INTRODUCTION TO MOVABLE NODES

Creating objects and isolating them from each other can be a lengthy process. WTK R6 recognized the need to simplify the process so the movable node was created for this purpose. A movable node is a combination or package of three different nodes a separator node or transform separator node, a transform node, and a content node.

• Separator and Transform Separator -- Block information from propagating back up the scene graph tree
• Transforms -- add translation and orientation information to the state of the scene graph
• Content -- Can be one of the following types of nodes:
  • Geometry
  • Lights
    • Point
    • Directed
    • Spot
  • Separator
  • Switch
  • LOD
• Any of the node manipulation and property functions can be used with movables i.e. WTnode_settranslation and WTnode_setname

Creating Movables

The following is a list of the movable creation functions and the type of content node they create

WTmovgeometrynode_new

Creates a new movable node with a separator and geometry as its content and adds it as the last child of the parent specified.

SYNTAX:

WTmovgeometrynode_new(WTnode *parent, WTgeometry *geom);

ARGUMENTS:

parent -- The parent node
geom -- The geometry to use in the content node

RETURN TYPE:

A pointer to a type WTnode that contains the movable information.

Instancing a movable node

In order to make an instance of a movable node there is a function provided WTmovnode_instance. You may have multiple instances of movable nodes in a scene graph. Since a movable node contains a transform node it would not be possible to have instances of a movable node where each instance has its own position and orientation information unless a special function were created to handle this case. If multiple instances of a movable node are desired then this function will all the user to create multiple instances and yet do it in an as efficient a manner as possible because all of the information stored in the movable (except for the transform ) is shared by every instance of the movable. In other words all information is shared but the transform but each instance has its own transform node.

WTmovnode_instance

This function creates an instance of a movable node and inserts it as the last child of the parent specified.

SYNTAX:

WTnode *WTmovnode_instance(WTnode *parent, WTnode *movable);

ARGUMENTS:

parent -- The parent node. If this argument is NULL then the node is created as an orphan that can be inserted later.
movable -- The movable node to create an instance of.

RETURN TYPE:

The new movable node. NULL if the movable argument is a regular node or an instance is not created

Assignment 7

project definition:

• Creates a universe with a bordered window in monoscopic mode..
• Create a cylinder that has a height of 40, a radius of 5, 12 tessellation lines, is single sided and gouraud shaded.
• Create a sphere with a radius of 10, 12 lat and long divisions, is single sided, and gouraud shaded.
• Create a movable geometry node for the cylinder whose parent is the root node.
• Create a movable geometry nodes for the sphere whose parent is the root node.
• Create and instance of the movable node containing the sphere as the 2^nd child of the root node
• Set the translation of the movable geometry containing the first sphere to (0,-20,0)
• Set the translation of the movable geometry containing the second sphere to (0,20,0)
• Zooms the view in the window
• Create an action function that allows the user to:
  • press q to quit
  • press p to print the scene graph from the root node. (use WTnode print)
• Print the scene graph, does it match your scene graph? If not, fix the bug.
• Can you see all the geometry?