CPSC 424 Exam 2 Review Information

Exam 2 will cover material from weeks 3-7 and labs 4-7: the rest of the polygon pipeline (shading and lighting, image textures), generating texture coordinates and procedural textures, and aspects of photorealistic rendering within the polygon pipepline (bump mapping, environment mapping, shadow mapping). three.js and animation will not be on this exam.

The exam will be written (not on the computer), with the focus on concepts rather than specific syntax details — you won't be asked to write actual WebGL code, but you should have a reading knowledge of WebGL and be able to describe or give implementations at the pseudocode level.

• "Reading knowledge" or "reading level" means that you should be familiar enough with WebGL (both the JavaScript and shader parts) to understand and be able to explain or modify code you are given. For specific WebGL operations (such as gl.drawArrays or gl.drawElements) you should be able to plug in the right parameter values for a given situation but you do not need to be able to write the whole call from memory.

• "Pseudocode level" means that you know the steps involved in the code if not necessarily the exact syntax. You can lump together the four statements needed to set up values for shader attributes into a single "set shader parameter X to Y".

You may have a single page of notes (8.5x11", one side) which will be handed in with your exam. This page may be handwritten or typed and can contain whatever you would like, but it must be a hardcopy — on a piece of paper, not a laptop, tablet, phone, or other device — and must be personally prepared by you — you may not copy another student's page or hand out copies of yours to others. Creating your own notes is an essential part of the learning process — deciding what to include requires engagement with the material which reinforces understanding and improves long-term retention of the material, provides an opportunity for review in order to identify gaps in your knowledge in time to ask questions before the exam, increases confidence in what you do know, and encourages taking ownership of your own learning.

Specific topics, terms, and concepts you should be familiar with:

• RGB color and the alpha color component
• terminology: color (represents the fraction of incident light reflected by a surface), spectral distribution, RGB insufficiency
• material properties: ambient color, diffuse color, specular color, shininess (specular exponent)
• kinds of light sources: point, directional, spotlight
• light properties: intensity (ambient, diffuse, specular) + type-specific properties (position, direction, cutoff angle, spot exponent)
• the OpenGL lighting equation — you don't need to be able to produce the standard lighting equation but you should understand the ideas (e.g. the amount of light hitting the surface for diffuse reflection decreases as the angle between the surface normal and the light direction increases) and, seeing the equation, be able to identify what's what
  • its role (specifying how to determine color for a point)
  • generally how light and material contribute to color (light leaving source times fraction reaching surface times fraction reflected towards viewer, at each wavelength)
  • how ambient material color and ambient light contribute to the color
  • how light angle and surface orientation (normal) affect diffuse reflection
  • how light angle, surface orientation (normal), and direction to the viewer affect specular reflection
  • the effect of the shininess material property
  • for spotlights, the effect of the cutoff angle and spot exponent
  • attenuation — what it is, how it affects color
• shading models: flat shading, smooth shading, Phong shading
• face/polygon and vertex normals, how to compute vertex normals for smooth shading
• textures
  • 2D vs 3D textures, image vs procedural textures, cubemap textures: what they are, how they differ (in definition, application, appearance), when to use what
  • texture coordinates: what they are for and how they are used, strategies and techniques for generating 2D texture coordinates when they are not supplied at part of the object's geometry, where texture coordinates come from for 3D textures, what coordinate system is used for texture coordinates and why
  • texture transforms and their effects, including determining the specific transform(s) needed to achieve a particular effect
  • texture repeat modes (clamp to edge, repeat, mirrored repeat) — what each mode does, what they apply to
  • minification and magnification filtering of image textures: what and why, the options and their pros and cons
  • mipmaps — what they are, how they improve minification filtering
  • incorporating textures into lighting (mix, replace, modulate)
• bump mapping
  • what it is / what it is used for
  • the idea/process for bump mapping (steps for computing and what they accomplish, how it fits into lighting)
  • limitations/shortcomings of bump mapping as a strategy
• environment mapping
  • skyboxes: what they are
  • terminology: refraction and index of refraction
  • environment mapping: what it is and what it is used to accomplish, the idea/process of using environment mapping for reflections, limitations/shortcomings of using environment mapping for reflection and refraction
  • dynamic cubemaps: what they are, why they are useful in environment mapping
• shadow mapping
  • what it is / what it is used for
  • the idea/method for shadow mapping
  • limitations/shortcomings of shadow mapping as a strategy
• working with the WebGL programmable pipeline
  • flow of data
  • shaders: what computations are done (viewing pipeline, lighting, texture transforms, application of textures, bump mapping, ...), where (vertex or fragment shader), and why
• materials, textures, lighting and shading in OpenGL 1.1 and their implementation in WebGL
  • what it means for a light position to be in object coordinates, world coordinates, eye coordinates and how to achieve each
  • how the lighting equation is used in OpenGL 1.1 (to determine vertex colors), where it is implemented in WebGL
  • implementing flat, smooth, and Phong shading in OpenGL 1.1 and WebGL
  • implementing shaders: where the lighting equation is computed (for flat, smooth, and Phong shading), where textures are applied
  • texture repeat modes (clamp to edge, repeat, mirrored repeat)
  • minification and magnification filtering of image textures, the options, the issues
  • mipmaps — what they are, how and why they are used for improved minification filtering
• WebGL implementation of photorealistic extensions
  • bump mapping
    • what coordinate system(s) computations are done in and why
    • implementation in WebGL (where the steps for applying bump mapping are written)
  • environment mapping
    • what coordinate system(s) computations are done in and why
    • implementation in WebGL (the steps to render a scene with reflective objects)
  • dynamic cubemaps
    • implementation in WebGL (procedure for generating a dynamic cubemap)
  • framebuffers and renderbuffers
    • what they are
    • their role in generating dynamic cubemaps in WebGL
  • shadow mapping
    • what coordinate system(s) computations are done in and why
    • implementation in WebGL (steps needed, things to be aware of e.g. appropriate size of view volume, shadow map size)
    • artifacts (shadow acne, peter panning, blocky hard-edged shadows) — what they are and why they arise, strategies for reducing/mitigating