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Yowser !
In the following bit of code the scene renders as expected when the ortographic
camera type is commented out. When it is used however the pattern on the z axis
plane continues uninterrupted on the y axis plane as if the pattern were applied
to both. Why ?
#declare Num=255;
#declare Twist= 180;
#declare foo =
pigment{ spotted turbulence z*.25 frequency 1
pigment_map {
[.25 granite color_map{[0 rgb< 1, 0,0.0>][1 rgb<.35,.2,0>]}]
[.50 spiral1 2 color_map{[0 rgb<.45,.3,0.0>][1 rgb<.35,.2,0>]}]
[.75 granite color_map{[0 rgb< 1, 0,.75>][1 rgb<.35,.2,0>]}]
}
}
plane{ -z, 0
texture {
finish { ambient 1 }
pigment { spherical
pigment_map {
#declare i=0;
#while (i<Num)
[i/Num foo rotate z*Twist*i/Num ]
#declare i=i+1;
#end
}
}
}
}
camera{ location <0,0,-6.5> look_at 0
// orthographic
}
plane{y,-1.5 pigment{rgb 1}finish{ambient .35 diffuse .35}}
background{rgb .65}
light_source{<0,100,-1000>,1}
--
Ken Tyler
Older Links: http://home.pacbell.net/tylereng/links.htm
Updated Links: http://home.pacbell.net/tylereng/bkmrk999.htm
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Ken wrote:
>
> In the following bit of code the scene renders as expected when the
ortographic
> camera type is commented out. When it is used however the pattern on the z
axis
> plane continues uninterrupted on the y axis plane as if the pattern were
applied
> to both. Why ?
The orthographic camera traces rays parallel to the viewing direction, in
this case +z. Your floor plane also lies in this direction (and its surface
is infinitely thin), so none of the camera rays will actually intersect it.
What you are seeing is the shadow of the floor plane, cast on to your wall -
the high ambient value of your wall pattern makes it look like a reflection
of sorts.
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Chris Colefax wrote:
>
> Ken wrote:
> >
> > In the following bit of code the scene renders as expected when the
> ortographic
> > camera type is commented out. When it is used however the pattern on the z
> axis
> > plane continues uninterrupted on the y axis plane as if the pattern were
> applied
> > to both. Why ?
>
> The orthographic camera traces rays parallel to the viewing direction, in
> this case +z. Your floor plane also lies in this direction (and its surface
> is infinitely thin), so none of the camera rays will actually intersect it.
> What you are seeing is the shadow of the floor plane, cast on to your wall -
> the high ambient value of your wall pattern makes it look like a reflection
> of sorts.
That is what I suspected but there is still something not quite right in the
explanation. If it
were a reflection of sort the pattern where it intersects
the y axis plane should be a mirror of the z axis plane. Instead I am seeing
a contiguous pattern emerging that defies the explanation you are giving.
I am sure it has much to do with the parallel rays of the camera type but
I am expecting different results. The wall as you put it is the plane with
the pattern applied to it and the "floor" has a simple white pigment attached
to it with it's own finish statement. Oh well back to the perspective camera :)
--
Ken Tyler
Older Links Page: http://home.pacbell.net/tylereng/links.htm
Updated Links Page: http://home.pacbell.net/tylereng/bkmrk999.htm
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When you use the orthographic camera, all the camera rays are parallel.
This means that when the points below the y=-1.5 plane are rendered, the
camera is effectively below this plane as well.
When the pixel representing <0,0,0> is rendered, the effective camera
location is <0,0,-6.5>, when <20,-10,0> is rendered, the camera is at
<20,-10,-6.5> etc.
So you are looking _under_ the horizontal plane.
Cheers, PoD.
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PoD wrote:
>
> When you use the orthographic camera, all the camera rays are parallel.
> This means that when the points below the y=-1.5 plane are rendered, the
> camera is effectively below this plane as well.
> When the pixel representing <0,0,0> is rendered, the effective camera
> location is <0,0,-6.5>, when <20,-10,0> is rendered, the camera is at
> <20,-10,-6.5> etc.
> So you are looking _under_ the horizontal plane.
>
> Cheers, PoD.
A good explaination and one I will accept. Next question then is should Pov
be able to see through solid object like this regardless of camera type ?
It seems to defy the laws of the physical world as I know them to be.
--
Ken Tyler
Older Links Page: http://home.pacbell.net/tylereng/links.htm
Updated Links Page: http://home.pacbell.net/tylereng/bkmrk999.htm
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On Sun, 08 Aug 1999 11:46:34 -0700, Ken <tyl### [at] pacbell net> wrote:
>
>PoD wrote:
>>
>> When you use the orthographic camera, all the camera rays are parallel.
>> This means that when the points below the y=-1.5 plane are rendered, the
>> camera is effectively below this plane as well.
>> When the pixel representing <0,0,0> is rendered, the effective camera
>> location is <0,0,-6.5>, when <20,-10,0> is rendered, the camera is at
>> <20,-10,-6.5> etc.
>> So you are looking _under_ the horizontal plane.
>>
>> Cheers, PoD.
>
> A good explaination and one I will accept. Next question then is should Pov
>be able to see through solid object like this regardless of camera type ?
>It seems to defy the laws of the physical world as I know them to be.
If you think of the orthographic camera as an array of cameras, one for each pixel and
all
parallel to each other, the result may be clearer.
David
------------
dav### [at] cwcomnet
http://www.hamiltonite.mcmail.com
------------
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Ken <tyl### [at] pacbellnet> wrote:
> That is what I suspected but there is still something not quite right in
the explanation. If it
> were a reflection of sort the pattern where it intersects
> the y axis plane should be a mirror of the z axis plane. Instead I am
seeing
> a contiguous pattern emerging that defies the explanation you are giving.
> I am sure it has much to do with the parallel rays of the camera type but
> I am expecting different results. The wall as you put it is the plane with
> the pattern applied to it and the "floor" has a simple white pigment
attached
> to it with it's own finish statement. Oh well back to the perspective
camera :)
You are indeed seeing the continuation of the wall pattern below the floor
plane - I said it *looks* like a reflection, because of the slightly darker
shading. If you reduce the ambient value of your wall texture you'll see
the lower section is completely in the shadow of the floor plane. The
difference is that the perspective camera traces rays from a single point,
whereas the orthographic camera traces the rays from a rectangle. This
means the floor plane actually intersects the camera, allowing you to see
both above and below it at the same time. You can achieve the same effect
with the perspective camera by intersecting it with the floor plane, eg.
camera {location <0, -1.5, -6.5>}, because once again the rays won't
actually hit the plane, making it invisible.
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Ok :)
--
Ken Tyler
http://home.pacbell.net/tylereng/index.html
I know you are but what am I ? <Unknown child>
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