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Elliptical_cylinder_modeller(modeller)LYMBElliptical_cylinder_modeller(modeller)

NAME

elliptical_cylinder_modeller - a geometric representation of a cylinder with an elliptical base.

DESCRIPTION

The elliptical_cylinder_modeller class implements a geometric representation of a cylinder with an elliptical base. It allows the user to manipulate a cylinder without seeing the details of its internal representation. The elliptical_cylinder_modeller can be rendered directly on the graphics display. The default cylinder has a height of 1.0, and is centered at the origin. It is oriented along the y-axis. The elliptical_cylinder_model is a variable resolution modeller. By default it has a very coarse approximation to a cylinder, using only 3 rectangles for its sides. The resolution instance variable can be used to set the number of polygons used for the body of the cylinder. A value less than 3 results in three polygons.

SUPERCLASS

cylinder_modeller

INSTANCE VARIABLES

focal_length The distance between the focal points. By default, the foci are on the x axis and centered about the origin. The default focal_length is zero (i.e. a circle).

const_val The constant distance used to define the elliptical base. The base is defined to be the locus of points in the xz plane such that the sum of the distances from the foci is equal to const_val. By default, const_val is 1.

MESSAGES

In addition to those messages accepted by cylinder_modeller, the following messages are known to the elliptical_cylinder_modeller.

focal_length[=?] Set/get the focal length.

const_val[=?] Set/get the const_val instance variable. Get the number of polygons. Like num_vertices, this value should not be set since it is computed by the elliptical_cylinder_modeller when it builds itself.

calculate! Recomputes all the vertices and polygons of the cylinder according to the current value of "resolution", an inherited variable.

EXAMPLES

The following LYMB script creates an elliptical cylinder model and rotates a camera about it in space so that the geometry may be viewed.

elliptical_cylinder_modeller new: the_model resolution= 40 focal_length= 2.2 const_val= 2.5 height= 5 ;

actor new: the_actor color=(.2,.6,.6) modeller=the_model;

environment new: env variable="LYMB_RENDERER";

camera new: c1 position=(7,7,0) focal_point=(0.0,0.0,0.0) view_angle=45 on!;

light new: l1 position=(10,3,6) on!;

object # [env value?] new: aren actors=[actor instances?] cameras=[camera instances?] lights=[light instances?];

aren render!;

cue new: rotate duration=100 tick_actions="c1 azimuth:2;" ;

scene new: ascene cues=rotate duration=100 renderers=aren ;

ascene start!;