NODE CONSTRUCTION

• All nodes have constructor functions.
• To create a new geometry node from a geometry file you use WTgeometrynode_load.
• A very useful function from checking the scene graph is the WTnode_print utility function.

WTnode_print(WTnode *node);

• All node constructor functions have one argument that specifies the parent node to attach the node beneath. Root node constructor function does not take a parent argument since a root node can not have a parent.
• If the parent argument for a constructor function is set to NULL the node becomes an orphan that can later be inserted beneath the specified using the WTnode_addchild or WTnode_insertchild functions.
• All constructor functions return a pointer to a type WTnode
• The following is a list of the most commonly used constructor functions:

Loading a file into the Scene Graph

• WTK also provides function for loading in geometry and full scene graph descriptions from preexisting files. This is probably the most common way to load geometry into the scene
• The following is a list of the functions provided for this purpose.
  
• WTnode_load
  • This function allows the user to create one or more nodes from data read in from a file. It automatically adds these nodes to the scene graph beneath the specified parent node. The data read in from the file may contain geometry or any data which corresponds to any of the supported node types.
  • A geometry node is created for each geometry contained in the file, and the node name assigned to each geometry node is the name of the corresponding geometry in the file.

  SYNTAX:

  WTnode *WTnode_load(WTnode *parent, char *filename, float scale);

  ARGUMENTS:

  • parent -- specifies the parent node to insert beneath. If the argument is NULL the nodes become "orphan nodes" that can later be inserted using addchild or insertchild function.
  • filename -- specified the filename to read. Valid file types are NFF, BFF, DXF, 3DS, OBJ, FLT,GEO, SLP, .WRL
  • scale -- the amount to scale the geometry along each axis. If no scaling is desired specify 1.0f for this argument.

  RETURN TYPE:

  • WTnode * -- a pointer to a type WTnode. If the nodes in the file are arranged into a hierarchical fashion, then the topmost node is returned. If the nodes are arranged in a "flat" (non-hierarchical) file then the first node that was loaded is returned.
    
    
• WTgeometrynode_load
  • This function creates a single geometry mode from the data read in from a file, and adds the newly created node as the last child node of the parent you specify

SYNTAX:

WTnode *WTgeometrynode_load(WTnode *parent, char *filename, float scale);

ARGUMENTS:

parent -- The parent to insert beneath. If the argument is NULL the nodes become "orphan nodes" that can later be inserted using addchild or insertchild function.
filename -- The name of the file to that contains the geometric data. Supported types include NFF, BFF, DXF, 3DS, OBJ, GEO, SLP. These file types may contain more than one geometry in which case all the geometry is loaded in a single geometry. You CANNOT use this function to load FLT, or WRL files since these files can contain non-geometric information.
Scale -- The amount to scale the geometry on all axes. If no scaling is desired you should specify 1.0f as this argument.

Extra Zooming the Window

The function WTwindow_zoomviewpoint( WTwindow *window) will zoom the window so that all the geometry contained in that window is in view.

Assignment 2

Project definition: Write an application that performs the following functionality:

• Creates a universe with a borderless window in monoscopic mode.
• Sets the universe rendering type to wireframe.
• Load the file "oplan" as a single geometry in a node beneath the root node
• 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)
• Hint: you will need to use the WTwindow_zoomviewpoint function in order to see all of the geometry in the file.
• Use one of the universe class functions to obtain the WTwindow parameter for the zoom function.
  
  
  

Creating geometry "on the fly"

• WTK allows the user to create geometries on the fly use geometry primitive construction functions. Notice the function WTnode *WTgeometrynode_new(WTnode *parent, WTgeometry *geom); takes as its second parameter a type WTgeometry.
• There is a unique one to one relationship between the data that is used to construct the geometry and the geometry node. Every geometry node MUST have a geometry associated with it. The function WTgeometrynode_load performs this functionality for you by reading the data from a file and associating it with a node of type geometry. If you create geometries on the fly you must perform this functionality yourself. Note this one to one relationship between the geometry and its node prevents the user from making instances of geometry data, however you are able to make an instance of a geometry node. The following is a guideline to follow when creating geometries on the fly.
  • Create the geometry using one of the geometry creation methods
  • Associate the geometry with a node using the WTgeometrynode_new function.

Creating Primitives

When creating primitives it is important to note that all primitives are constructed using their local coordinate system (0,0,0) being the center or midpoint of the geometry. Therefore when the geometry is inserted into the scene graph it is inserted about the World (0,0,0). Refer back to the Understanding coordinate system sections for more information on coordinate systems. WTK provides functions for creating the following primitive types:

NOTE: When a primitive is create it is assigned a default material of matte white.

WTgeometry_newblock

SYNTAX:

WTgeometry *WTgeometry_newblock(float lx, float ly, float lz, FLAG bothsides);

ARGUMENTS:

lx -- length in the x direction
ly -- length in the y direction
lz -- length in the z direction
bothsides -- indicates whether polygons backfaces are visible.

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL if unsuccessful.

WTgeometry_newcylinder

SYNTAX:

WTgeometry *WTgeometry_newcylinder(float height, float radius, int tess, FLAG bothsides, FLAG gouraud);

ARGUMENTS:

height -- height along the world y axis
radius -- radius of the cylinder
tess -- the number of lines used to define the curved surface of the cylinder (the sides)
bothsides -- indicates whether polygons backfaces are visible.
Gouraud -- outward pointing vertex normals parallel to the cylinder base are defined. (on systems that support gouraud shading)

RETURN TYPE:

A pointer to a type WTgeometry if successful NULL if unsuccessful.

WTgeometry_newcone

SYNTAX:

WTgeometry *WTgeometry_newcone(float height, float radius, int tess, FLAG bothsides);

ARGUMENTS:

height -- the height of the cone along the world Y axis
radius -- the radius of the cone
tess -- the number of lines used to represent the curved surface of the cone
bothsides -- indicates whether polygons backfaces are visible.

RETURN TYPE:

A pointer to a type WTgeometry if successful NULL if unsuccessful

WTgeometry_newsphere

SYNTAX:

WTgeometry *WTgeometry_newsphere(float radius, int nlat, int nlong, FLAG bothsides, FLAG gouraud);

ARGUMENTS:

radius -- the radius of the sphere
nlat -- the number of lines used to represent the curved surface along the latitude of the sphere
nlong -- the number of lines used to represent the curved surface along the longitude of the sphere
bothsides -- indicates whether polygons backfaces are visible.
Gouraud -- define outward pointing vertex normals

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL in unsuccessful

WTgeometry_newhemisphere

SYNTAX:

WTgeometry *WTgeometry_newhemisphere(float radius, int nlat, int nlong, FLAG bothsides, FLAG gouraud);

ARGUMENTS:

radius -- the radius of the sphere
nlat -- the number of lines used to represent the curved surface along the latitude of the sphere
nlong -- the number of lines used to represent the curved surface along the longitude of the sphere
bothsides -- indicates whether polygons backfaces are visible.
Gouraud -- define outward pointing vertex normals

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL in unsuccessful

WTgeometry_newrectangle

SYNTAX:

WTgeometry *WTgeometry_newrectangle(float height, float width, FLAG bothsides);

ARGUMENTS:

height -- length along the world y axis
width -- length along the world x axis
bothsides -- indicates whether polygons backfaces are visible.

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL if unsuccessful

WTgeometry_newtruncone

SYNTAX:

WTgeometry *WTgeometry_newtruncone(float height, float toprad, float baserad, int tess, FLAG bothsides, FLAG gouraud);

ARGUMENTS:

height -- height of the cone along the world Y axis
toprad -- the radius of the top of the cone
baserad -- the radius of the base of the cone
tess -- the number of lines used to represent the curved surface of the cone
bothsides -- indicates whether polygons backfaces are visible.
gouraud -- outward pointing normals for the side polygons are defined

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL if unsuccessful

WTgeometry_newextrusion

SYNTAX:

WTgeometry *WTgeometry_newextrusion(WTp2 points[], int numpts, float height, FLAG bothsides, FLAG gouraud);

ARGUMENTS:

points[] -- an array of points that is assumed to be NON-SELF INTERSECTING contour in the x-z plane of the world coordinate system. The number of points must be between 3 and 256 and are 2 dimensional (WTp2)
numpts -- the number of points in the points array
height -- the height to extrude along the world y axis
bothsides -- indicates whether polygons backfaces are visible.
gouraud -- outward pointing normals for the side polygons are defined

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL if unsuccessful.

WTgeometry_new3dtext

SYNTAX:

WTgeometry *WTgeometry_new3dtext(WTfont3d *font, char *string);

ARGUMENTS:

font -- A pointer to a type WTfont3d (obtained for the WTfont3d_load function)
string -- the string to print such as "Hello"

RETURN TYPE:

A pointer to a type WTgeometry if successful, NULL is unsuccessful

Associating the geometry with a node

Once the geometry is created it is not visible on the screen because it has not been associated with a node in the scene graph. There are two functions that will do this WTgeometrynode_new and WTmovgoemetrynode_new. The second function deals with movables so that well learn about later. For now we will use WTgeometrynode_new.

WTgeometrynode_new

SYNTAX:

WTnode *WTgeometrynode_new(WTnode *parent, WTgeometry *geom);

ARGUMENTS:

parent -- the new node is inserted as the last child of the parent specified. If the parent argument is NULL then the node is an orphan and can be inserted or added later.
geom -- A pointer to a type WTgeometry obtained with one of the primitive construction functions.

RETURN TYPE:

A pointer to a type WTnode.

Assignment 3

Project definition: Write an application that performs the following functionality:

• Creates a universe with a bordered window in monoscopic mode..
• Create a cylinder that has a height of 20, a radius of 5, 12 tessellation lines, is single sided and gouraud shaded.
• Create a spheres with a radius of 10, 12 lat and long divisions, is single sided, and gouraud shaded.
• Create a geometry node for the cylinder whose parent is the root node.
• Create 2 geometry nodes for the spheres whose parent is the root node.
• 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? Why not?

Node instances

• WTK allows the user to create an efficient database by providing the ability to create "instances" of nodes instead of complete copies. In Exercise 3 you created 2 sphere geometries and then created 2 geometry nodes from them. It would be much more efficient to have created a single sphere associated it with a node and then instanced that geometry node there by referencing the same node twice in the scene graph so our scene graph would look something like this:

figure 9

• To create an instance of a node create the node and then use WTnode_addchild or WTnode_insertchild to with the node pointer to create the instance.

WTnode_addchild

Add a node as the last child of the parent specified

SYNTAX:

FLAG *WTnode_addchild(WTnode *parent, WTnode *child);

ARGUMENTS:

parent -- The parent node for the node
child -- The child node to add

RETURN TYPE:

FLAG tells if the function was successful.

WTnode_insertchild

Adds a node as the numth child of the parent node specified

SYNTAX:

FLAG WTnode_insertchild(WTnode *parent, WTnode *child, int childnum);

ARGUMENTS:

parent -- The parent node to insert beneath
child -- The node to insert
childnum -- the number child to insert

RETURN TYPE:

FLAG indicating success of failure.

Assignment 4

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 geometry node for the cylinder whose parent is the root node.
• Create a geometry nodes for the sphere whose parent is the root node.
• Create and instance of the sphere as the 2^nd child of the root node
• 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? Why not?

   

Creating transform and separator nodes

In order to move objects in the simulation you must first create a transform node that will apply a transformation to the graphical object, but these functions only work on transform or movable nodes. First a transform node must be created.

WTxformnode_new

SYNTAX:

WTnode *WTxformnode_new(WTnode *parent);

ARGUMENTS:

parent -- The node will be inserted as the last child of the parent specified. If NULL is specific as the parent argument then the node is created as an "orphan" and can be added or inserted later.

RETURN TYPE:

A pointer to a type WTnode containing the new transform node.

Setting the contents of the transform node

Once the transform node is created its contents must be set. Transformations in WTK are stored in 4x4 matrices the specify the rotation and translation the will be applied to the state of the scene graph. There are functions that allow the user to set the absolute contents of transform nodes. The following chart lists these function and gives a brief explanation of their use

WTnode_settranslation

Replaces the translation component or the transformation matrix of the specified node.

SYNTAX:

FLAG WTnode_settranslation(WTnode *node, WTp3 txvector);

ARGUMENTS:

node -- The node to operate on. This can only be a transform or movable node.
txvector -- the vector specifying the magnitude of the translation.

RETURN TYPE:

FLAG indicating the success of the function.

WTnode_setrotation

Replaces the rotational component of the specified nodes transformation matrix.

SYNTAX:

FLAG WTnode_setrotation(WTnode *node, WTm3 rotation);

ARGUMENTS:

node -- The node to operate upon.
rotation -- a 3x3 matrix specifying the rotation to apply

RETURN TYPE:

FLAG indication the success of the function

WTnode_setorientation

Replaces the rotational component of the specified nodes transformation matrix

SYNTAX:

FLAG WTnode_setorientation(WTnode *node, WTq orientation);\

ARGUMENTS:

node -- The node to operate upon
orientation -- a WTq specifying the rotation as a quaternion

RETURN TYPE:

FLAG indicating the success of the function.

WTnode_settransform

Replaces the entire transformation matrix of the specified node.

SYNTAX:

FLAG WTnode_settransform(WTnode *node, WTm4 matrix);

ARGUMENTS:

node -- the node to operate upon.
matrix -- The 4x4 matrix specifying the transform (translation and rotation) information.

RETURN TYPE:

FLAG indicating the success of the function

Assignment 5

project definition:

• Create a universe with a bordered window in monoscopic mode..
• Create a cylinder that has a height of 40, a radius of 5, 112 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 geometry node for the cylinder whose parent is the root node.
• Create a geometry nodes for the sphere whose parent is the root node.
• Create and instance of the sphere as the 2^nd child of the root node
• Use a transform node to translate the geometry in the first cylinder 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? Why not?

Using a separator

In the previous assignment (assignment 5) both spheres were translated by the transform node. This is not the desired results. Only the first sphere should be translated. Using a separator node will allow the user to move graphical objects individually and not have the state set by the transform node affect other objects in the scene graph. As you recall there are two types of separator nodes separators and transform separators.

• Separators block all state information from propagating back up the scene graph tree
• Transform separators allows lighting state the "trickle" back up the scene graph tree.

WTsepnode_new

Creates a new separator node and adds it as the last child of the parent specified. If NULL is specified as the parent argument then the node is created as an orphan that can be added or inserted later.

SYNTAX:

WTnode *WTsepnode_new(WTnode *parent)

ARGUMENTS:

parent -- The parent node

RETURN TYPE:

A pointer to a type WTnode that hold the separator node.

WTxformsepnode_new

Creates a new transform separator and adds it as the last child of the parent specified. If NULL is specified as the parent argument then the node is created as an orphan that can added or inserted later.

SYNTAX:

WTnode *WTxformsepnode_new(WTnode *parent);

ARGUMENTS:

parent -- The parent node

RETURN TYPE:

A pointer to a type WTnode holding the transform separator.

Assignment 6

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 geometry node for the cylinder whose parent is the root node.
• Create a geometry nodes for the sphere whose parent is the root node.
• Create and instance of the sphere as the 2^nd child of the root node
• Use a transform node to translate the geometry in the first cylinder to (0,-20,0)
• Use a separator node to isolate the affects of the transform node.
• Create another transform node to translate the second sphere to (0,20,0)
• Create another separator node to isolate the effects of the second transform from the rest of the scene graph.
• 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? Why not?