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On Fri, 11 Aug 2000 09:48:41 +0800, Pabs wrote:
>Ron Parker wrote:
>
>> removed.
>
>???????????? Why
>IMVHO I don't think they should be removed esp the superellipsoid type
>one.
Fixed is more likely, but they obviously can't stay like they are.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
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> Rune <run### [at] iname com> wrote:
> : I've noticed before that you take what other people say very very literally.
Warp wrote:
> I'm sorry. I'm too perfectionist.
I have the same problem sometimes, and I put it down to being liberal.
As a lifelong science fiction fan, I'm accustomed to having people write
things that are outrageous at first sight but literally meaningful in
the proper context; so if a sentence puzzles me, I try to think *how* it
might be meaningful ... rather than thinking the writer was simply
sloppy.
--
Anton Sherwood -- br0### [at] p0b0xcom -- http://ogre.nu/
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Chris Huff wrote:
> The object pattern will only work for objects that are solid, and it
> isn't very friendly with the isosurface solving method. It is a "block
> pattern", and has only one of two states...basically meaning it has an
> infinite max_gradient. The isosurface algorithm can't easily cope with
> this.
I'm coming into this late and ignorant (haven't even compiled megapov
yet), so ignore me if I say something too stupid ...
Rune asked for a "function" equivalent to a given cone. What about
having this mean a function of the angle between the point in question,
the tip of the cone and the axis of the cone, ranging from 0 (axis,
outside) to 1 (axis, inside), adjusted so that a point on the surface of
the cone has function value 1/2 ?
The base of the cone can be represented by a ramp function, and thus the
whole finite cone function is the min() of these two.
To illustrate, suppose a standard cone has its apex at the origin, its
base at y=-1, and a 45 degree slope ...
float cone (float x, float y, float z)
{
float r = sqrt(x*x+z*z);
return 0.5 - atan2(y+r,r)/pi;
}
float cone_base (float x, float y, float z)
{
if (y<-2) return 0;
if (y>0) return 1;
return 1+y/2;
}
float finite_cone (float x, float y, float z)
{
return min( cone(x,y,z), cone_base(x,y,z) );
}
--
Anton Sherwood -- br0### [at] p0b0xcom -- http://ogre.nu/
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In article <39964397.4C636C6C@pobox.com>, Anton Sherwood
<bro### [at] poboxcom> wrote:
> Rune asked for a "function" equivalent to a given cone. What about
> having this mean a function of the angle between the point in question,
> the tip of the cone and the axis of the cone, ranging from 0 (axis,
> outside) to 1 (axis, inside), adjusted so that a point on the surface of
> the cone has function value 1/2 ?
The equation for a cone is actually simpler, just the equation for a
cylinder with the radius variable along the axis of the cone, like:
function {((Ra - Rb)*y + Rb) - sqrt(sqr(x) + sqr(z))}
(threshold value of 0, Ra is upper radius, Rb is lower radius)
You just have to clip it to the right length(possibly using the &
operator with two plane functions, or by just using the container
object). No trig functions are necessary. It is probably a good idea to
keep it axis-aligned, this makes some displacements easier to do,
simplifies the function, and is faster.
But what I think Rune wants is a way to use objects in isosurfaces
*without having to write the functions*. This would be difficult, it
would require adding density functions to objects which don't have them,
and would probably use a syntax similar to the pigment functions. An
alternative would be to use the proximity pattern, though it really
isn't very useable for this purpose in it's current state. You might
also be able to use the blob pattern, there may be some modifications
which would make it more useful for this.
--
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/
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