CS 445: Topics for Sept 30/Oct 2, 2014

• Labs:

  • Complete: Lab 2: Getting Started with OpenGL
  • Begin: Lab 3: Transformations

• Modeling (continued from last week)

  • For better space efficiency, one often uses indexing instead.
  • Complex models are generallymade using specialized software such as Maya, Blender, Zbrush, etc
  • Once can export to various file formats which store the geometry, e.g. obj (Wavefront) or stl (STereoLithography). Stl is commonly used in 3D printing.
  • Here is a cube.obj example created using Maya. It uses indexing for efficiency.

• Transformations

  • This week (and in Lab 3) we discuss matrix fundamentals and how matrices are used for the Modeling Transformations.

  • Reading: Transformations are discussed in your text starting on p. 214 (Shreiner)

  • Matrix transformations are used at many stages of the graphics pipeline.

    

    More details can be found here.

  • Matrix Fundamentals

    • What is a matrix?
    • Basic matrix operations: addition, subtraction, multiplication, inverse, transpose, "division", determinants
    • Size matters. Order matters
    • Matrix-vector multiplication. Mv → v'

  • 2D and 3D Matrix Representation of Transformations:

    • scale, rotation, shear, reflection, projection. See 2D Transformation notes and their associated inverses.
    • Rotations and transposes.
    • Translation and Homogeneous coordinates
    • Composition of transformations - Order matters!
    • How to rotation/scale around a point other than the origin.
    • What determinants tell us about reflection, rotation and scale.
    • Euler Rotations and Euler (gimbal lock) Explained. Also see Maya.
    • Quaternion Rotations

  • Scene Graphs: Creating a complex scene or object.
    We will work through the robotic arm in class. If you want to follow along, download this robotic arm starter code.

  • Practice problems

• Deprecated OpenGL Transformation Functions and State Variables:
  The functions below have been deprecated but have been replaced with similarly named matrix functions in the mat.h header and other files (see our code).

  • Matrices
    • Modelview Matrix
    • Projection Matrix

  • Transformation Functions and State Variables:

    Modeling transformation modelview matrix	glTranslate, glRotate, glScale
    Viewing transformation modelview matrix	gluLookAt
    Projection transformation projection matrix	glFrustum, gluPerspective, glOrtho, gluOrtho2
    Viewport transformation	glViewport (still available)

    
    

    

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