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"Walls" are missing when using solid meshes in CSG. The problem is described in
more detail in this thread:
http://news.povray.org/povray.general/thread/%3Cweb.49407a1e34307b75ef318dca0%40news.povray.org%3E/?mtop=22
Here's a simple example scene:
camera
{
location -z * 6
look_at 0
right x*image_width/image_height
rotate x * 30
rotate y * -30
}
light_source
{
<-3, 9, -3>
color rgb 1
parallel
}
plane
{
y, 0
pigment {color rgbt <0,0,1,1/4,>}
}
difference
{
box
{
-1, 1
scale 1/2
}
mesh
{
triangle {<0,1,0,>, <1,1,0,>, <0,1,1,>}
inside_vector y
rotate y * 180
}
pigment {color rgbt <1,1,1,0,>}
}
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"SharkD" <nomail@nomail> wrote:
> "Walls" are missing when using solid meshes in CSG. The problem is described in
> more detail in this thread:
>
>
http://news.povray.org/povray.general/thread/%3Cweb.49407a1e34307b75ef318dca0%40news.povray.org%3E/?mtop=22
>
> Here's a simple example scene:
The problem with that scene is that the "solid mesh" isn't solid at all.
An "inside_normal" statement is not intended to make a mesh solid - it's just
intended to help reduce artifacts with solid (or at least "almost-solid")
meshes.
A solid mesh is instead any mesh whose surface - as defined by its triangles -
fully encloses some volume (the "inside"). The mesh in your sample scene,
having only a single triangle, obviously does not meet this requirement.
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"SharkD" <nomail@nomail> wrote:
> "Walls" are missing when using solid meshes in CSG. The problem is described in
> more detail in this thread:
>
>
http://news.povray.org/povray.general/thread/%3Cweb.49407a1e34307b75ef318dca0%40news.povray.org%3E/?mtop=22
I see now from clipka's explanation how the current behavior could be considered
useful. Without it, in poorly-formed meshes you would see prisms extending
tofrom the gaps to infinity along the vector defined by the inside_vector
statement. However, in some instances this behavior is not desirable.
Therefore, I propose that a flag be added to toggle this behavior on/off. Maybe
"open" or "hollow" could be used, but these terms don't correspond perfectly to
what is actually happening.
-Mike
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