"Nekar Xenos" <nek### [at] gmailcom> wrote:

> Do you mean like the shadows in Sky Captain and Toy Story 1?
>
> Such shadows are totally unrealistic because they are blurred the same
> amount not matter how far away they are from the object. Just because
> other renderers do it, doesn't mean it is correct. These soft shadows are
> a scan-line renderer shortcut for actual area light shadows that render
> longer. Pov-Ray is not a scan-line renderer, it is a ray-tracer. I suggest
> you use an Area Light with jitter, circular and orient, and making it the
> size of the globe it represents to give you a more realistic soft shadow.
>
> Take a look at any soft shadow in real life and you will see that where
> the shadow meats the object casting it, the shadow is sharp. The further
> away the shadow is from the object, the softer the shadow is.

I think you're thinking of shadow maps. What I mean is a commonly used method of
faking 'true' soft shadows that do spread out the further away an object is from
the thing it casts its shadow onto, no matter what type of light source is used.

In this method the shadow rays would be traced from the hitpoint and spread out
more the father away the object casting the shadow is, causing a softer shadow
to form. For example, a shadow ray would hit a ground plane, then something like
16 shadow rays could then be traced from the hitpoint on the ground plane up to
a light source, each randomly offset from the path to the light source by say 10
degrees.
     That would give you a ~20 degree 'cone' of shadow rays going up from the
hitpoint to the light. Some shadow rays would hit an object, e.g. a sphere, and
some would miss, so then the average colour of all those rays would be a shade
of grey. The closer towards an object the more rays would hit the sphere,
leading to a darker colour and vice versa. And the farther away the object is
the more rays from farther hitpoints would hit it too, leading to a much more
'spread out' and softer shadow.

Post a reply to this message