# NurbsSurfaceEvaluator¶

class NurbsSurfaceEvaluator

Bases: ReferenceCount

This class is an abstraction for evaluating NURBS surfaces. It accepts an array of vertices, each of which may be in a different coordinate space (as defined by a NodePath), as well as an optional knot vector.

Inheritance diagram

NurbsSurfaceEvaluator(void)
NurbsSurfaceEvaluator(NurbsSurfaceEvaluator const&) = default
PointerTo<NurbsSurfaceResult> evaluate(NodePath const &rel_to = NodePath()) const

Returns a NurbsSurfaceResult object that represents the result of applying the knots to all of the current values of the vertices, transformed into the indicated coordinate space.

PN_stdfloat get_extended_vertex(int ui, int vi, int d) const

Returns an n-dimensional vertex value. See set_extended_vertex(). This returns the value set for the indicated dimension, or 0.0 if nothing has been set.

int get_num_u_knots(void) const

Returns the number of knot values in the surface in the U direction. This is based on the number of vertices and the order.

int get_num_u_segments(void) const

Returns the number of piecewise continuous segments in the surface in the U direction. This is based on the knot vector.

int get_num_u_vertices(void) const

Returns the number of control vertices in the U direction on the surface. This is the number passed to the last call to reset().

int get_num_v_knots(void) const

Returns the number of knot values in the surface in the V direction. This is based on the number of vertices and the order.

int get_num_v_segments(void) const

Returns the number of piecewise continuous segments in the surface in the V direction. This is based on the knot vector.

int get_num_v_vertices(void) const

Returns the number of control vertices in the V direction on the surface. This is the number passed to the last call to reset().

PN_stdfloat get_u_knot(int i) const

Returns the value of the nth knot.

int get_u_order(void) const

Returns the order of the surface in the U direction as set by a previous call to set_u_order().

PN_stdfloat get_v_knot(int i) const

Returns the value of the nth knot.

int get_v_order(void) const

Returns the order of the surface in the V direction as set by a previous call to set_v_order().

LVecBase4 const &get_vertex(int ui, int vi) const
LVecBase4 get_vertex(int ui, int vi, NodePath const &rel_to) const

Returns the nth control vertex of the surface, relative to its indicated coordinate space.

Returns the nth control vertex of the surface, relative to the given coordinate space.

NodePath get_vertex_space(int ui, int vi, NodePath const &rel_to) const

Returns the coordinate space of the nth control vertex of the surface, expressed as a NodePath.

void normalize_u_knots(void)

Normalizes the knot sequence so that the parametric range of the surface in the U direction is 0 .. 1.

void normalize_v_knots(void)

Normalizes the knot sequence so that the parametric range of the surface in the U direction is 0 .. 1.

void output(std::ostream &out) const
void reset(int num_u_vertices, int num_v_vertices)

Resets all the vertices and knots to their default values, and sets the surface up with the indicated number of vertices. You must then call set_vertex() repeatedly to fill in all of the vertex values appropriately.

void set_extended_vertex(int ui, int vi, int d, PN_stdfloat value)

Sets an n-dimensional vertex value. This allows definition of a NURBS surface or surface in a sparse n-dimensional space, typically used for associating additional properties (like color or joint membership) with each vertex of a surface.

The value d is an arbitrary integer value and specifies the dimension of question for this particular vertex. Any number of dimensions may be specified, and they need not be consecutive. If a value for a given dimension is not specified, is it implicitly 0.0.

The value is implicitly scaled by the homogenous weight value–that is, the fourth component of the value passed to set_vertex(). This means the ordinary vertex must be set first, before the extended vertices can be set.

void set_extended_vertices(int ui, int vi, int d, PN_stdfloat const values[], int num_values)

Simultaneously sets several extended values in the slots d through (d + num_values - 1) from the num_values elements of the indicated array. This is equivalent to calling set_extended_vertex() num_values times. See set_extended_vertex().

void set_u_knot(int i, PN_stdfloat knot)

Sets the value of the nth knot. Each knot value should be greater than or equal to the preceding value. If no knot values are set, a default knot vector is supplied.

void set_u_order(int u_order)

Sets the order of the surface in the U direction. This resets the knot vector to the default knot vector for the number of vertices.

The order must be 1, 2, 3, or 4, and the value is one more than the degree of the surface.

void set_v_knot(int i, PN_stdfloat knot)

Sets the value of the nth knot. Each knot value should be greater than or equal to the preceding value. If no knot values are set, a default knot vector is supplied.

void set_v_order(int v_order)

Sets the order of the surface in the V direction. This resets the knot vector to the default knot vector for the number of vertices.

The order must be 1, 2, 3, or 4, and the value is one more than the degree of the surface.

void set_vertex(int ui, int vi, LVecBase4 const &vertex)
void set_vertex(int ui, int vi, LVecBase3 const &vertex, PN_stdfloat weight = 1.0)

Sets the nth control vertex of the surface, as a vertex in 4-d homogeneous space. In this form, the first three components of the vertex should already have been scaled by the fourth component, which is the homogeneous weight.

Sets the nth control vertex of the surface. This flavor sets the vertex as a 3-d coordinate and a weight; the 3-d coordinate values are implicitly scaled up by the weight factor.

void set_vertex_space(int ui, int vi, NodePath const &space)
void set_vertex_space(int ui, int vi, std::string const &space)

Sets the coordinate space of the nth control vertex. If this is not specified, or is set to an empty NodePath, the nth control vertex is deemed to be in the coordinate space passed to evaluate().

This specifies the space as a fixed NodePath, which is always the same NodePath. Also see setting the space as a path string, which can specify a different NodePath for different instances of the surface.

Sets the coordinate space of the nth control vertex. If this is not specified, or is set to an empty string, the nth control vertex is deemed to be in the coordinate space passed to evaluate().

This specifies the space as a string, which describes the path to find the node relative to the rel_to NodePath when the surface is evaluated.