Introduction to WTK Sensors

• In WTK sensor objects generate position, orientation, and other types of data by reading inputs which originate in the real world. These inputs can be used to control the motion and other behavioral aspects of objects in the simulation. Using sensors and motionlinks the user can be directly coupled the viewpoints, graphical objects, and lights in the universe.
• WTK supports may of the 2d, 3d, and 6d (position/orientation) sensors on the market today. Some sensors return relative values (displacement or deltas) while other sensors return absolute position/and orientation values. Regardless of what WTK receives from the sensor it works with relative coordinates or displacements for the last position/orientation.
• WTK supports the follow sensors:
  • Standard mouse
  • Spaceball
  • Spaceball Space Controller
  • Geoball
  • Isotrak, IsotrakII, Fastrak, and Insidetrak
  • Bird, Extended range bird, and flock of birds
  • Logitech 3d mouse (red baron)
  • CrystalEyes and CrystalEyesVR
  • Fakespace BOOM
  • Magellan
  • Wayfinder
  • Virtual i-o head tracker
  • Thrustmaster serial FCS and WCS (serial joysticks)
  • Thrustmaster T2 steering wheel
  • CyberMaxx 2 head tracker
  • 5DT glove
  • Pinch glove
  • Cyberglove (SGI only)

   

• WTK also provides the ability to write your own sensor drivers that can be used with custom sensor devices or to alter the sensor drivers provided by Sense8

Sensor Construction and Destruction

WTK provides easy to use MACROS to allow the user to create sensor objects. These sensor objects are then stored in pointer to a WTsensor structure. Each sensor type supported by WTK has its own MACRO it construct the sensor. The following chart lists the sensor construction MACROS and the corresponding sensor they construct.

WTmouse_new

Creates a new sensor object with the mouse and adds it to the universe

SYNTAX:

WTsensor *WTmouse_new(void);

ARGUMENTS:

none

RETURN TYPE:

A pointer to a type WTsensor that hold the mouse object

WTiglasses_new

Creates a new sensor object with the virtual i-o iglasses head-tracker and adds it to the universe.

SYNTAX:

WTsensor *WTiglasses_new(unsigned char port);

ARGUMENTS:

port -- The serial port the sensor is attached to can be COM1, COM2, COM3, or COM4

RETURN TYPE:

A pointer to a WTsensor that contains the iglasses tracker

Understanding how a sensor driver works

• WTK sensor drivers are written to allow the user to access information such as absolute coordinates and button presses for sensors depending on the sensor. WTK also provides the user with the ability to change how the data read from the sensor is interpreted by allowing the user to create their own update functions. To understand this we must first understand how a sensor driver works
• Sensor drivers written of WTK consist of three major functions, an "open" function, close function and update function.

Sensor open functions

Open functions open communication with the sensor and are called only once when the sensor is constructed with a call to one of the sensor MACROS. The generally ready the sensor for communication and obtain the first record from the sensor. If the sensor returns data as absolute positions and orientations then this record is stored for later use to create a relative record.

Sensor close functions

Close function break communication with the sensor and reset any system parameters that may have been changed. They are called only once when either the sensor object is destroyed or when the universe exits

Sensor update functions

These functions are the work horses of the sensor drivers. They are called once each time through the simulation loop for each sensor that is in the universe. The obtain a record form the sensor, weather it be position/orientation record or button presses. If the record is in absolute position/orientations the record is "reletivized" in this function and the set so that WTK’s simulation manager can use the values to update any viewpoints, objects, or lights that might be attached to the sensor via motionlinks.

A sensors update function can be set by the user with a call to WTsensor_setupdatfn. This will tell WTK to use the function passed in to update the sensor passed in.

Assignment 11

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)
• 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.
• 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
• 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.