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The mesh object can be used to efficiently store large numbers of triangles. Its syntax is:
MESH:
mesh
{
MESH_TRIANGLE...
[MESH_MODIFIER...]
}
MESH_TRIANGLE:
triangle
{
<Corner_1>, <Corner_2>, <Corner_3>
[uv_vectors <uv_Corner_1>, <uv_Corner_2>, <uv_Corner_3>]
[MESH_TEXTURE]
} |
smooth_triangle
{
<Corner_1>, <Normal_1>,
<Corner_2>, <Normal_2>,
<Corner_3>, <Normal_3>
[uv_vectors <uv_Corner_1>, <uv_Corner_2>, <uv_Corner_3>]
[MESH_TEXTURE]
}
MESH_TEXTURE:
texture { TEXTURE_IDENTIFIER }
texture_list {
TEXTURE_IDENTIFIER TEXTURE_IDENTIFIER TEXTURE_IDENTIFIER
}
MESH_MODIFIER:
inside_vector <direction> | hierarchy [ Boolean ] |
OBJECT_MODIFIER
Mesh default values:
hierarchy : on
Any number of triangle and/or smooth_triangle statements can be used and each of those
triangles can be individually textured by assigning a texture identifier to it. The texture has to be declared before
the mesh is parsed. It is not possible to use texture definitions inside the triangle or smooth triangle statements.
This is a restriction that is necessary for an efficient storage of the assigned textures. See "Triangle
and Smooth Triangle" for more information on triangles.
The mesh object can support uv_mapping. For this, per triangle the keyword uv_vectors
has to be given, together with three 2D uv-vectors. Each vector specifies a location in the xy-plane from which the
texture has to be mapped to the matching points of the triangle. Also see the section uv_mapping.
The mesh's components are internally bounded by a bounding box hierarchy to speed up
intersection testing. The bounding hierarchy can be turned off with the hierarchy off keyword. This
should only be done if memory is short or the mesh consists of only a few triangles. The default is hierarchy on.
Copies of a mesh object refer to the same triangle data and thus consume very little memory. You can easily trace a
hundred copies of a 10000 triangle mesh without running out of memory (assuming the first mesh fits into memory). The
mesh object has two advantages over a union of triangles: it needs less memory and it is transformed faster. The
memory requirements are reduced by efficiently storing the triangles vertices and normals. The parsing time for
transformed meshes is reduced because only the mesh object has to be transformed and not every single triangle as it
is necessary for unions.
The mesh object can currently only include triangle and smooth triangle components. That restriction may change,
allowing polygonal components, at some point in the future.
Triangle mesh objects (mesh and mesh2) can now be used in CSG objects such as difference
and intersect, because, after adding inside_vector, they do have a defined 'inside'. This will only work
for well-behaved meshes, which are completely closed volumes. If meshes have any holes in them, this might work, but
the results are not guaranteed.
To determine if a point is inside a triangle mesh, POV-Ray shoots a ray from the point in some arbitrary direction.
If this vector intersects an odd number of triangles, the point is inside the mesh. If it intersects an even number of
triangles, the point is outside of the mesh. You can specify the direction of this vector. For example, to use +z
as the direction, you would add the following line to the triangle mesh description (following all other mesh data,
but before the object modifiers).
inside_vector <0, 0, 1>
This change does not have any effect on unions of triangles... these will still be always hollow.
More about "uv_mapping"
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