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Action:
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Creates a rail law or a list of rail laws for use by sweeping.
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Filename:
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kern/kern_scm/law_scm.cxx
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APIs:
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api_make_rails
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Syntax:
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(law:make-rails path [twist [axis [faces
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[user-rails [version]]]]])
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Arg Types:
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path
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edge | wire
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twist
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law
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axis
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law | (law ...)
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faces
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face | (face ...)
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user-rails
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law | (law ...)
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version
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version_tag
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Returns:
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law | (law ...)
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Description:
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This produces a rail law or a list of rail laws that can be used by sweeping or
law:hedgehog.
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If the
path is a single edge or a wire with a single underlying edge, then a single rail law is produced. Otherwise, the extension creates multiple rail laws, one for each underlying edge in the
path.
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The only required argument is the
path. If no other arguments are supplied, then the following default rails are created:
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-
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If the
path is planar, the rail law is the planar normal.
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-
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If the
path is a helix, the rail law points towards the axis.
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-
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If all edges in the wire are planar, then an array of rail laws is created, whereby each law in the array corresponds to an edge in the wire. The rail laws correspond to the planar normal of edges.
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-
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If the
path isn't one of the above cases, the rail uses minimum rotation.
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Because the input arguments are chained together,
"NULL" arguments (double quotation marks required) must be supplied for early elements in the argument list in order to change later arguments. If the input
path is composed of multiple pieces, such as a wire with more than one underlying edge, then list arguments must supply the same number of elements as the number of
path elements. They may pad their list with
"NULL" arguments (double quotation marks required).
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For example, assume that an input
path has three underlying edges. Assume that a list of
axis laws are to be supplied, but no twist law. The list of
axis laws would have to contain three elements. The list of
axis laws could contain
"NULL", which would result in the default rail for those corresponding portions of the
path. The example call might look like:
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(law:make-rails my-path "NULL"
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(list "NULL" my-law "NULL"))
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The
twist argument works on the whole rail. After the other rail parameters have been input and calculated, the law provided by
twist operates on the whole set of rails. This takes in an angle of twist per distance along the
path. The
twist argument can be
"NULL".
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The
axis argument is used for
path segments that have an implied center axis. An example of this might be a helix, an expanding helix, or the coil of a telephone handset cable. The
axis argument is the derivative of the implied center axis, which tells the implied axis direction. When the
axis is supplied, the created rails point towards it. The
axis list can be padded with
"NULL" for sections of the
path that do not have an implied axis.
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The
face argument is used when a portion of the
path segments borders a non-analytic face. The coedge of the wire provided as
path must actually belong to the face entity supplied. The face must be non-analytic. The resulting rail is oriented to the face normal. The
face list can be padded with
"NULL" for sections of the
path that do not have such a face.
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The
user-rails argument permits any default rail for a given section of the
path to be overridden by the user-supplied law in the list. The
user-rails list can be padded with
"NULL" for sections of the
path that are to use the default.
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The
version argument permits the user to specify a versiontag leaving the min_rotation_law as the rail. This behavior is not recommended for performance and robustness.
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Example:
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; law:make-rails
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; is:helix
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(define path1 (wire-body:offset (wire-body
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(edge:linear (position 0 0 0) (position 0 0 20)))
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5 "x"))
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;; path1
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(define rail-1 (law:make-rails path1))
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;; rail-1
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; #[law
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; "NORM(CROSS(DOMAIN(VEC(-(5*COS(X)),
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; -(5*SIN(X)),1),0,20),VEC(0,0,1)))"]
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; IF YOU WANT TO SEE THE RAILS, use law:hedgehog
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