INTRODUCTION TO NODEPATHS

A nodepath is a mathematical entity that allows you to distinguish between multiple occurrences of the same node due to instancing. This allows you to indicate a specific occurrence of a node in the scene graph. There are two things you can do with nodepaths:

• Perform intersection tests between specific nodepaths and other nodes in the scene graph
• Pick graphical entities rendered into the WTK window. The WTK picking functions generate the nodepath of a picked geometry node.

figure 19

 

In figure 19 two nodepaths can be generated so that when picking you can pick the spheres.

Creating Nodepaths

WTnodepath_new

Use this function to create a new nodepath. A nodepath is fully specified by giving the bottom-most node in interest, the ancestor node, and the occurrence number.

SYNTAX:

WTnodepath_new(WTnode *node, WTnode *ancestor, int which);

ARGUMENTS:

node -- bottom-most node
ancestor -- The ancestor
which -- The occurrence of the node.

RETURN TYPE:

Returns a pointer to a new WTnodepath

Picking

WTK provides functions to allow the user to pick a geometry in the render window using a pointing device such as the mouse. The WTwindow_pickpoly function allows the user to specify a 2d screen coordinate and will pick the front-most polygon the appears beneath that point.. You can obtain the 2d screen point by using the mouse raw data structure and miscellaneous data structure.

 

Getting the Mouse Data

All sensors have miscellaneous and raw data structures that information returned by the sensor. In the case of the mouse, the miscellaneous data structure contains information about which button has been pressed on the mouse, and the raw data structure will contain the 2d screen coordinate of where the mouse is currently in the window. Use the functions WTsensor_getrawdata and WTsensor_getmiscdata to obtain this information

WTsensor_getmiscdata

Use this function to obtain the miscellaneous information associated with a sensor. In the case of the mouse button press information is contained in the miscellaneous data structure.

SYNTAX:

int WTsensor_getmiscdata(WTsensor *sensor);

ARGUMENTS:

sensor -- A pointer to a type WTsensor to get the misc. data from.

RETURN TYPE:

integer containing the miscellaneous data. In the case of the mouse it will be one of the predefined constants

WTMOUSE_LEFTBUTTON

WTMOUSE_LEFTDOWN

WTMOUSE_LEFTUP

WTMOUSE_RIGHTBUTTON

WTMOUSE_RIGHTDOWN

WTMOUSE_RIGHTUP

WTMOUS_MIDDLEBUTTON

WTMOUSE_MIDDLEDOWN

WTMOUSE_MIDDLEUP

EXAMPLE: -- Getting mouse clicks. This example assumes that you have a sensor object called mouse that has been initialized with the WTmouse_new function.

…..

if(WTsensor_getmiscdata(mouse) & WTMOUSE_LEFTBUTTON)

WTmessage("Left button pressed");

…..

Notice the we use a bitwise and operator (&) to test for the comparison.

WTsensor_getrawdata

Use this function to obtain the rawdata structure associated with a sensor. For the mouse the current 2d screen coordinate will be contained in the rawdata structure.

SYNTAX:

void *WTsensor_getrawdata(WTsensor *sensor);

ARGUMENTS:

sensor -- A pointer to the sensor in question

RETURN TYPE:

The sensor specific raw data structure. The return needs to be typecast appropriately before the contents of the structure can be accessed.

EXAMPLE -- Getting 2D mouse points. This example assumes that you have a sensor object called mouse that has been initialized with the WTmouse_new function.

….

WTmouse_rawdata *rawdata;

if(WTsensor_getmiscdata(mouse) & WTMOUSE_LEFTBUTTON)

rawdata = (WTmouse_rawdata)WTsenosr_getrawdata(mouse);

….

Assignment 17

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
• Create a global flag that will be set TRUE when in pickmode.
• Create a mouse handler function that is called from the action function when pickmode the FLYMODE flag is set FALSE.
• The mouse_handler function should find out if the left or right mouse button was pressed and obtain the 2d screen coordinate and print it to the console window
• Move all the keyboard interaction code into its own function called handle_key. This function should only be called from the action function of a key were pressed on the keyboard. As an argument is should receive the value of the key pressed and return TRUE if the key was acted upon otherwise is should return FALSE.
• 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)
• Set the rgb color of the sphere to red (255,0,0)
• Set the rgb color of the cylinder to blue (0,0,255)
• Set the rendering style of the sphere geometry to wireframe.
• Attach to two spheres to the cylinder
• Prebuild all the geometries
• Zooms the view in the window
• Create a task function that is associated with the node containing the cylinder. The function should rotate the cylinder in its parent reference frame around the Y axis by 15 degrees each time through the simulation loop.
• Add the mouse to the universe as a sensor
• Attach the mouse to the viewpoint using a motionlink
• Read a file called lights into the universe. Make sure the file is located in the current working directory.
• Load the material table name wtmatlib.mat. (make sure you include the wtmatlib.h header file into your program) This header file contains define statement that relate a color name to an index number in the wtmatlib.mat file.
• Have all geometries reference that material table file
• Set the material table index for the cylinder to PURPLE
• Set the material table index for the spheres to RED
• 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
  • press I to obtain the extents, midpoint, and radius of each geometry.
  • press t to translate the spheres and cylinder along their local X axis.
  • Create a function that uses the WTnode_translate function and takes as an argument the node to translate, three floating point values for the translation values, and the frame in which to translate.
  • Press f on the keyboard to toggle the motionlink from enabled to disabled and disabled to enabled. You should also print a message to the user indicating weather they are in pick or navigation mode.
  • This should also toggle the flymode flag.
  • Press a on the keyboard to decrease the default ambient light value in the universe
  • Press A on the keyboard to increase the default ambient light value in the universe
  • Move all the keyboard interaction into its own function called handle_key.
  • The user should be informed of the current ambient light level in the universe.

Picking graphical objects

WTK allows the user to get the polygon that is the front-most polygon under a 2ds screen point.

WTwindow_pickpoly

Use this function to get a pointer to a WTpoly that is the front-most polygon under the 2d coordinate passed in.

SYNTAX:

WTpoly *WTwindow_pickpoly(WTwindow *win, WTp2 screenpoint, WTnodepath *nodepath, WTp3 point3d);

ARGUMENTS:

window -- A pointer to a type WTwindow that the poly is in
screenpoint -- A WTp2 containing the 2d screen coordinate
nodepath -- A pointer to a nodepath that will receive the information concerning what node was picked. You can pass NULL to this argument and WTK will not figure out the nodepath for you.
Point3d -- A 3d point in world coordinates at which the selected poly was intersected.

RETURN TYPE:

A pointer to the WTpoly that was picked

Getting the graphical object from the nodepath

WTnodepath_getnode

Use this function to access the nodes of a nodepath.

SYNTAX:

WTnode *WTnodepath_getnode(int num);

ARGUMENTS:

num -- the number of the node in the nodepath. To get the bottommost node pass in WTnodepath_numnodes() - 1;

RETURN TYPE

A pointer to a type WTnode containing the node information.

EXAMPLE:

….

WTmouse_raw *rawdata;

WTnodepath *nodepath[1];

WTp3 point3d;

WTnode *pickednode;

if(WTsensor_getmiscdata(mouse) & WTMOUSE_LEFTBUTTON)

rawdata = (WTmouse_rawdata)WTsenosr_getrawdata(mouse);

WTwindow_pickpoly(WTuniverse_getcurrwindow(), rawdata, nodepath, point3d);

pickednode = WTnodepath_getnode(nodepath[0], WTnodepath_numnodes(nodepath[0]) - 1);

WTnode_boundingbox(pickednode, TRUE);

….

Assignment 18

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 second sphere just like the one created above.
• Create a movable geometry node for the cylinder whose parent is the root node.
• Create a movable geometry node for the sphere whose parent is NULL.
• Change your instance of a the sphere to a regular node whose parent is NULL
• Use WTmovnode_attach to attach the two spheres to the cylinder
• Create a new global flag called SPINFLAG that is initially set to FALSE
• Create a global flag that will be set TRUE when in flymode.
• Create a mouse handler function that is called from the action function when pickmode the FLYMODE flag is set FALSE.
• Modify the mouse_handler function to return a pointer to a type WTpoly.
• Add functionality to the mouse handler that will pick a polygon with the right mouse button and a node with the left mouse button. If a node is picked turn on the bounding box for that node. if a polygon is picked set its material table index to WHITE. Use the WTpoly_setmatid function and WTpoly_getmatid functions. If a new node is picked the old selected nodes bounding box should be shut off and if a new poly is picked its material table index should be set back to the original index number it had before it was picked. You SHOULD NOT be able to have both a node and a polygon highlighted at the same time.
• Make sure that your mouse handler returns a pointer to the polygon obtained with WTwindow_pickpoly
• Move all the keyboard interaction code into its own function called handle_key. This function should only be called from the action function of a key were pressed on the keyboard. As an argument is should receive the value of the key pressed and return TRUE if the key was acted upon otherwise is should return FALSE.
• 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)
• Set the rgb color of the sphere to red (255,0,0)
• Set the rgb color of the cylinder to blue (0,0,255)
• Set the rendering style of the sphere geometry to wireframe.
• Attach to two spheres to the cylinder
• Prebuild all the geometries
• Zooms the view in the window
• Create a task function that is associated with the node containing the cylinder. The function should rotate the cylinder in its parent reference frame around the Y axis by 15 degrees each time through the simulation loop.
• Add the mouse to the universe as a sensor
• Attach the mouse to the viewpoint using a motionlink
• Read a file called lights into the universe. Make sure the file is located in the current working directory.
• Load the material table name wtmatlib.mat. (make sure you include the wtmatlib.h header file into your program) This header file contains define statement that relate a color name to an index number in the wtmatlib.mat file.
• Have all geometries reference that material table file
• Set the material table index for the cylinder to PURPLE
• Set the material table index for the spheres to RED
• 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
  • press I to obtain the extents, midpoint, and radius of each geometry.
  • press t to translate the spheres and cylinder along their local X axis.
  • Create a function that uses the WTnode_translate function and takes as an argument the node to translate, three floating point values for the translation values, and the frame in which to translate.
  • Press f on the keyboard to toggle the motionlink from enabled to disabled and disabled to enabled. You should also print a message to the user indicating weather they are in pick or navigation mode.
  • This should also toggle the flymode flag.
  • Press s on the keyboard to toggle the value of SPINFLAG
  • Press a on the keyboard to decrease the default ambient light value in the universe
  • Press A on the keyboard to increase the default ambient light value in the universe
  • Move all the keyboard interaction into its own function called handle_key.
  • The user should be informed of the current ambient light level in the universe.
  • In the action function if SPINFLAG is TRUE rotate the cylinder around its local Y axis by PI divided by 4 (PID4)