3D Graphics Programming with QuickDraw 3D 1.5.4

Disks

Figure 18 shows a disk.

Figure 18 A disk

Labels

ASCII: Disk
Binary: disk ( = 0x6469736B )

Data Format



 
Vector3D            majorRadius

Vector3D            minorRadius

Point3D             origin

Float32             uMin

Float32             uMax

majorRadius: The major radius of the disk.
minorRadius: The minor radius of the disk.
origin: The center of the disk.
uMin: Minimum parametric limit value, assuming parametrization of the angle between majorRadius and the vector from origin to the circumference. The value u = 0 corresponds to 0 radians, and u = 1 corresponds to 2 radians. This is used to create partial ellipses. Let pMin be the point on the boundary of the partial ellipse that corresponds to uMin , and pMax the point corresponding to uMax . Then only the following part of the disk is drawn: the part bounded by the partial ellipse from pMin to pMax , the vector from the origin to pMin , and the vector from the origin to pMax . For details, see the QD3D documentation or develop magazine, Dec. 96. Must be 0 in Version 1.5.
uMax: Maximum parametric limit value; see uMin above. Must be 1 in Version 1.5.
vMin: Minimum parametric limit value in v direction. v can be viewed as the parametrization of the vector from origin to the circumference, ranging from 0 at the origin to 1 at the edge. Must be 0 in version 1.5.
vMax: Maximum parametric limit value in v direction; see vMin above. Must be 1 in version 1.5.

DATA SIZE

0 or 52

Description

A disk is a two-dimensional object defined by an origin (that is, the center of the disk) and two vectors that define the major and minor radii of the disk. A disk may have the shape of a circle, ellipse, or other oval. Attributes may be assigned to the entire disk only.

Default Surface Parameterization

The default surface parameterization for a disk is as shown in Figure 18 .

Parent Hierarchy

Shared, shape, geometry.

Parent Objects

None.

Child Objects

Attribute set (optional).

Example



 
Disk (

    1   0   0           # majorRadius

    0   1   0           # minorRadius

    0   0   0           # origin

    0                   #uMin

    1                   #uMax

    0                   #vMin

    1                   #vMax

)

Default Size

For objects of size 0, the default is as in the previous example.