POV-Ray : Newsgroups : povray.bugreports : difference normal bug? Server Time
31 Oct 2024 23:29:30 EDT (-0400)
  difference normal bug? (Message 1 to 3 of 3)  
From: Lewis Sellers
Subject: difference normal bug?
Date: 3 Oct 1998 00:44:30
Message: <36159DB2.8630724B@usit.net>
Pardon me if my mathematics are insufficient to explain the problem
properly, but....

When doing some DIFFERENCEs where the, um, surfaces of the objects are
in the same plane it cuts a hole INTO the first object. not sure if it's
supposed to do this, or if it's a bug of somekind.


Follows code that shows the prob. It's a house block where I'm
subtracting a stair well. I got around this by the hack of adding .01 to
some of the coordinates. That works.

P200MMX w/ 128MB RAM running NT 4 SP3.
Using the new Povray 3.1 (non beta).




#declare T_Wall =
texture {
    pigment {
        color rgb<1,1,1>
    }
    finish {
        ambient 0.2
        brilliance .01
        diffuse 1
        roughness 1
        reflection 0
    }
}
#declare T_WallPaper =
texture {
    pigment {
        wood
        turbulence 0
        color_map {
            [0 color rgb<.8,.8,.75>]
            [.2 color rgb<1,1,1>]
        }
        scale .2
        rotate <-90,0,0>
    }
    finish {
        ambient 0.2
        brilliance .01
        diffuse 1
        roughness 1
        reflection 0
    }
}
#declare T_Masonry =
texture {
    pigment {
        brick color rgb<.6,.6,.6>, color rgb<1,1,.9>
        brick_size <8,3,4.5>
        mortar .25
        scale 1/8
        turbulence 0
    }
    finish {
        ambient 0.2
        brilliance .01
        diffuse 1
        roughness 1
        reflection 0
    }
}

camera {           
    angle 90 //wide-angle
    //location<36,3,-5>
    location<32,1,-5>
    look_at <32,0,12>
}

    light_source {
        <36,1,-4>
        color rgb<.9,.9,.8>
        fade_distance 2
        fade_power 1
    }
    light_source {
        <32,7.5,5>
        color rgb<.8,.8,1>
        fade_distance 2
        fade_power 1
    }
    light_source {
        <40,1,9>
        color rgb<1,.5,.5>
        fade_distance 2
        fade_power 1
    }

difference {
        merge {
            box { <0,  -.1, 0>, <51.5,8.5,29.5> texture {T_Wall} }
            box { <0,  -.1, 0>, <51.5,-4,29.5> texture {T_Masonry} }
            box { <-.5,-4,  -.5>, <52,-10.6,30> texture {T_Masonry} }
        }
        merge {
            box { <29.5,   3, 6.1>, <35.5,  -5, -1.5> }
            box { <29.5, -.1, 9.6>, <35.5, 8.1, 0.5> }
            texture {T_WallPaper}
        }
}





-- 
Lewis A. Sellers: writer and contract Multimedia Website Developer
mailto:lse### [at] usitnet (The Fourth Millennium Foundation)
http://www.public.usit.net/lsellers/ & http://www.fourthfoundation.com
http://brain-of-pooh.tech-soft.com/users/critters/bios/sellers_lewis.html

You can bug the living bejesus out of me live on ICQ @ 491461
(If I don't get back to you within a month, I'm out of prozac in some
dark corner somewhere screaming things quite unintelligable but -- most
curiously -- thick with a sumerian accent.)

"The comedy is over" -i pagliacci


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From: Nathan Kopp
Subject: Re: difference normal bug?
Date: 3 Oct 1998 20:28:50
Message: <3616B38A.6A2E6A18@ltu.edu>
> When doing some DIFFERENCEs where the, um, surfaces of the objects are
> in the same plane it cuts a hole INTO the first object. not sure if it's
> supposed to do this, or if it's a bug of somekind.

I couldn't see the problem from your code (I didn't really know what I was
looking for).  First, a difference is intended to cut a hole in the first
object, subtracting one object from another.  Secondly, whenever two surfaces
coincide, it will always cause a problem, since the render will have to decide
which intersection to use.  As a general rule, you should never have two
surfaces directly coincide (sometimes it's OK, but not usually).

-Nathan


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From: Lewis Sellers
Subject: Re: difference normal bug?
Date: 3 Oct 1998 22:52:19
Message: <3616D4E1.DB441587@usit.net>
Nathan Kopp wrote:
> 
> > When doing some DIFFERENCEs where the, um, surfaces of the objects are
> > in the same plane it cuts a hole INTO the first object. not sure if it's
> > supposed to do this, or if it's a bug of somekind.
> 
> I couldn't see the problem from your code (I didn't really know what I was
> looking for).  First, a difference is intended to cut a hole in the first
> object, subtracting one object from another.  Secondly, whenever two surfaces
> coincide, it will always cause a problem, since the render will have to decide
> which intersection to use.  As a general rule, you should never have two
> surfaces directly coincide (sometimes it's OK, but not usually).
> 
> -Nathan

Hmm. That's what someone else just told me. It does seem logical though
that the solid object (A) should stay a solid object and not be skinned.
:) Oh well.

I could have sworn it worked properly back in 3.0 a few days ago though.
Let me check.... Nope. How'd I miss that before? Bad lighting maybe. ;-)

Look in povray.general. I'll post a pic there. Not that it matters, I
guess, since we all seem to know what i'm talking about. Need a
povray.thisiswhatthebuglookslike newsgroup to post them in to clarify
things.

Thanks, :)
--min

-- 
Lewis A. Sellers: writer and contract Multimedia Website Developer
mailto:lse### [at] usitnet (The Fourth Millennium Foundation)
http://www.public.usit.net/lsellers/ & http://www.fourthfoundation.com
http://brain-of-pooh.tech-soft.com/users/critters/bios/sellers_lewis.html

You can bug the living bejesus out of me live on ICQ @ 491461
(If I don't get back to you within a month, I'm out of prozac in some
dark corner somewhere screaming things quite unintelligable but -- most
curiously -- thick with a sumerian accent.)

"The comedy is over" -i pagliacci


Post a reply to this message

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