NODE PROPERTIES

WTK functions provide access to three useful properties that describe the space occupied by the geometries in a scene graph.

figure 10

 

The following chart list the node property access functions

WTnode_getextents

The extents box of a node in a scene graph is relative to the coordinate system )the X, Y, Z axes) defined by the transformation accumulated by traversing the scene graph as far as that node. A node’s extents box encloses the geometries beginning at the specified node and including all children and grandchildren. These comprise the node and it’s sub-tree.

SYNTAX:

FLAG WTnode_getextents(WTnode *node, WTp3 extents);

ARGUMENTS:

node -- The node to retrieve the extents from
extents -- A WTp3 that will receive the extents information

RETURN TYPE:

Returns false if the node passed in cannot have children or it is not a geometry node itself

WTnode_getradius
The radius of a node is defined as the distance from the midpoint of the nodes extents box to one of its corners (see figure 10)

SYNTAX:

float WTnode_getradius(WTnode *node);

ARGUMENTS:

node -- The node in question

RETURN TYPE:

float that is the distance.

WTnode_getmidpoint

The midpoint of a node is the midpoint of the node’s extents box.

SYNTAX:

FLAG WTnode_getmidpoint(WTnode *node, WTp3 midpoint);

ARGUMENTS:

node -- The node in question
midpoint -- A WTp3 that will receive the midpoint information

RETURN TYPE:

Returns false if the node passed in cannot have children or it is not a geometry node itself.

Turning on a nodes bounding (extents) box

WTnode_boundingbox

This function is a toggle to turn on and off a nodes extents box. The color of the extents box can be set using the WTuniverse_setbbrgb function.

SYNTAX:

void WTnode_boundingbox(FLAG toggle);

ARGUMENTS:

toggle -- If this argument is TRUE then the bounding box is drawn. FALSE turns the bounding box off.

NOTE: Bounding boxes ore off by default.

RETURN TYPE:

Void

Assignment 8

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)
  • press i to obtain the extents, midpoint, and radius of each node
  • Hint: Use WTp3_print to print the values returned in the WTp3’s
  • Use WTmessage to print other values
    • WTp3_print(WTp3 p3, char *message);
    • WTmessage works just like ANSI C printf function