3D Graphics Programming with QuickDraw 3D 1.5.4

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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.