Computer Graphics Midterm

Flashcards for the Ontario Tech computer graphics course midterm.

What is the graphics pipeline?

Sequence of stages that convert 3D models into a 2D image: modeling, viewing, projection, lighting, rasterization, and fragment processing.

What does the frame buffer do?

Stores the final colour values of all pixels in video memory.

How is colour represented?

Using RGB components
—red, green, and blue combined to form colours.

What is global illumination?

Simulates both direct and indirect light, including reflections and light bouncing.

What is local illumination?

Considers only direct light between sources and surfaces.

What happens in vertex processing?

Transforms 3D coordinates into clip space and computes vertex attributes.

What happens in fragment processing?

Computes final pixel colour using lighting and texture data.

What is the z-buffer?

Stores depth per pixel to decide which surfaces are visible.

What is a vertex shader?

Runs once per vertex to apply transformations and output attributes.

What is a fragment shader?

Runs once per pixel to compute final colour and lighting.

What is an attribute variable?

Per-vertex input like position or normal that changes per vertex.

What is a uniform variable?

Constant value across all vertices or fragments during one draw call.

How are uniforms set?

Via CPU functions like glGetUniformLocation() and glUniform*().

What is a VAO?

Stores vertex attribute configuration and linked buffer objects.

What is a VBO?

Stores raw vertex data such as positions and normals.

What is an index buffer?

Allows reuse of vertices using indices to reduce redundancy.

What is GLFW used for?

Window creation and input handling in OpenGL.

What is GLEW used for?

Manages and loads OpenGL extensions.

What is GLM used for?

Provides vectors, matrices, and transformations for OpenGL.

What is a polygon mesh?

Collection of vertices, edges, and faces forming 3D surfaces.

What is a normal vector?

Perpendicular vector to a surface, used in lighting calculations.

What are the three standard transformations?

Translation, rotation, and scaling.

Why use homogeneous coordinates?

Enable translation and projection via 4×4 matrix multiplication.

How to rotate about a specific point?

Translate to origin, rotate, then translate back.

What is hierarchical modeling?

Organizes objects into parent-child structures for linked transformations.

What is a master and an instance?

Master defines geometry; instance applies transformations to reuse it.

What is parametric representation?

Defines points as functions of parameters (u, v).

What is implicit representation?

Defines a surface as all points satisfying f(x, y, z) = 0.

What are Cn and Gn continuity?

Cn ensures derivative continuity; Gn ensures direction continuity only.

What is a Bezier curve?

Curve defined by control points using blending functions within convex hull.

What is the viewing transformation?

Converts world coordinates to camera coordinates.

What is orthographic projection?

Parallel projection that preserves size and shape.

What is perspective projection?

Simulates depth
—objects appear smaller when farther away.

What is the canonical view volume?

Normalized cube (-1 \le x, y, z \le 1) after projection.

What is back-face culling?

Removes polygons facing away from the camera to improve speed.

What is z-fighting?

Flickering from similar depth values; fix by increasing precision or offset.

What are BSP trees?

Divide space for efficient visibility sorting using polygon planes.

What is the Phong lighting model?

Combines ambient, diffuse, and specular reflection components.

What is ambient reflection?

Constant base light that illuminates surfaces uniformly.

What is diffuse reflection?

Light scattered equally
—intensity \propto cos(angle) between light and normal.

What is specular reflection?

Mirror-like highlight depending on view direction and shininess.

What is Lambert’s cosine law?

Diffuse reflection intensity is proportional to cos(angle) between light and normal.

What is a half-vector?

Vector halfway between light and view directions for specular computation.

What are directional, point, and spot lights?

Directional: parallel rays; Point: radiates in all directions; Spot: cone light.

What is Flat shading?

One colour per polygon using a single normal.

What is Gouraud shading?

Lighting at vertices with interpolated colours across polygons.

What is Phong shading?

Interpolates normals per pixel for smooth lighting.

What is material colour?

Defines how surfaces reflect ambient, diffuse, and specular light.

What is the purpose of the LookAt transformation?

Positions and orients the camera relative to the scene.

Why does transformation order matter?

Matrix multiplication is not commutative
—order changes result.

What is clipping?

Removes geometry outside the viewing volume before rasterization.

What is the difference between vertex and fragment shaders?

Vertex shader transforms geometry; fragment shader colours pixels.

What does the frame buffer store?

Final rendered image pixels and their colours.