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trace(a, b) should give false when there is no intersection, something like
#if ( trace(a,b) )
....
#else
....
#end
but apparently, trace return a vector, when if statement needs a numeric
expression.
How can I check if two objects have any overlap in an if statement?
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hi,
"Kima" <nomail@nomail> wrote:
> I need an if statement to check if two objects have any intersection. I assumed
> trace(a, b) should give false when there is no intersection, something like
>
> #if ( trace(a,b) )
> ....
> #else
> ....
> #end
>
> but apparently, trace return a vector, when if statement needs a numeric
> expression.
>
> How can I check if two objects have any overlap in an if statement?
I guess you'd need to write a macro which takes the two objects and returns a
bool, true if the bounding boxes overlap (or whichever method you use to
determine "intersection").
regards, jr.
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"Kima" <nomail@nomail> wrote:
> but apparently, trace return a vector, when if statement needs a numeric
> expression.
Well, since trace {} returns <0, 0, 0> as the surface normal if it misses the
object, then you can just add together the x, y, and z components of the vector
to give a scalar value. Use abs() so nothing cancels out.
#declare TraceBool = abs(Normal.x)+abs(Normal.y)+abs(Normal.z);
http://news.povray.org/povray.binaries.tutorials/thread/%3Cweb.51f61e827603294573fc9ebb0%40news.povray.org%3E/
Gonna be tricky with CSG to look at the right place and get an accurate result.
If they are curves / algebraic surfaces, then I might see about doing the math
to see if there are any intersection points.
Just curious  what if you did:
intersection {
ObjectA
ObjectB
}
and computed the volume of the bounding box?
At the very least, if you're "scanning" with trace{}, then it would give you a
much smaller, and accurate volume to focus on.
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From: Alain Martel
Subject: Re: How to check if two objects have any intersection?
Date: 31 Jan 2020 12:01:23
Message: <5e345d63$1@news.povray.org>



 
 


Le 20200130 à 17:35, Bald Eagle a écrit :
>
> "Kima" <nomail@nomail> wrote:
>
>> but apparently, trace return a vector, when if statement needs a numeric
>> expression.
>
> Well, since trace {} returns <0, 0, 0> as the surface normal if it misses the
> object, then you can just add together the x, y, and z components of the vector
> to give a scalar value. Use abs() so nothing cancels out.
>
> #declare TraceBool = abs(Normal.x)+abs(Normal.y)+abs(Normal.z);
>
>
http://news.povray.org/povray.binaries.tutorials/thread/%3Cweb.51f61e827603294573fc9ebb0%40news.povray.org%3E/
>
> Gonna be tricky with CSG to look at the right place and get an accurate result.
> If they are curves / algebraic surfaces, then I might see about doing the math
> to see if there are any intersection points.
>
> Just curious  what if you did:
> intersection {
> ObjectA
> ObjectB
> }
> and computed the volume of the bounding box?
>
> At the very least, if you're "scanning" with trace{}, then it would give you a
> much smaller, and accurate volume to focus on.
>
>
You can test for the length of the normal vector.
If the trace encounter a surface, the length is 1. If it miss, the
length is zero.
So, it become :
#declare TraceBool = vlength(Normal);
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