Vertex Data in WebGL

• Review of Homework 5
  • Can you give me an overall UML diagram of this system?
  • What is happening in the vertex and fragment shaders?
    • What is the purpose of d in the vertex shader?
    • What is a mat4, vec4?
    • We will move on to discuss how we can form other projection matrices soon.
    • We will also discuss sending over transformation matricies.
  • In the canvas
    • The canvas perhaps should not add the event handler?
  • In the Program
    • How are shapes represented?
      • Does this seem efficient?
  • In the widget
    • Notice responsibility for establishing and displaying a VBO is moved here.
    • bufferData(target, usage)
      • or bufferData(target, size, usage)
      • or bufferData(target, srdData, usage)
      • There are others.
      • target is ARRAY_BUFFER or ELMENT_ARRAY_BUFFER
        • There are other targets.
      • size is the size in bytes
      • srcData is the data that will be copied
        • null will not copy any data but will init buffer
      • Usage
        • gl.STATIC_DRAW : write once read many
        • gl.DYNAMIC_DRAW: write some read many
        • gl.STREAM_DRW: write once read once.
        • There are others.
    • Look at Display
      • bindBuffer
        • gl.ARRAY_BUFFER : attributes
        • gl.ELEMENT_ARRAY_BUFFER: indices
        • There are other buffers available.
      • vertexAttribPointer(index, size, type, normalized, stride, offset)
        • Binds the current buffer to an attribute.
        • Index is the index of a vertex attribute.
          • (The mapping between the attribute and the variable in the shader)
        • Size is the number of components per attribute
          • An integer between 1 and 4 inclusive
        • type is one of the following
          • gl.BYTE - 8 bit
          • gl.SHORT - 16 bit
          • gl.UNSIGNED_BYTE - 8 bit
          • gl.UNSIGNED_SHORT - 16 bit
          • g.FLOAT - 32 bit
        • normalized
          • true if the data should be normalized.
          • Byte and Short [-1, 1]
          • Unsigned [0,1]
          • float: parameter has not effect.
        • stride
          • Offset in bytes between the beginning of consecutive vertex attributes.
          • 0 -> each is next to each other.
          • 4 -> a float between each set
        • offset - size in bytes to the first component.
      • We will spend quite a bit of time looking at this today.
    • For completeness look at drawArrays.
  • Do you understand this program?