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Types, constants and utilities related to semi-sharp creasing – whose implementation is independent of the subdivision scheme. More...
#include <crease.h>
Public Types | |
| enum | Rule { RULE_UNKNOWN = 0, RULE_SMOOTH = (1 << 0), RULE_DART = (1 << 1), RULE_CREASE = (1 << 2), RULE_CORNER = (1 << 3) } |
Public Member Functions | |
| Crease () | |
| Crease (Options const &options) | |
| ~Crease () | |
| bool | IsUniform () const |
| float | ComputeFractionalWeightAtVertex (float vertexSharpness, float childVertexSharpness, int incidentEdgeCount, float const *incidentEdgeSharpness, float const *childEdgesSharpness) const |
| Transitional weighting: When the rules applicable to a parent vertex and its child differ, one or more sharpness values has "decayed" to zero. Both rules are then applicable and blended by a weight between 0 and 1 that reflects the transition. Most often this will be a single sharpness value that decays from within the interval [0,1] to zero – and the weight to apply is exactly that sharpness value – but more than one may decay, and values > 1 may also decay to 0 in a single step while others within [0,1] may remain > 0. So to properly determine a transitional weight, sharpness values for both the parent and child must be inspected, combined and clamped accordingly. More... | |
| void | GetSharpEdgePairOfCrease (float const *incidentEdgeSharpness, int incidentEdgeCount, int sharpEdgePair[2]) const |
| float | SharpenBoundaryEdge (float edgeSharpness) const |
| float | SharpenBoundaryVertex (float edgeSharpness) const |
| float | SubdivideUniformSharpness (float vertexOrEdgeSharpness) const |
| float | SubdivideVertexSharpness (float vertexSharpness) const |
| float | SubdivideEdgeSharpnessAtVertex (float edgeSharpness, int incidentEdgeCountAtEndVertex, float const *edgeSharpnessAroundEndVertex) const |
| void | SubdivideEdgeSharpnessesAroundVertex (int incidentEdgeCountAtVertex, float const *incidentEdgeSharpnessAroundVertex, float *childEdgesSharpnessAroundVertex) const |
| Rule | DetermineVertexVertexRule (float vertexSharpness, int incidentEdgeCount, float const *incidentEdgeSharpness) const |
| Rule | DetermineVertexVertexRule (float vertexSharpness, int sharpEdgeCount) const |
Protected Member Functions | |
| float | decrementSharpness (float sharpness) const |
| static float const | SHARPNESS_SMOOTH |
| static float const | SHARPNESS_INFINITE |
| static bool | IsSmooth (float sharpness) |
| static bool | IsSharp (float sharpness) |
| static bool | IsInfinite (float sharpness) |
| static bool | IsSemiSharp (float sharpness) |
Types, constants and utilities related to semi-sharp creasing – whose implementation is independent of the subdivision scheme.
Crease is intended to be a light-weight, trivially constructed class that computes crease-related properties – typically sharpness values and associated interpolation weights. An instance of Crease is defined with a set of options that include current and future variations that will impact computations involving sharpness values.
The Crease methods do not use topological neighborhoods as input. The methods here rely more on the sharpness values and less on the topology, so we choose to work directly with the sharpness values. We also follow the trend of using primitive arrays in the interface to encourage local gathering for re-use.
Note on the need for and use of sharpness values: In general, mask queries rely on the sharpness values. The common case of a smooth vertex, when known, avoids the need to inspect them, but unless the rules are well understood, users will be expected to provided them – particularly when they expect the mask queries to do all of the work (just determining if a vertex is smooth will require inspection of incident edge sharpness). Mask queries will occasionally require the subdivided sharpness values around the child vertex. So users will be expected to either provide them up front when known, or to be gathered on demand. Any implementation of subdivision with creasing cannot avoid subdividing the sharpness values first, so keeping them available for re-use is a worthwhile consideration.
| enum Rule |
Enum for the types of subdivision rules applied based on sharpness values (note these correspond to Hbr's vertex "mask"). The values are assigned to bit positions as it is useful to use bitwise operations to inspect collections of vertices (i.e. all of the vertices incident a particular face).
| Enumerator | |
|---|---|
| RULE_UNKNOWN | |
| RULE_SMOOTH | |
| RULE_DART | |
| RULE_CREASE | |
| RULE_CORNER | |
| float ComputeFractionalWeightAtVertex | ( | float | vertexSharpness, |
| float | childVertexSharpness, | ||
| int | incidentEdgeCount, | ||
| float const * | incidentEdgeSharpness, | ||
| float const * | childEdgesSharpness | ||
| ) | const |
Transitional weighting: When the rules applicable to a parent vertex and its child differ, one or more sharpness values has "decayed" to zero. Both rules are then applicable and blended by a weight between 0 and 1 that reflects the transition. Most often this will be a single sharpness value that decays from within the interval [0,1] to zero – and the weight to apply is exactly that sharpness value – but more than one may decay, and values > 1 may also decay to 0 in a single step while others within [0,1] may remain > 0. So to properly determine a transitional weight, sharpness values for both the parent and child must be inspected, combined and clamped accordingly.
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inlineprotected |
| Rule DetermineVertexVertexRule | ( | float | vertexSharpness, |
| int | incidentEdgeCount, | ||
| float const * | incidentEdgeSharpness | ||
| ) | const |
Rule determination: Mask queries do not require the Rule to be known, it can be determined from the information provided, but it is generally more efficient when the Rule is known and provided. In particular, the Smooth case dominates and is known to be applicable based on the origin of the vertex without inspection of sharpness.
| Rule DetermineVertexVertexRule | ( | float | vertexSharpness, |
| int | sharpEdgeCount | ||
| ) | const |
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Optional sharp features: Since options treat certain topological features as infinitely sharp – boundaries or (in future) non-manifold features – sharpness values should be adjusted before use. The following methods will adjust (by return) specific values according to the options applied.
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| float SubdivideEdgeSharpnessAtVertex | ( | float | edgeSharpness, |
| int | incidentEdgeCountAtEndVertex, | ||
| float const * | edgeSharpnessAroundEndVertex | ||
| ) | const |
| void SubdivideEdgeSharpnessesAroundVertex | ( | int | incidentEdgeCountAtVertex, |
| float const * | incidentEdgeSharpnessAroundVertex, | ||
| float * | childEdgesSharpnessAroundVertex | ||
| ) | const |
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inline |
Sharpness subdivision: The computation of a Uniform subdivided sharpness value is as follows:
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1.8.6 
