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Cylinder_modeller(modeller) LYMB Cylinder_modeller(modeller)

NAME

cylinder_modeller - a geometric representation of a cylinder

DESCRIPTION

The cylinder_modeller class implements a geometric representation of a cylinder. It allows the user to manipulate a cylinder without seeing the details of its internal representation. The cylinder_modeller can be rendered directly on the graphics display. The default cylinder has a radius and height of 1.0, and is centered at the origin. It is oriented along the y-axis. The 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

modeller

INSTANCE VARIABLES

num_vertices The number of vertices in the cylinder geometry.

num_polygons The number of polygons in the cylinder geometry. This is just the number of polygons on the cylinder's surface plus two more for the ends of the cylinder.

radius The radius of the cylinder

height The height of the cylinder

MESSAGES

num_vertices? Get the number of vertices. Although the class interface allows this value to be set, it should not be since it is a value computed by the cylinder_modeller when it builds itself.

num_polygons? Get the number of polygons. Like num_vertices, this value should not be set since it is computed by the cylinder_modeller when it builds itself.

open! Sends the geomtry to the rendering primitive.

renderer_name? Returns the suffix of the class name used to draw the model on the graphics display.

generate_data! Builds the geometric representation of the cylinder required by the rendering primitive.

return_data! Returns the data built by generate_data! instead of sending it to the rendering primitive. This allows another class in the system to use this geometry.

bounds? Returns the minimum and maximum x, y and z values of the cylinder's vertices. This is used by the inherited "bounding_box?" method.

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

radius[=?] Sets/Gets the radius of the cylinder. message.

height[=?] Sets/Gets the height of of the cylinder. message.

EXAMPLES

The following LYMB script creates two cylinder models, one with the default resolution of 1 (3 body polygons) and the other with a resolution of 20. In addition, the second cylinder uses the "height=" and "radius=" messages to tranform it into a very long, thin cylinder.

cylinder_modeller new: cylinder_model1;

cylinder_modeller new: cylinder_model2 resolution=20 height=10 radius=0.2 ;

actor new: prism modeller=cylinder_model1 ;

actor new: pencil modeller=cylinder_model2 ;