Chapter 5, Viewing

• So far we have looked at everything from a single location.
• and we have had a Direction of Projection
• We would like to have a movable camera.
  • Or we will need to transform the scene from World coordinates to camera coordinates.
  • Where the origin is a the Look at position.
  • And the the camera out the z-axis.
• We also want to change the projection.
  • Right now we are "dropping" the final z coordinate (after transformation)
  • This is a orthogonal projection
  • This is a view where parallel lines do not meet in the distance.
  • But angles are preserved.
  • But we probably want to change to a perspective projection
    • There is a center of projection
    • Objects that are further away appear smaller.
• We will use the vertex shader to accomplish these tasks.
• Once the elements of the model have been established in a world coordinate system, we wish to transform them to a camera coordinate system.
  • We first need to specify a camera location
    • Specify a camera location (x,y,z)
    • Specify a look at position(x,y,z)
    • Use these two to create a look at vector
  • But this only fixes a line along which we are viewing.
  • We can specify either a right or an up vector.
    • Up is the usual vector to specify
    • Cross the up with the look at to give us a right vector.
    • This will give us an orthogonal vector to the first two.
    • Cross the right with the look at, which will give us a new up.
    • Which is orthogonal to the look at - right plane
  • This forms the basis of the camera vector space in terms of the world vector space.
    • So I can use this as a transformation from the world coordinate system to the camera coordinate system.
    • If I remember my linear properly.
  • lookAt in MV.js
    • Takes a eye position, at position and an up position.
    • And returns the transformation matrix to change from world to camera .
• Demo