3D VIEWING ILLUSTRATED

WHAT YOU SEE DEPENDS ON YOUR POSITION In the real world, what you see depends on where you stand, the direction you look, how you tilt your head, and so on.

3D VERSUS 2D In 3D, the y-axis typically points up instead of down. Negative coordinates, which are rarely used in 2D, are quite common in 3D. Because of this, the origin is at the center of space as opposed to the top-left corner as in 2D

MAJOR DIFFERENCES BETWEEN 2D AND 3D

RIGHT HANDED COORDINATE SYSTEM

CAMERA POSITION Camera positioned at (5, 5, 5): Looking at the southeast side

SOUTHWEST SIDE Move the camera to position (-5,5,5): Looking at the southwest side

LOOKDIRECTION The lookdirection is a vector that tells the camera where to look. For the camera below the lookdirection is (-1,-1,-1):

MOVING THE CAMERA Moving the camera does not change the lookdirection:

THE LOOKDIRECTION IS BASED ON A LOOKAT POINT Changing the lookdirection:

LOOKAT AND LOKDIRECTION The easiest way to determine the lookdirection is specify a lookat point in the scene and subtract the camera position from it: lookat – camera position For the above camera position, if the lookat is (0,0,0), then look direction is: Lookdirection = (0,0,0) – (-5,5,5) = (5, -5, -5)

SOUTHWEST VIEW Given an orthographic camera and the above lookdirection we get the following scene:

THE UP DIRECTION The lookdirection is not enough to get the correct view:

UP DIRECTION NOT CHANGED

UP DIRECTION WRONG

CORRECT

TRANSFORM UP DIRECTION

UP DIRECTION ANALOGY if you're designing a flight simulator, up is the direction perpendicular to the plane's wings, from the plane toward the sky when the plane is on the ground.

DEFAULT CAMERA POSITION

ROTATING THE CAMERA We will call rotation around the look vector (or z axis) Roll. Rotation around the up vector (or y axis) is called Yaw. Rotation around the Right vector (x axis) is called Pitch. Below is a picture of an aircraft showing roll, pitch and yaw in terms of the aircraft's local axis. Note: we can use a similar system for our object rotations

ROLL, PITCH AND YAW