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AssigneeNone recorded
InventorsRaymond Macdonald Russell, Stuart Alexander Watson
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A method of producing a control data set capable of controlling a machine tool comprising the steps of: (i) providing processing means capable of generating data and causing said processing means to generate a parametric surface indicative of the shape of an object; (ii) causing said processing means to generate a mesh indicative of a shape of a relief, said relief comprising height contours and said mesh having at least one edge; (iii) causing said processing means to perform one of the following: project said mesh onto said surface; wrap said mesh on to said surface; intersect said mesh with said surface, so as to preserve said height contours of said relief relative to one another; and (iv) causing said processing means to determine a trim boundary of the surface, said trim boundary having at least one edge, by performing one of the following: projecting said mesh into said surface; wrapping said mesh onto said surface; or intersecting said mesh with said surface, using said processing means such that said at least one edge of said mesh and said at least one edge of said trim boundary are contiguous.
A method of generating a computer model which provides means for processing data, capable of generating, of processing, of transforming and of storing said data and further comprising the steps of:
A system for generating a computer model, said system comprising a parametric surface generator capable of generating a surface and arranged to generate a parametric surface, a mesh generator capable of generating a mesh and arranged to generate a mesh representing a relief, a boundary generating means capable of generating a boundary and arranged to generate a boundary at least a portion of which is arranged to lie within said parametric surface generated by said parametric surface generator, and a projector means, for projecting said mesh and arranged to project said mesh onto said boundary.
A method of generating a computer model which provides means for processing data, capable of generating, of processing, of transforming and of storing said data and further comprising the steps of:
A computer readable memory device arranged to be encoded with a data structure for producing a computer model comprising a first entry and a second entry, said first entry comprising a parameter relating to a trim boundary of a parametric surface, said second entry comprising a parameter relating to an outer edge of a polygonal mesh;
Dependencies are inferred from the claim text.
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Three-dimensional [3D] modelling for computer graphics: finite element generation, e.g. wire-frame surface description, tesselation
Image data processing or generation, in general
Term end not estimated
This invention relates to a method and system for the generation of a computer model. More particularly but not exclusively it relates to a method and system for the generation of a Computer Aided Design (CAD) model.
The computer modelling of ‘real world’ objects (often used for the generation of control commands for machine tools) typically employs one of two techniques—either surface or solid modelling.
Surface modelling represents an object by modelling its outer ‘skin’, and allows pieces of this skin to the modelled separately—with no restriction on the pieces forming a closed, ‘watertight’ boundary.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a representation of a screen dump of a prior art solid modelling package;
FIG. 2 is a representation of a prior art arrangement of a parametric surface and a polygonal mesh superposed upon the surface, showing that the surface is untrimmed and is penetrated by the mesh;
Solid modelling is well known but for the avoidance of doubt a brief description follows. Objects are built up from building blocks, for example a cuboid or a cylinder. A closed skin is defined over the object. This skin is generally referred to as a ‘Boundary Representation’, the resultant solid being a Boundary Representation, or Brep solid. The surfaces that constitute the Brep are typically stored as parametric surfaces, each surface of the solid is called a face. Some modelling software packages represent the Brep as a mesh of planar facets. The facets are typically planar polygons with triangular facets being most commonly used because of their simplicity. Further building blocks are added to, or subtracted from, the model to yield projections and recesses of the object being modelled, respectively.
Each addition of a building block to, or subtraction of a building block from, the model is termed ‘a feature’ of the model. A history of the sequence of features associated with the model is typically recorded in the form of a feature tree. If the operations are simple Boolean operations of basic primitive shapes the solid is typically referred to as having a Constructive Solid Geometry (CSG). Most solid modelling software packages combine Brep and feature history by storing both the final Brep and a history of all commands used in building the solid. Thus, a user is able to replay the features of the model and alter an earlier feature. The effect of changing an early feature cascades down through the intervening features and is displayed in the current model. This arrangement is easy to use as changes to the model can be made at any feature and the effect of the change upon the final model readily viewed.
Additionally, features are not always easily distinguishable from the model and the modelling package will typically display the feature tree as a user-interface that allows features to be selected and operated on. Each feature in the feature tree will usually have a dialogue box associated with it that allows the feature to be edited.