# NurbsSurfaceResult¶

class NurbsSurfaceResult

Bases: ReferenceCount

The result of a NurbsSurfaceEvaluator. This object represents a surface in a particular coordinate space. It can return the point and/or normal to the surface at any point.

Inheritance diagram

NurbsSurfaceResult(NurbsSurfaceResult const&) = default

The constructor automatically builds up the result as the product of the indicated set of basis matrices and the indicated table of control vertex positions.

PN_stdfloat eval_extended_point(PN_stdfloat u, PN_stdfloat v, int d)

Evaluates the surface in n-dimensional space according to the extended vertices associated with the surface in the indicated dimension.

bool eval_extended_points(PN_stdfloat u, PN_stdfloat v, int d, PN_stdfloat result[], int num_values)

Simultaneously performs eval_extended_point() on a contiguous sequence of dimensions. The dimensions evaluated are d through (d + num_values - 1); the results are filled into the num_values elements in the indicated result array.

bool eval_normal(PN_stdfloat u, PN_stdfloat v, LVecBase3 &normal)

Computes the normal to the surface at the indicated point in parametric time. This normal vector will not necessarily be normalized, and could be zero. See also eval_point().

bool eval_point(PN_stdfloat u, PN_stdfloat v, LVecBase3 &point)

Computes the point on the surface corresponding to the indicated value in parametric time. Returns true if the u, v values are valid, false otherwise.

PN_stdfloat eval_segment_extended_point(int ui, int vi, PN_stdfloat u, PN_stdfloat v, int d) const

Evaluates the surface in n-dimensional space according to the extended vertices associated with the surface in the indicated dimension.

void eval_segment_extended_points(int ui, int vi, PN_stdfloat u, PN_stdfloat v, int d, PN_stdfloat result[], int num_values) const

Simultaneously performs eval_extended_point() on a contiguous sequence of dimensions. The dimensions evaluated are d through (d + num_values - 1); the results are filled into the num_values elements in the indicated result array.

void eval_segment_normal(int ui, int vi, PN_stdfloat u, PN_stdfloat v, LVecBase3 &normal) const

As eval_segment_point(), but computes the normal to the surface at the indicated point. The normal vector will not necessarily be normalized, and could be zero.

void eval_segment_point(int ui, int vi, PN_stdfloat u, PN_stdfloat v, LVecBase3 &point) const

Evaluates the point on the surface corresponding to the indicated value in parametric time within the indicated surface segment. u and v should be in the range [0, 1].

The surface is internally represented as a number of connected (or possibly unconnected) piecewise continuous segments. The exact number of segments for a particular surface depends on the knot vector, and is returned by get_num_segments(). Normally, eval_point() is used to evaluate a point along the continuous surface, but when you care more about local continuity, you can use eval_segment_point() to evaluate the points along each segment.

PN_stdfloat get_end_u(void) const

Returns the last legal value of u on the surface.

PN_stdfloat get_end_v(void) const

Returns the last legal value of v on the surface.

int get_num_u_segments(void) const

Returns the number of piecewise continuous segments within the surface in the U direction. This number is usually not important unless you plan to call eval_segment_point().

int get_num_v_segments(void) const

Returns the number of piecewise continuous segments within the surface in the V direction. This number is usually not important unless you plan to call eval_segment_point().

PN_stdfloat get_segment_u(int ui, PN_stdfloat u) const

Accepts a u value in the range [0, 1], and assumed to be relative to the indicated segment (as in eval_segment_point()), and returns the corresponding u value in the entire surface (as in eval_point()).

PN_stdfloat get_segment_v(int vi, PN_stdfloat v) const

Accepts a v value in the range [0, 1], and assumed to be relative to the indicated segment (as in eval_segment_point()), and returns the corresponding v value in the entire surface (as in eval_point()).

PN_stdfloat get_start_u(void) const

Returns the first legal value of u on the surface. Usually this is 0.0.

PN_stdfloat get_start_v(void) const

Returns the first legal value of v on the surface. Usually this is 0.0.