it
: was totally transparent, and when it moved, you could tell..  any help
: on this would be great, I'm trying to get that texture in Povray if you
: can help there also.

  There must be a confusion here.
  Alpha blending is the operation you do when you mix two pixels of
different colors with a specific weight (don't know if it's the right term...).
This way you can superimpose a semi-transparent image over another
backgroung image.
  I think that what you are talking about is a displacement map.

: Please email me the response since I never go back to news groups, too
: many new msgs to sort through you know :-).

  Sorry, don't know how to send both article and email from tin...

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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any chance that an object with a refractive index > 1.0 , no
reflections,  no phong, & no absorption could accomplish what you're
looking for?

texture{
   pigment{
      color rgbt <0.0, 0.0, 0.0, 1.0>  // black but compleatly
transparent
      }
   finish{
      reflection 0.0                   // no reflection
      refraction 1                     // refracts light
      ior 1.7                          // index of refraction greater
than air
      }
}

I think it's the effect you're looking for

Steve  (you know the drill, remove the SPAM)

Nick DePalma wrote:
> 
> I have heard about Alpha Bending through a friend, he said he wasn't
> sure about the name, but if you've seen the movie Predator it's how he
> looked.  It kinda displaced the background and when it stayed still it
> was totally transparent, and when it moved, you could tell..  any help
> on this would be great, I'm trying to get that texture in Povray if you
> can help there also.
> Please email me the response since I never go back to news groups, too
> many new msgs to sort through you know :-).
>                                                                --
> Gli### [at] nashvillecom

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No, you're talking about Alpha *Blending*, we're talking about Alpha
*Bending*.  You've got the right idea on the blending, but bending (note the
lack of the "l"), or alpha distortion is a totally different story.

Lance.

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Steve Vogel wrote:
> 
> any chance that an object with a refractive index > 1.0 , no
> reflections,  no phong, & no absorption could accomplish what you're
> looking for?
> 
> texture{
>    pigment{
>       color rgbt <0.0, 0.0, 0.0, 1.0>  // black but compleatly
> transparent
>       }
>    finish{
>       reflection 0.0                   // no reflection
>       refraction 1                     // refracts light
>       ior 1.7                          // index of refraction greater
> than air
>       }
> }
> 
> I think it's the effect you're looking for
> 
> Steve  (you know the drill, remove the SPAM)
<..>

Good start, but if I remember the Predator right, one should model the
ior velocity-dependant. something like
   ior 1+speed
If that should be per body-part or complete is out of the scope of my
memory. Or up to your fantasy :-)

Axel

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Lance Birch <zon### [at] satcomnetau> wrote:
: No, you're talking about Alpha *Blending*, we're talking about Alpha
: *Bending*.  You've got the right idea on the blending, but bending (note the
: lack of the "l"), or alpha distortion is a totally different story.

  Oh, sorry. I should learn to read...

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/

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Axel Hecht wrote:
> 
> Steve Vogel wrote:
> >
> > any chance that an object with a refractive index > 1.0 , no
> > reflections,  no phong, & no absorption could accomplish what you're
> > looking for?
> >
> > texture{
> >    pigment{
> >       color rgbt <0.0, 0.0, 0.0, 1.0>  // black but compleatly
> > transparent
> >       }
> >    finish{
> >       reflection 0.0                   // no reflection
> >       refraction 1                     // refracts light
> >       ior 1.7                          // index of refraction greater
> > than air
> >       }
> > }
> >
> > I think it's the effect you're looking for
> >
> > Steve  (you know the drill, remove the SPAM)
> <..>
> 
> Good start, but if I remember the Predator right, one should model the
> ior velocity-dependant. something like
>    ior 1+speed
> If that should be per body-part or complete is out of the scope of my
> memory. Or up to your fantasy :-)
> 
> Axel

I don't think the Predator effect was actually motion dependant.  It's
just easier to see that type of distortion if it's moving.

PoD.

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Axel Hecht wrote:
>Steve Vogel wrote:
>>
>> any chance that an object with a refractive index > 1.0 , no
>> reflections,  no phong, & no absorption could accomplish what you're
>> looking for?
>>
<SNIP>
>>
>> Steve  (you know the drill, remove the SPAM)
><..>
>
>Good start, but if I remember the Predator right, one should model the
>ior velocity-dependant. something like
>   ior 1+speed
>If that should be per body-part or complete is out of the scope of my
>memory. Or up to your fantasy :-)
>
>Axel

I think the model actually had ior also when it didn't move, it
was just hard to catch sight of. One couldn't see the little
distortion of the jungle behind. Well, at least that's how I
remember it.

Rune S. Johansen
http://hjem.get2net.dk/rsj

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