POV-Ray : Newsgroups : povray.general : True Antialiasing : Re: True Antialiasing Server Time
4 Aug 2024 06:18:28 EDT (-0400)
  Re: True Antialiasing  
From: Warp
Date: 27 Aug 2003 17:30:46
Message: <3f4d2306@news.povray.org>
gramirosimancas <nomail@nomail> wrote:
> I was also thinking about doing the integral over time to have _True Motion
> Blur_, but let's first have pyramid raytracing and then move to integrating
> over time, as I think this would be an easy mathematical step once we have
> pyramid raytracing foundations.

  You make it sound like pyramid tracing could be possible in the first
place.
  There are several problems in getting the exact average of the intersection
of a (4-sided) pyramid and the scene:

  - Take a surface with a pigment and project a square onto it. The projection
of the square can have virtually any shape at free (because the surface can
have any shape). How do you calculate the exact average of the pigment
inside this freely-shaped area? Note that there's no limit on how
complex a pigment can be (it can be a fractal, a user-defined function...).

  - Getting the average pigment is only one small step. After that we need
the average lighting of the surface over the freely-shaped area. Now we
have a real problem. How do you calculate this average lighting? (The only
way I can think of is by taking samples inside the shape, but this is
exactly what we wanted to avoid in the first place).

  - And it gets more complex: Another object might be casting a shadow
which partially covers our freely-shaped area. How much of the area does
it cover? How do you calculate that (besides taking random samples)?

  - All the above deal with the case of the square being projected
entirely on one single surface. What happens if there's an edge of
the surface there? You will need to calculate how much each separate
surface take in our freely-shaped area and calculate the average of
their visible area.

  - What about reflections and refractions? When a square is projected
onto a surface and then reflected or refracted, it can continue forward
with virtually any shape. The surface where it is reflected/refracted
from can be as convoluted and complex you like. This affects the shape
of the square in really complex ways when we want to reflect/refract it.
  For example, imagine the projected square hitting the edge of a
reflective box. Part of the square will hit one side of the box and
the rest will hit another side of the box. Their reflection will go
in completely separate directions. Thus the square has been split into
two. Now imagine that it hits a vertex of the box. Imagine that it hits
the vertex of a shape where 8 surfaces meet. Imagine that these surfaces
are not flat...
  I believe you get the picture here.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -


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