Le 12/10/2017 à 18:41, Alain a écrit :
> Le 17-10-12 à 02:36, And a écrit :
> 
>>
>> Well, that it seems poseray adds a symbolic vector, because <0,0,1> 
>> does not
>> inside my model in fact. And it shouldn't get such an information 
>> because the
>> mesh was output from sketchup it does not contain that, moreover most 
>> of the
>> mesh 3d model does not have a well construct that contain a inside/ 
>> outside
>> distinction.
>>
> 
> It's not a sympolic vector, it's a DIRECTION vector.
> To see if ANY point is inside the mesh, POV-Ray shoot a ray from that 
> point in the direction of the inside_vector.
> With the default vector rovided, the test ray is parallel to the Z axis 
> toward +Z.
> It's similar to the normal vector of a plane.

And to finish the explanation: POV-Ray counts the number of 
intersections from that point along that vector, to infinity.

When odd, the point is inside,
when even, the point is outside.

(Unless inside & outside were inverted)

Hence it's better for the vector to never be perpendicular to any normal 
of the triangles of the mesh, should bad luck occurs for a point in the 
exact plane of that triangle, the inside/outside test might be "fluffy".

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