Are there any differences between a
Group and a CSG union? When to use
which?
They seem to do the same thing with with
objects. I don't see the use of groups.
Do they just exist to arrange objects
more conveniently? In that case the
Union CSG seems quite useless. Am I
making a fuss out of nothing or is there
really a difference?
Besides all that I would like to know
what stands CSG for.

(this is going to be a bit OT)
As you can see I am quite new to Moray.
The nicest picture I made was one of a
hotairballoon, flying over a landscape.
I made a heightfield of the landscape
with Terragen, imported it to Moray and
added the balloon, light and a camera. I
rendered the picture, threw away the
landscape exept for the balloon and it's
shadow with PSP (the shadow should have
the right size and shape because of the
special shape of the mountain. Then I
pasted the shadow and the balloon in the
landscape which I rendered with Terragen
itself using same Cameraposition,
lookatpoint and lightdirection.
Terragen makes very realistic
landscapes, Moray couldn't do that. Now
the problem is that the balloon doesn't
look realistic enough for the landscape.
Oh well. I can't have it all, can I?
I'll post the picture to the
povray.images newsgroup soon with
warnings it was made by a beginner.

Johan Walters

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A Group is a Moray feature that as such does not exist in POV-Ray, while CSG
("Constructive Solid Geometry", I think) Unions, Merges, Intersections and
Differences are POV-Ray features.
And yes, the Group in Moray is more or less a convenient thing to group
items, which you could do just the same with a CSG union.
Actually, Groups become Unions when exported to POV-Ray (afaik).

Johannes.

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Hi Walters, you recently wrote in moray.win:

> Are there any differences between a
> Group and a CSG union? When to use
> which?
As far as POV-Ray is concerned: 
They used to be different back in the old days. One of the earlier
POV-Ray versions had a composite object that you could group objects
with. This was later integrated with the union. So, by now, they are
basically the same thing. 

As far as Moray is concerned: 
You can only add primitive objects to a CSG, since otherwise the
render may not be what you wanted. Also, you cannot add a light to a
CSG object, you'll need to make a group if you want to place a light
in a group.

> Besides all that I would like to know
> what stands CSG for.
Constructive Solid Geometry.

- Lutz
  email : lut### [at] stmuccom
  Web   : http://www.stmuc.com/moray

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I always use Unions as oppose to th Morays Groups, the advantage being that
if your Union contains any other CSG objects, such as differences for
example, then you can evaluate the whole tree by just evaluating the parent
CSG.

Rick

Johannes Hubert <jhu### [at] algonetse> wrote in message
news:373b24da.0@news.povray.org...
> A Group is a Moray feature that as such does not exist in POV-Ray, while
CSG
> ("Constructive Solid Geometry", I think) Unions, Merges, Intersections and
> Differences are POV-Ray features.
> And yes, the Group in Moray is more or less a convenient thing to group
> items, which you could do just the same with a CSG union.
> Actually, Groups become Unions when exported to POV-Ray (afaik).
>
> Johannes.
>
>
>

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> As far as Moray is concerned:
> You can only add primitive objects to a CSG, since otherwise the
> render may not be what you wanted. Also, you cannot add a light to a
> CSG object, you'll need to make a group if you want to place a light
> in a group

Are you sure Lutz? I have several scene's that only use the CGS type Union
(as oppose to a group) and have lights, and all manner of other things in
them...

works fine for me anyhow :)

Rick

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> Are you sure Lutz? I have several scene's that only use the CGS type Union
> (as oppose to a group) and have lights, and all manner of other things in
> them...
> 
> works fine for me anyhow :)
> 
> Rick

Yep.  In pov-script, it is perfectly legal and working to use a light
in an union.  Of course, you cannot use a light in a difference or 
intersection...

Fabien.

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Hi Rick, you recently wrote in moray.win:

> Are you sure Lutz? I have several scene's that only use the CGS type Union
> (as oppose to a group) and have lights, and all manner of other things in
> them...
Oops. I think I'm losing touch with my own program<g>. That's what
happens when you don't ever get to use it because you're
programming<g>.

Yes, light sources can be added to CSGs. With spotlights you'll get a
warning about non-uniform scaling because while Moray will
non-uniformly scale the light cone, POV-Ray will not.

- Lutz
  email : lut### [at] stmuccom
  Web   : http://www.stmuc.com/moray

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But, if you then put a lens flare on the light source, it will not follow
any transformations of the CSG or group containing the light.

-Nathan

Lutz Kretzschmar wrote:
> 
> Hi Rick, you recently wrote in moray.win:
> 
> > Are you sure Lutz? I have several scene's that only use the CGS type Union
> > (as oppose to a group) and have lights, and all manner of other things in
> > them...
> Oops. I think I'm losing touch with my own program<g>. That's what
> happens when you don't ever get to use it because you're
> programming<g>.
> 
> Yes, light sources can be added to CSGs. With spotlights you'll get a
> warning about non-uniform scaling because while Moray will
> non-uniformly scale the light cone, POV-Ray will not.
> 
> - Lutz
>   email : lut### [at] stmuccom
>   Web   : http://www.stmuc.com/moray

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Hi Nathan Kopp, you recently wrote in moray.win:

> But, if you then put a lens flare on the light source, it will not follow
> any transformations of the CSG or group containing the light.
Ooops, true! But that is a bug in the LensFlare plugin.... Guess I'll
need to update it.

- Lutz
  email : lut### [at] stmuccom
  Web   : http://www.stmuc.com/moray

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