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From: Tor Olav Kristensen
Subject: Concave shapes (43KB)
Date: 5 Oct 2000 15:11:45
Message: <39DC993C.5D889A93@online.no>
Yesterday I did some more work on some CSG-macros of mine.
They will "round off" any concave shape made with intersections
of planes, like the upper left shape.

The lower right shape shows how the resulting shape looks
like if both the edges and corners are wounded off.

The rendering is slow, so now I'm working on the macro
so that it will render much faster.

The upper right shape shows how the rounding looks like if
only the edges are rounded off.

And the lower left shape has different colours where "material"
has been "removed".

When I'm finished with the macros I'll post the source code
if anyone is interested.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: John VanSickle
Subject: Re: Concave shapes (43KB)
Date: 5 Oct 2000 15:21:46
Message: <39DC9C88.54B9888F@erols.com>
Tor Olav Kristensen wrote:
> 
> Yesterday I did some more work on some CSG-macros of mine.
> They will "round off" any concave shape made with intersections
> of planes, like the upper left shape.

Nota bene:  The shapes depicted are convex, not concave.

> The lower right shape shows how the resulting shape looks
> like if both the edges and corners are wounded off.
> 
> The rendering is slow, so now I'm working on the macro
> so that it will render much faster.

It's possible that making each face into a prism will help.  This
might be difficult, however.

Regards,
John


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From: Bob Hughes
Subject: Re: Concave shapes (43KB)
Date: 5 Oct 2000 15:29:14
Message: <39dc9e4a$1@news.povray.org>
"John VanSickle" <van### [at] erolscom> wrote in message
news:39DC9C88.54B9888F@erols.com...
| Tor Olav Kristensen wrote:
| >
| > Yesterday I did some more work on some CSG-macros of mine.
| > They will "round off" any concave shape made with intersections
| > of planes, like the upper left shape.
|
| Nota bene:  The shapes depicted are convex, not concave.

Well, not if you put the camera inside  :-)
You're quite the wizard with this kind of thing Tor, manipulating CSG
objects.  I just wanted to say that.
Any chance this could merge with one of the rock making includes?  Then
again, if this is slow and the rock makers are already slow it might be too
much for the typical scene file.
If the amount of roundedness can be adjusted it certainly could do well for
worn edges of such shapes anyway.

Bob


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From: Christoph Hormann
Subject: Re: Concave shapes (43KB)
Date: 5 Oct 2000 15:37:46
Message: <39DCA04A.D00B7A72@schunter.etc.tu-bs.de>
Tor Olav Kristensen wrote:
> 
> Yesterday I did some more work on some CSG-macros of mine.
> They will "round off" any concave shape made with intersections
> of planes, like the upper left shape.
> 
> The lower right shape shows how the resulting shape looks
> like if both the edges and corners are wounded off.
> 

looks good, how did you do it ? just CSG with planes, cylinders and spheres?

> The rendering is slow, so now I'm working on the macro
> so that it will render much faster.
> 

I suppose parsing will also be quite slow when working with complicated shapes.  

> The upper right shape shows how the rounding looks like if
> only the edges are rounded off.
> 
> And the lower left shape has different colours where "material"
> has been "removed".
> 

> When I'm finished with the macros I'll post the source code
> if anyone is interested.
> 

Sure we are :-)
I estimate it's quite a lot of work doing it, so thanks in advance...

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/


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From: Greg M  Johnson
Subject: truncated cubes.
Date: 6 Oct 2000 12:18:15
Message: <39DDC1B9.8637A48C@my-dejanews.com>
I want the coordinates for a truncated cube, in terms of triangles.

Can anyone point me to a reference for this?

In other words, I have seen the list of triangles needed for a cube/
rectangular solid based on 2 corner points.  I want 2D projection of this
solid to be, instead of a square, a symmetric 8-sided figure.


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From: Tor Olav Kristensen
Subject: Re: Concave shapes (43KB)
Date: 8 Oct 2000 22:30:52
Message: <39E0F57C.F4D1F1E0@hotmail.com>
John VanSickle wrote:
> 
> Tor Olav Kristensen wrote:
> >
> > Yesterday I did some more work on some CSG-macros of mine.
> > They will "round off" any concave shape made with intersections
> > of planes, like the upper left shape.
> 
> Nota bene:  The shapes depicted are convex, not concave.

Ugghh...  -How did that happen ?!

I even looked up convex in the dictionary 
to make sure that this wasn't only a 
norwegian word before I wrote the post.


> > The lower right shape shows how the resulting shape looks
> > like if both the edges and corners are wounded off.
> >
> > The rendering is slow, so now I'm working on the macro
> > so that it will render much faster.
> 
> It's possible that making each face into a prism will help.
> This might be difficult, however.

Yes I think you're right. I like that idea.
Prisms would probably make it faster.

It would not be very difficult. The needed 
data are already available within my macros.
But it will be some work determining how
data should be passed between the different 
macros in an efficient way.

There's one problem with prisms though:
The "stones" could not be used in further
CSG operations. E.g. like I did in my image; 
"Two spheres" posted to this news group 26.
April:

http://news.povray.org/3906D341.F1CD358C%40online.no

The two metal spheres are put inside the 
"space" cut out by a convex shape "rounded off"
by some preliminary versions of these macros.


Tor Olav

-- 
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: Tor Olav Kristensen
Subject: Re: Concave shapes (43KB)
Date: 8 Oct 2000 22:38:17
Message: <39E0F73A.B0E029C8@hotmail.com>
Bob Hughes wrote:
> ...
> You're quite the wizard with this kind of thing Tor, manipulating CSG
> objects.  I just wanted to say that.

Thank you !  - I'm flattered :)


> Any chance this could merge with one of the rock making includes?  Then
> again, if this is slow and the rock makers are already slow it might be too
> much for the typical scene file.

I'll look into it. Where can I find these 
rock making includes ?


> If the amount of roundedness can be adjusted it certainly could do well for
> worn edges of such shapes anyway.

The roundness can be adjusted by setting 
a "rounding radius" for the corners and
the edges.


Tor Olav

-- 
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: Tor Olav Kristensen
Subject: Re: Concave shapes (43KB)
Date: 8 Oct 2000 22:56:10
Message: <39E0FB6B.A7DFECE0@hotmail.com>
Christoph Hormann wrote:
> 
> Tor Olav Kristensen wrote:
> >
> > Yesterday I did some more work on some CSG-macros of mine.
> > They will "round off" any concave shape made with intersections
> > of planes, like the upper left shape.
> >
> > The lower right shape shows how the resulting shape looks
> > like if both the edges and corners are wounded off.
> >
> 
> looks good, how did you do it ? just CSG with planes, cylinders and spheres?

The starting (convex) shape is just 
intersections of all the involved planes.

Then one macro takes info about these planes 
and calculates where every possible triple 
of non parallel planes meets at potential 
corners (points).

Then another macro removes all the corners 
that are "false" (I.e. those that have one 
or more planes "below" themselves.)

Then some other macros receives the data 
about the final "true" corners and 
constructs the shapes (CSG with cylinders 
and spheres) that are used to "subtract"
from the starting shape.


> > The rendering is slow, so now I'm working on the macro
> > so that it will render much faster.
> >
> 
> I suppose parsing will also be quite slow when working with complicated shapes.

Yes, but not unbearable slow (as the pre-
liminary macros was).


> > When I'm finished with the macros I'll post the source code
> > if anyone is interested.
> >
> 
> Sure we are :-)
> I estimate it's quite a lot of work doing it, so thanks in advance...

Yes, there's a lot of info to manage within 
the macro. But I've now manage to make them 
much faster. But there's still some work 
left to make them stop calculating the same 
things over and over.

Maybe I can force myself to post some code 
soon, even if I'm not satisfied with it yet.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: Tor Olav Kristensen
Subject: Re: truncated cubes.
Date: 8 Oct 2000 23:00:45
Message: <39E0FC7F.44BB1E09@hotmail.com>
"Greg M. Johnson" wrote:
> 
> I want the coordinates for a truncated cube, in terms of triangles.
> 
> Can anyone point me to a reference for this?
> 
> In other words, I have seen the list of triangles needed for a cube/
> rectangular solid based on 2 corner points.  I want 2D projection of this
> solid to be, instead of a square, a symmetric 8-sided figure.

I'm not sure if I understand what you mean.

Can you try to explain more or post an 
image of this shape (e.g. made by inter-
section of planes) ?

By truncated cube, do you mean that the 
original corners are "cut" off ?


Tor Olav
-- 
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: Bob H 
Subject: Re: Concave shapes (43KB)
Date: 9 Oct 2000 03:10:35
Message: <39e1372b@news.povray.org>
"Tor Olav Kristensen" <tor### [at] hotmailcom> wrote in message
news:39E0F73A.B0E029C8@hotmail.com...
|
| I'll look into it. Where can I find these
| rock making includes ?

I'm having no luck finding the rock includes or macros, sorry.  One thing is
John Van Sickles and it seems Chris Huff may have something too (not sure),
and at the POV Objects Collection...  Steve Pidgeon was another person that
did one I know.

Bob


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