Greetings fellow ray-tracers,

I've been ray-tracing off and on for the last two years when I can find
time from daily work schedule.
I'm designing a glass bowl of sorts and I'm having trouble with the CSG
merge

I've started with an inner and outer sphere where I have taken the
difference between the outer and inner sphere to create a 'hollow'
globe_1.

I then take this globe object stretch it a bit by the y-axis and declare
it as globe_2.

I then position globe_2 above globe_1 and wrap the merge command hoping
it eliminate the intersecting surfaces between the two, but after
making  z-plane intersection test to see if these intersecting surfaces
remain..alas they are still there.

Many thanks in advance if you can help me with this problem or point out
where my logic fails in the attached pov file

Ronald F. Hicks
dag### [at] yahoocom

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Attachments:
Download 'test_merge.pov.txt' (2 KB)

It's could be a case of inside/outside where the inner sphere used to
difference away the hollow is still inversed as far as what the merge
statement is seeing.
Anyway, you might want to at least try the 'inverse' keyword in there
someplace, either in the whole merge or in one of the globe shapes.

Bob

"Ron Hicks" <dag### [at] yahoocom> wrote in message
news:3939EA7B.48F6AB00@yahoo.com...
| I'm designing a glass bowl of sorts and I'm having trouble with the CSG
| merge
|
| I've started with an inner and outer sphere where I have taken the
| difference between the outer and inner sphere to create a 'hollow'
| globe_1.
|
| I then take this globe object stretch it a bit by the y-axis and declare
| it as globe_2.
|
| I then position globe_2 above globe_1 and wrap the merge command hoping
| it eliminate the intersecting surfaces between the two, but after
| making  z-plane intersection test to see if these intersecting surfaces
| remain..alas they are still there.

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Maybe this will help illustrate better.  I don't think it actually is in need
of 'inverse' anywhere upon checking it out more.

light_source { <10,10,-10> color rgb 1}
camera {
  location  <0,0,-5>
  angle 40
  look_at   <0,0,0>
}
background {rgb<1,1,1>}

difference { // plane slicing
difference { // merge used here leaves both globes
difference { // globe_1
sphere {0,1} sphere {0,.9}
}
difference { // globe_2
sphere {0,1} sphere {0,.9}
 scale <1,1.25,1> translate .5*y
}
}
 plane {z,0}
 pigment {rgbf<1,0,0,.5>}
 finish {specular .5}
}

This will do what you wanted I think.  I'm not sure what you were seeing
yourself.  'merge' will leave both globes behind though so maybe that was why
you thought it was solid.  Maybe...

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Bob,

The file was very helpful with solving the cross section test I was
trying to perform.
I'm attaching the new file so you can see what I'm trying to get at.
Once you render this file you can see what I'm trying to make.
Now if I can get rid of the interior surfaces and have spotlight
illuminate the interior.
The piece will be intitled "Anatomy of Bong" show the entire bong and
then a cross-section of it by its side.
Of course I'm going to add a base and finish it off with a nice glass
texture.

 

Bob Hughes wrote:
> 
> Maybe this will help illustrate better.  I don't think it actually is in need
> of 'inverse' anywhere upon checking it out more.
> 
> light_source { <10,10,-10> color rgb 1}
> camera {
>   location  <0,0,-5>
>   angle 40
>   look_at   <0,0,0>
> }
> background {rgb<1,1,1>}
> 
> difference { // plane slicing
> difference { // merge used here leaves both globes
> difference { // globe_1
> sphere {0,1} sphere {0,.9}
> }
> difference { // globe_2
> sphere {0,1} sphere {0,.9}
>  scale <1,1.25,1> translate .5*y
> }
> }
>  plane {z,0}
>  pigment {rgbf<1,0,0,.5>}
>  finish {specular .5}
> }
> 
> This will do what you wanted I think.  I'm not sure what you were seeing
> yourself.  'merge' will leave both globes behind though so maybe that was why
> you thought it was solid.  Maybe...

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Attachments:
Download 'new_bong.pov.txt' (3 KB)

I've never had much fun trying to CSG hollow things.  It can be a lot of
trouble and this was no exception.  I like to struggle with it all though just
in case I might learn something new.  Well, I didn't really.  All I was able
to do is sloppily CSG those spheres together.  At least it's about right now.
If there is another way I don't think I know of it.

P.S. Don't think I want to know the reason for this particular scene.  I gave
up such "recreation" for better things long ago.

Bob

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Attachments:
Download 'new_old_bong.pov.txt' (4 KB)