On Sat, 15 Apr 2000 12:09:08 -0500, Chris Huff wrote:
>
>Sorry, but I don't think this is possible...at least, not with the type 
>of blob POV uses(are there other kinds that would make this possible?).
>A blob object is just an isosurface, all points where the sum of the 
>field of all of the components is equal to a certain threshold value. I 
>don't think it is possible to exclude components based on the "branch" 
>they are in.

How about adding a threshold identifier so that you could specify which 
object another will blob with, and if you specify two in the same object
it will blob with the other two within the block that have the same 
identifiers eg:

blob {
      ThresholdIdentInit{FRED,JIM} //Initialises the Threshold Identifiers

      sphere{<0,0,0>, 0.7, 0.8 
             ThresholdIdent{FRED}
            }

      sphere{<0,0.5,0>,0.7 ,0.8
             ThresholdIdent {FRED,JIM} 
            }

      sphere{<0.5,0.5,0>,0.7 ,0.7
             ThresholdIdent {JIM}
            }

      sphere{<0.5,0.5,0.5>,0.7 0.6
             ThresholdIdent {JIM,FRED} // the order shouldn't make a difference.
            }

     }  // End of blob. 


If a component doesn't have a ThresholdIdent it acts as normal and if a blob
doesn't have a ThresholdIdentInit at the beginning then the blob acts as 
normal.

My logical thinking says that this should be possible but I've never looked
at the pov code and I'm not much of a programmer so the rest is up to the
experts.

-- 
Cheers
Steve              email mailto:sjl### [at] ndirectcouk

%HAV-A-NICEDAY Error not enough coffee  0 pps. 

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In article <slr### [at] zero-ppslocaldomain>, 
sjl### [at] ndirectcouk wrote:

> How about adding a threshold identifier so that you could specify which 
> object another will blob with, and if you specify two in the same object
> it will blob with the other two within the block that have the same 
> identifiers eg:
> 
> blob {...}
> 
> If a component doesn't have a ThresholdIdent it acts as normal and if 
> a blob doesn't have a ThresholdIdentInit at the beginning then the 
> blob acts as normal.
> 
> My logical thinking says that this should be possible but I've never 
> looked at the pov code and I'm not much of a programmer so the rest 
> is up to the experts.

I don't think this would be any different from having multiple blob 
objects with some identical components. And I don't understand your 
reasoning in calling it a "threshold identifier", since it doesn't seem 
to have anything to do with the threshold...a possible sign that I 
completely misunderstood what you were trying to say. :-(

And anyway, you still have the problem of determining which set of blob 
components to use. The components are not blobbed together one by one 
and the results rendered, their contributions to a point are added 
together and the equation solved for each ray. How do you decide which 
components to use in the solving process when you have a ray, or even a 
point, as the starting information?

The only way I can see something like this being possible is by making a 
new type of blobby object which takes components that are turned into a 
mesh, and blobbed together one by one in a tree structure. Then the mesh 
object would be rendered...of course, this has all the problems of 
tesselating into triangles(probably even harder because of the specific 
order the components would be combined in).

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

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