"Kenneth" <kdw### [at] gmailcom> wrote:
> "MichaelJF" <mi-### [at] t-onlinede> wrote:
>
> >
> > My first thought was to have a bigger container and multiple translated
> > densities within the media-statement, but the result was annoying too. A close
> > container seems to be necessary. I then merged the Containers and put multiple
> > densities inside (translated alike the containing boxes). May be more to the
> > intent of omniverse - and no scaling needed.
> >
>
> I ran MichaelJF's code example with one of the latest 64-bit 3.7.1 dev builds
> (v3.7.1-alpha.8927145+av352), with and without the enclosing hollow box.
>
> Without the box, I see NO speckles at all, even during an animation with the
> camear moving around. *With* the enclosing box, the speckles appear, as noted.
> But I tried something else-- eliminating that hollow box, and substituting a
> simple thin background box *behind* the scene instead-- just as a large
> background object. With that box in the scene, the speckles are still there. But
> *without* the box, no speckles. (I actually animated the box to get smaller--
> and as the edges of the box 'pass' the individual speckles (from the camera's
> view), they disappear one by one.)
>
> From this simple test, it *seems* that the speckles only appear when there is
> some kind of background surface behind the scene's media containers. I don't
> know if this helps with the problem, but it's interesting.
>
> By the way: In one of the code examples in this post, the camera is like this:
>
> camera {
>  location -4*x look_at 0
>  up y
>  right image_width/image_height*z // z instead of x
> }
>
> I assumed this was just another way of expressing 'handed-ness' in POV-Ray; but
> the results (compared to *x) are not what I expected; it actually creates a
> flipped mirror-image of the scene, left-to-right. (I tried this with a 'text'
> object, and the text is 'backwards.') I've never used *z there before, so I
> really don't know the reason for this.
>
> But here's the test scene, re-done, to show the speckles problem. Either run a
> 150-frame animation (clock 0 to 1), or just eliminate the background box, to see
> the difference.
>
> -----------
> #version 3.7; // or 3.71
>
> camera {
>  location -4*x look_at 0
>  up y
>  right image_width/image_height*z // should be *x
> }
>
> // background box
> box{<0,-12 + 11.5*clock,-12 + 11.5*clock>,<.1,12 - 11.5*clock,12 -11.5*clock>
>     translate 20*x
>     texture{pigment{rgb .03} finish{ambient 1 diffuse 0}}}
>
> #declare Media_Cont = merge {
>    #for(It,0,1,1) // create multiple boxes
>       box { -1,1
>          rotate <30,30,30>*It
>          translate -<1,1,1>*It/2+<1,1,1>*It/2
>       }
>    #end
>
>    hollow on
> }
> object { Media_Cont
>    pigment {
>       rgbt 1
>    }
>    interior {
>       media {
>          emission <0.1,0.1,0.8>
>          #for(It,0,1,1) // create multiple densities according to the boxes
>             density {
>                boxed
>                density_map {
>                   [0 rgb 1] [0.1 rgb 0] [1 rgb 0]
>                }
>                rotate <30,30,30>*It // same transforms as for the
>                // merged boxes above
>                translate -<1,1,1>*It/2+<1,1,1>*It/2
>             }
>          #end
>       }
>    }
> }
>
> // text objects to show the 'mirror-image' behavior of the
> // camera as-is
> text {
>   ttf "timrom.ttf" "POV-Ray" .01, 0
>   texture{pigment {rgb <.4,1,.4>} finish{ambient 1 diffuse 0}}
>   rotate 90*x
>   translate -1.8*y
>   }
>
> text {
>   ttf "timrom.ttf" "POV-Ray" .01, 0
>   texture{pigment {rgb <1,.4,.4>} finish{ambient 1 diffuse 0}}
>   rotate 90*x
>   translate -1.8*y
>   translate 1.5*z
>   }

I did a low rez 320X240 animation first time and missed the speckles that way,
however 640X480 shows them then disappear as you described.

That scene "container" box was for the potential purpose of adding a color
pattern later, and just to reduce the chances of infinite rays causing problems
(gee, I was wrong about that!); but I think I was seeing some bright specks when
using background{} instead. That could have been from other shapes (torus,
sphere) and not boxes, I forget now.

Maybe Michael is in a mirror world?  :)
I never thought of z as being anything other than near or far, and up or down.
Hadn't considered it for left or 'right'.

Bob

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