Kenneth nous apporta ses lumieres en ce 11/04/2006 03:20:
> "Bob H" <omniverse@charter%net> wrote:
> 
>>I've been sitting here looking this over a while now, trying to figure what
>>it does, and finally rendered something to check it out here.
>>
>>...I also multiplied a color_map gradient
>>z to get the fading out effect, as was suggested.
>>
> 
> 
> Congrats on accomplishing that so quickly; you beat me to it!  Not being
> very wise in the way of math functions, I had to slog through a fair amount
> of trial-and-error, discarding one attempt after another, before coming up
> with a fade-out technique that worked well and looked good. Since the
> medias are so dense, I needed a way to fade them out exponentially. Here's
> my final result:
> 
> Create another pigment function:
> #declare my_function_3 =
> function{
>  pigment{
>   gradient z
>   color_map{
>    [0.0 rgb 1]
>    [1.0 rgb 0]
>           }
>      }
>      }
> 
> Then use this in each of the four medias the same way, multiplying the
> original function in each media by this one.  Like this...
> 
> for the absorbing media...
> 
> density{
>  function{
>   my_image_function_1(x,y,z).gray
>   * my_function_3(x,y,pow(z,.07)).gray
>                      }
>            }
> 
> and for each emitting media...
> 
> density{
>  function{
>   my_image_function_2(x,y,z).red // and green, and blue
>   * my_function_3(x,y,pow(z,.07)).gray
>                       }
>             }
> 
> 
> Play around with pow(z,.07) to see the varying fade-out effect.
> 
> BTW, I got rid of the "extra" dino image on the rear of the box by using
> 
> interior_texture{pigment{color rgbt 1}}
> 
> Not ideal, but it does the job. Interior textures can behave strangely,
> depending on where the camera AND the lights are positioned. If the camera
> is moved around behind the box, then suddenly the box's REAR dino image is
> visible and the front one isn't. And it creates a bit of havoc with light
> sources, too. With the camera in the front (the -z direction) and a light
> positioned behind the box, the "invisible" rear-face image casts no shadow.
>  But if the light is also moved in front of that rear face, suddenly it DOES
> cast a shadow...even though the rear image itself is not visible from the
> front. The interior_texture doesn't actually ELIMINATE that rear-face image
> (which is still on the "outside" surface of the box); it just "hides" it
> from the camera and lights--depending on where THEY are.
> 
> Ken
> 
> 
> 
> ------------------------------------------------------------------------
> 
Have you tried cuting a slice off the box with another with an rgbt 1 pigment?
Enlarge the actual box toward the back, make a second shalow box a bit taler and
whider, and 
difference it from the first.
This way, it will make the back of the box it's texture: pigment{rgbt 1}

-- 
Alain
-------------------------------------------------
Gravity is a Myth.  The Earth Sucks!

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