pe_elliptical_arc3(3g) — Subroutines

Name

pe_elliptical_arc3 − Specifies the 3D form of the elliptical arc primitive.

Operating States: PHOP, ∗, STOP, ∗
Digital PHIGS extension function
Creates a structure element

Syntax

void pe_elliptical_arc3 (
const Ppoint3   ∗center,        /∗ (I) Center of the elliptical arc, in
                                         modeling coordinates ∗/
const Pvec3     ∗major_axis,    /∗ (I) Vector that defines the x-axis ∗/
const Pvec3     ∗minor_axis,    /∗ (I) Vector that defines the y-axis ∗/
Pfloat           start_angle,   /∗ (I) Starting angle for drawing the
                                         arc, in radians ∗/
Pfloat           end_angle      /∗ (I) Ending angle for drawing the arc,
                                         in radians ∗/
)

Data Structures

typedef struct {
    Pfloat     x;    /∗ x coordinate ∗/
    Pfloat     y;    /∗ y coordinate ∗/
    Pfloat     z;    /∗ z coordinate ∗/
} Ppoint3;
typedef struct {
    Pfloat     delta_x;    /∗ delta x value ∗/
    Pfloat     delta_y;    /∗ delta y value ∗/
    Pfloat     delta_z;    /∗ delta z value ∗/
} Pvec3;

Description

pe_elliptical_arc3 specifies the three-dimensional form of the elliptical arc primitive. The elliptical arc 3 local coordinate system is the plane defined by the cross-product of the major and minor axes and the center point.

Depending on the edit mode, this function either inserts the new structure element directly after the element indicated by the pointer or replaces the element indicated by the pointer. The pointer then points to the new elliptical arc 3 element.

During structure traversal, Digital PHIGS generates an elliptical arc from the start angle to the end angle, in a counterclockwise direction. Digital PHIGS binds the current values of the polyline primitive as defined in the PHIGS traversal state list to the primitive, and renders it according to the current curve approximation criteria.

If the magnitudes of both axes are less than or equal to 0, Digital PHIGS displays a dot. If one of the axes is less than or equal to 0, Digital PHIGS displays a line of the correct magnitude. If the axes do not define the system (the vectors are parallel and nonzero), Digital PHIGS uses (1,0,0) for the major axis and (0,1,0) for the minor axis.

If Digital PHIGS is in immediate mode, it performs this function immediately, but the function does not create a structure element.

Museum

pe_elliptical_arc3(3g) — Subroutines

Name

Syntax

Data Structures

Description

See Also