Computer Graphics Midterm

Raster Images

pictures made up of a grid of tiny colored squares called pixels

High Dynamic Range (HDR)

Includes colors that aren’t defined by sRGB such as color of sunlight (10 bits so it can store more values for one color while LDR does 8 bit). HDR provides a wider range of brightness and contrast than standard LDR

Interleaved Storage

More common because we need RGB values together rather than separate [RGB, RGB, RGB]

Separate Channels

RRR GGG BBB

BMP (Bitmap Image File)

Uncompressed image format

PPM (Portable Pixmap Image File)

Uncompressed

PNG (Portable Network Graphics)

Lossless compression

JPEG (Joint Photographic Experts Group)

Lossy compression

EXR (OpenEXR by ILM)

HDR format with lossy or lossless compression. Common in visual effects and film production

Swizzled Order

Data accessed in Z-shaped pattern

Gamma

relationship between a pixel’s numerical value (like its RGB value) and the actual brightness (luminance) that appears on a display. (usually around 2.2)

Gamma and Human Perception

Humans distinguish darker tones more easily than brighter ones. This is why gamma correction is used in displays

Alpha Blending

Combines foreground and background using alpha (transparency) values

World Space

The global coordinate system where the entire 3D scene exists. All objects, lights, and cameras are positioned relative to a shared origin (0,0,0). Used to describe how objects relate to each other in the same “world.”

Object (Material) Space

The local coordinate system of an individual object. Coordinates are defined relative to the object’s own origin (often at its center).

Affine Transformations

Transformations where lines remain straight and parallel lines stay parallel

Rotation (Affine/Linear)

Rotates an object about its center

Scale (Affine/Linear)

Changes an object’s size

Homogeneous Coordinates

a way to represent points in 2D or 3D space using an extra coordinate.

Viewing Volume

The cube or 3D area that we see from the 2D view

Z-Axis Orientation

The z-axis points toward the camera (opposite the direction you face)

World Space Transformation

Objects are transformed from object to world space using model transformations

Camera (View) Space

a coordinate system used in computer graphics to represent objects relative to the camera

GPU Pipeline

Hardware-accelerated rendering process: Scene data → Transformations → Rasterization → Coloring → Final graphic

GPU

Generates high-quality images on the screen

Geometric Shader

Runs once per primitive (triangle, line, point) and can create more primitives, fewer primitives, or modify them.

Vertex Shader

3D programmable stage that processes one vertex at a time .Transforms vertices from object space → world space → camera space → clip space. and passes data downstream

Fragment Shader

2D programmable stage that outputs color for each fragment

Rasterization

Converts primitives into pixels

Primitive Clipping

Removes primitives outside canonical space

Viewport in Gasket Program

Defines where image is shown on canvas (needed even with canvas)

Flatten Function

Sends data to GPU efficiently, data is formed as a single continuous line for easy memory access

gl.drawArrays

Executes vertex shader for each vertex

gl.POINTS

Renders points

gl.LINES

Draws lines between vertex pairs (0–1)

gl.LINE_STRIP

Connects all vertices except last to first

gl.LINE_LOOP

Connects all vertices and closes the loop

Immediate Mode Graphics

Displays each point immediately

Retained Mode Graphics

Stores geometry for reuse (requires CPU→GPU transfer)

Hidden Surface Removal

Determines which surfaces are visible to viewer

Z-Buffer Algorithm

Stores depth info per pixel to resolve visibility .Clear z-buffer before redraws

Single Buffering

One buffer, less memory but more flickering

Double Buffering

Two buffers swapped for smooth display, uses twice as much memory

De Casteljau’s Algorithm

Subdivides control points to generate smooth Bezier curves

B-Spline Curves

Smooth curves satisfying partition of unity

NURBS

Non-uniform rational B-splines, can space control points, assign different weights to each point, defines curves. (line doesn’t necessarily go through control points just influenced by it)

Interpolating Curves

Pass through all control points

Catmull-Clark Subdivision

Algorithm for smoothing 3D meshes by subdividing polygons

Barycentric Coordinates

a way to express the position of a point relative to the vertices of a triangle.

P=αv0​+βv1​+γv2​

gl.TRIANGLES

Forms one triangle per three vertices

gl.TRIANGLE_STRIP

Connected triangles sharing previous two vertices

gl.TRIANGLE_FAN

Triangles sharing one central vertex

Texture Sampling

Determines color by sampling nearby pixels

Nearest-Neighbor Sampling

Picks closest pixel (blocky look)

Bilinear Filtering

Blends four nearby pixels for smoothness

Mipmaps

Pre-scaled texture levels for efficient rendering of distant objects. Reduces aliasing and improves performance

Orthographic view

2D representation of a 3D object, created by looking at it from a single, straight-on direction, such as from the front, top, or side

Perspective view

a way to represent a three-dimensional (3D) scene on a two-dimensional (2D) surface, creating an illusion of depth and distance as they appear to the eye

Linear transformations

must map the origin to the origin,