60 lines
1.9 KiB
Plaintext
60 lines
1.9 KiB
Plaintext
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The user enters requests. A request might be a line segment, or a plane,
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or to step and repeat a group of entities, or anything else. Each
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request has a groupid associated with it; a group will contain one or
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more requests. The request will generate entities, and possibly equations.
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Special requests would include an include, which gives us a concept of
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hierarchy. An include pulls in all the entities from another SolveSpace
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part, and fixes them up to a rotation and translation; so that introduces
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six free variables. This means that the part is rigidly constrained,
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but that it still must be placed, and that entities within the included
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part are available to constrain against.
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An entity is some geometric thing in the sketch. This might be a
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line segment, or a datum point, or something else. Some requests
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correspond to a single entity, in a straightforward way. Other requests
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generate multiple entities, in some relationship (that is constrained
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automatically, through the generated equations) to other parts of the
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sketch. Each entity has a groupid, which is inherited from the request
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that generated it.
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One important entity is a pwl. That's a piecewise linear segment. Its
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endpoints are fixed, so it generates no parameters.
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The entity is described in terms of paramgroups. A paramgroup corresponds
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to one or more solver parameters, grouped in such a way as to have
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geometric meaning. For example, a point would correspond to three params,
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x, y, and z.
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The paramgroups break down in to params. These are the unknowns in the
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solver equations.
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The user enters constraints. Each constraint has groupid. The constraints
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generate equations too.
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The items that generate unknowns are:
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POINT:
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three unknowns, (x, y, z)
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Entities are:
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DATUM POINT:
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one point
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DATUM PLANE:
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one point; the plane is through that point, and normal to the
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vector from that point to the origin
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LINE SEGMENT:
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two endpoints
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