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clipka <ano### [at] anonymousorg> wrote:
> Am 10.01.2018 um 12:18 schrieb Motive17:
> > Simple question:
> >
> > do you know if there is a way for extracting the length of the rays path from
> > the light source until the camera?
>
> If there is only one light source involved, you /could/ use a special
> pigment for the objects in your scene that sums up the distance between
> the surface and the camera plus the distance between the surface and the
> light source.
>
> Use a function-based pigment, with a function constructed like this:
>
> #declare FnDist = function(x,y,z) { sqrt(x*x + y*y + z*z) }
> #declare Fn = function(x,y,z) {
> FnDist(x-xC,y-yC,z-zC) +
> FnDist(x-xL,y-yL,z-zL)
> }
> #declare P = pigment {
> function { Fn(x,y,z)/MaxDistance }
> }
>
> where <xC,yC,zC> is the location of the camera, <xL,yL,zL> is the
> location of the light source, and MaxDistance is the maximum total
> distance you want to be able to handle properly.
>
> Then choose a finish that gives full brightness whenever the surface is
> illuminated (regardless of incident light angle):
>
> finish { ambient 0 diffuse 1 brilliance 0 }
>
> Finally, set up the light source to have no distance-based attenuation
> (i.e. use `fade_power 0`).
>
>
> This should give you an output image where the brightness of each pixel
> corresponds to the distance the light ray has travelled.
>
>
> Make sure to use a high bit depth for the output image, and either use
> linear encoding (`File_Gamma=1`) or be aware that your pixel values will
> not correspond linearly to distance travelled.
Thank you for the reply. This could be a very interesting approach.
Maybe a trivial question but...about the values x,y,z in the definition of the
function Fn:
Fn = function(x,y,z) {
FnDist(x-xC,y-yC,z-zC) +
FnDist(x-xL,y-yL,z-zL)
what do they represent for POV-ray?
I was thinking I could introduce a such function directly as a light attenuation
function in the definition of light source.
What do you think about?
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