CS 445: Exam 1 Review, Fall 2017

Exam 1 will be Wednesday, Oct. 4, 2017. It will be closed notes, closed book, and no electronic devices are allowed. Paper and pencil only.

Topics

• Highly Recommended: Work through the old exams (with paper and pencil) without looking at the solutions.

• WebGL Pipeline, Structure & Setting up the geometry

  • GPU vs CPU
  • What are Vertex Buffer Objects (VBOs) and why are they used?
  • Geometry Primitives: GL_POINTS, GL_LINES, GL_TRIANGLE, GL_TRIANGLE_FAN
  • OpenGL Primatives and what is their relationship to the data that gets put in the points() and colors() arrays (eg. on the Cube class).
  • How are the points generated, e.g. for the Disk class.
  • z-buffer
  • polygon meshes
  • Rendering pipeline
  • Rasterization
  • Vertex attributes vs uniform variables

• Geometric Objects and Transformations

  • Coordinate systems - right/left handed
  • Scalars, Points and Vectors - what are they and what operations are allowed between them?
  • Vectors: representation, length, addition, scalar multiplication, dot products, cross products.
  • Matrix Operations: multiplication, addition, transpose, inverse (of standard transformations such as rotations, translations,scale), identity.
  • 3D Transformations: Translation, Scale, Rotation, Reflection, Projection.
  • Composition of transformations.
  • Homogeneous coordinates. What are they, why are they used?
  • How 3D Transformations are applied in webgl using the "modelview" matrix and matrix stack. What happens when you push and pop the stack. What does the stack contain at each step in the code.
  • What are Euler angles? What is gimbal lock and when does it occur?

• Scene graphs - be able to create the scene graph for a particular structure (car, robot, robotic arm, ...)

  • Draw picture of object with lengths, angles, type of movement, etc.
  • Draw the associated scene graph with the precise transformations identified.
  • Implement the sequence of "opengl operations" (using RotateX(theta), RotateY(theta), RotateZ(theta), Translate(x,y,z), Scale(x,y,z), PushMatrix, PopMatrix). You don't need to know the exact syntax but the type and order of the operations is important.

• Transformation Pipeline

  • Pipeline: Understand what the different stages of the pipeline do: geometry pipeline (also see pipeline).
  • View Matrix, V:
    • Calculating the view matrix: V = viewRotation * Translate( -eye )
    • "eye" is the location of the camera in the WCS
    • Calculating u, v, n for the camera. Use these to create the viewRotation matrix. Also see Coordinate Transform Notes
  • Modelview Matrix: Coordinate transformations of a point: Object Coordinates (OCS) to World Coordinates (WCS) to Camera Coordinates (CCS):
    • The Modelview matrix is the product of the view matrix, V, and the model transforms M (e.g. obtained from the scene graph). See picture
    • Also see Coordinate Transform Notes
  • Projection and Viewport Transformations:
    • What is the view volume or Frustum? Orthographic vs Perspective.
    • What is the purpose of the projection transformation? How does it change the frustum? See picture.
    • What is the purpose of the viewport transformation? See picture.
    • See notes and the methods in mat.h: Ortho(), Frustum(), Perspective().
    • What is the Perspective Division? Why is it separated out from the projection transformation?
    • What is rasterization?

• Controls for Navigation through a scene

  • Fly through transformations. See your code from Lab 4.
  • Tumble, track (pan), dolly (zoom) - For tumble, see Coordinate Transform Notes

---