3D Graphics Programming with QuickDraw 3D 1.5.4

Cones

Figure 19 shows a cone.

Figure 19 A cone

Labels

ASCII: Cone
Binary: cone ( = 0x636F6E65 )

Data Format



 
Vector3D            orientation

Vector3D            majorRadius

Vector3D            minorRadius

Point3D             origin

Float32             uMin

Float32             uMax

Float32             vMin 

Float32             vMax

orientation: The orientation of the cone. This vector also specifies the height of the cone.
majorRadius: The major radius of the cone.
minorRadius: The minor radius of the cone.
origin: The origin (that is, the center of the base) of the cone.
uMin: Minimum parametric limit value for u. To understand u, first consider u for the ellipse determined by majorRadius and minorRadius . The value of u on this ellipse is parametrized by the angle between the major axis and the vector from the origin to the circumference of the ellipse. The value u = 0 corresponds to 0 radians, and u = 1 corresponds to 2 radians. The values uMin and uMax are used to create partial ellipses. The basic idea is that only the part of the ellipse between uMin and uMax is drawn. For such a particular partial ellipse, the partial cone can be thought of as the result of keeping uMin and uMax fixed but letting v vary through its admissible range. The result looks like a cone with a wedge taken out. For details, see the QD3D documentation or develop magazine, Dec. 96. Must be 0 in Version 1.5.
uMax: Maximum parametric limit value in u direction; see uMin above. Must be 1 in Version 1.5.
vMin: Minimum parametric limit value in v direction. v can be viewed as arc length parametrization of the orientation vector, ranging from 0 at the origin to 1 at the tip. If vMin is not 0, then a truncated cone shaped slice will be removed from the bottom of the cylinder. Must be 0 in Version 1.5.
vMax: Maximum parametric limit value in v direction; see vMin above. If vMax is less than 1, then a small cone will be chopped off the top of the original cone, resulting in a truncated cone. Must be 1 in Version 1.5.

DATA SIZE

0 or 64

Description

A cone is a three-dimensional object defined by an origin (that is, the center of the base) and three vectors that define the orientation and major and minor radii of the cone. A cap may be attached to the base of a cone. Attributes may be assigned to the cap and face of a cone, and also to the entire cone.

DEFAULT SURFACE PARAMETERIZATION

The default surface parameterization for a cone is as shown in Figure 19 .

Parent Hierarchy

Shared, shape, geometry.

Parent Objects

None.

Child Objects

Caps (optional), bottom cap attribute set (optional), face cap attribute set (optional), attribute set (optional). A cone must have a bottom cap in order to have a bottom cap attribute set. Use Caps ( Bottom ) to set a cap on the base of a cone.

Example



 
Container ( 

    Cone ( 

        0 1 0 # orientation

        0 0 1 # major axis

        1 0 0 # minor axis

        0 0 0 # origin

        0     # uMin

        1     # uMax

        0     # vMin

        1     # vMax

    )

    Caps ( Bottom )

    Container ( 

        BottomCapAttributeSet ( )

        Container (

            AttributeSet ( )

            DiffuseColor ( 1 0 0 ) 

        )

    )

    Container ( 

        FaceCapAttributeSet ( )

        Container (

            AttributeSet ( )

            DiffuseColor ( 0 0 1 )

        )

    )

)

See the note in "Cylinders" , for an explanation of cap attribute sets.

Default Size

For objects of size 0, the default is: