CPSC 424, Fall 2021: Information About the Second Test

The second and last test will be given in class on Monday, November 15. It will cover Chapter 4 (OpenGL 1.1 light and material), Chapter 5 (three.js), and the first four sections of Chapter 6 (WebGL, not including 3D graphics). Any questions about textures will be about textures in WebGL, not OpenGL. As for Blender, the only thing that you might be asked about is keyframe animation.

The format of the test will be the usual: some essay questions and definitions; reading some code and explaining its purpose; writing some code. There will not be a lot of code writing. You do not need to memorize every function and method that we have encountered, but you should should be able to write code using those that are listed below, except those that are listed as requiring only a "reading knowledge" (which means that you might be given some code and asked to explain what it does).

Here are some terms and ideas that you should be familiar with:

Light and material in OpenGL 1.0
material properties: 
     ambient color, 
     diffuse color, 
     specular color, 
     shinininess (also called specular exponent)
color represents the fraction of incident light that is reflected by a surface
light properties:
     diffuse intensity,
     specular intensity
directional light from direction (x,y,z), position = (x,y,z,0)
point light at (x,y,z), position = (x,y,z,1)
operations on vectors:  dot product, length, normalize
unit vector (length = 1)
the dot product of two unit vectors gives the cosine of the angle between the vectors
normal vectors to a surface
setting normal vectors:  glNormal3f(x,y,z)
    [ might also need:  gl.Begin(primitive), gl.End(), gl.Vertex3f(x,y,z) ]
normal vectors for flat shading versus normal vectors for smooth shading
the lighting equation: how visible color of a point on a surface is computed
     how ambient material color and ambient light contribute to the color
     how light angle and normal vector affect diffuse reflection
     how light angle, normal, and direction to viewer affect specular reflection               
     the effect of the "shininess" material property

a READING knowledge of the OpenGL API for light and material:
    glEnable(gl_LIGHTING), glEnable(GL_LIGHT0), glEnable(GL_LIGHT1), ...
    glMaterialfv( side, property, value )
         value is an array of 4 numbers (or a pointer)
    glMateriali( side, property, value )
         property is GL_SHININESS, value is 0 to 128
    glLightfv( light, property, value )
         light is GL_LIGHT0, GL_LIGHT1, ...
         property is gl_POSITION, gl_DIFFUSE, gl_SPECULAR, gl_AMBIENT
         value is an array of 4 numbers (or a pointer)

Three.js:  A 3D scene graph API for WebGL
basic requirements for rendering an image:  scene, camera, renderer
the basic rendering command:   renderer.render( scene, camera )
the class THREE.Object3D represents scene graph nodes, with properties
      obj.add(object) -- adds an object as a child of obj
      obj.clone() -- make a copy, including copying transformations
      obj.position (for translation)-- obj.position.x,obj.position.y,obj.position.z
      obj.scale (for scaling)-- obj.scale.x, obj.scale.y, obj.scale.z
      obj.rotation (for rotations)-- obj.rotation.x, obj.rotation.y, obj.rotation.z
applying transformations using obj.position, obj.rotation, obj.scale
building hierarchical structures with Three.js
geometry and material (required for a visible object)
creating a mesh object with  new Three.Mesh( geometry, material )
how THREE.BufferGeometry() relates to WebGL VBOs
Lambert material vs. Phong material
basic constructors from the three.js API:
    new THREE.Mesh( geometry, material )
    new THREE.SphereGeometry( radius, slices, stacks )  -- center at (0,0,0)
    new THREE.CylinderGeometry( topRadius, bottomRadius, height, slices )
           -- center at (0,0,0), axis along the y-axis
    new MeshLambertMaterial({ color: c })
    new MeshPhongMaterial({ color: c, specular: s })
a READING knowledge of other things from the three.js API:
    new THREE.Scene()  -- the root node of the scene graph
    new THREE.WebGLRenderer()  -- used for rendering a scene
    new THREE.BufferGeometry() -- for creating geometry directly
    new THREE.BufferAttribute( float32Array, numsPerVertex )
    bufferGeometry.setAttribute("postion", bufferAttribute)
    bufferGeometry.setAttribute("normal", bufferAttribute)
    new THREE.PerspectiveCamera(fovy,aspect,near,far)

WebGL 1.0
OpenGL 1.1 uses a fixed-function pipeline
WebGL uses a programmable pipeline
why does modern OpenGL use a programmable pipeline?
shader programs
vertex shader
fragment shader
the flow of data in the WebGL programmable pipeline
uniform variable
attribute variable
varying variable
uniform and attribute variable values come from JavaScript
a varying variable must be declared in both the vertex shader and the fragment shader
values for varying variables in fragment shader are interpolated from vertices
JavaScript API for uniform variables:
    gl.getUniformLocation(prog, uniformName)
    gl.uniform1i(uniformLocation, n)
    gl.uniform1f(uniformLocation, x)
    gl.uniform2f(uniformLocation, x, y)
    gl.uniform3f(uniformLocation, x, y, z)
Typed arrays:  Float32Array, Uint16Array, Uint8Array
a READING knowledge of the JavaScript API for attribute variables:
    gl.bindBuffer(gl.ARRAY_BUFFER, buffer)
    gl.bufferData(buffer, typedArray, gl.STATIC_DRAW)  // or gl.STREAM_DRAW
    gl.getAttribLocation(prog, attributeName)
    gl.vertexAttribPointer(attributeLocation, numsPerVertex, type, false, 0, 0)
    gl.drawArrays( primitive, startVertex, vertexCount )
primitives include gl.POINTS, gl.LINES, gl.TRIANGLES
the difference between gl.STREAM_DRAW and gl.STATIC_DRAW
buffers are Vertex Buffer Objects (VBO)
why VBOs are used for attribute values
the importance of limiting data exchange between CPU and GPU
GLSL 1.00 shader programming language
basic GLSL:
   the entry point to a shader:   void main() { ... }
   basic types:   bool, int, float, vec2, vec3, vec4
   constructors such as  vec4( color, 1.0 ) or vec3(1,1,1)
   referring to vector components as v.x, v.y, v.z, v.w or as v.r, v.g, v.b, b.a
   declaring and using uniform, attribute, and varying variables
   vertex shader assigns a value to gl_Position (of type vec4)
      (gl_POSITION gives the coordinates in "clip", or "normalized device," coords)
   fragment shader assigns a value to gl_FragColor (of type vec4)
   gl_PointSize and gl_PointCoords for primitives of type gl.POINTS
   control strictures:  if statement and basic for loop
   the sampler2D type
   texture lookup with the function  texture2D( sampler, texCoords );
texture objects
texture units
how texture units relate to sampler2D variables in the shader
setting the value of a sampler variable using gl.uniform1i()
image textures
the asynchronous loading problem for images in JavaScript
texture coordinates, and how they are used on a primitive
texture coordinates in shader programs (using an attribute and a varying variable)
texture repeat modes: how are texcoords outside the range 0 to 1 are treated
minification and magnification filtering of image textures
how and why mipmaps are used for improved minification filtering

a READING knowledge of the basic WebGL texture API:
   gl.activeTexture(gl.TEXTURE0), gl.activeTexture(gl.TEXTURE1), ...
   gl.bindTexture(gl.TEXTURE_2D, textureObject)
   gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image)