Glossary

A

• Aliasing: an effect that reduces the quality of images that are under-sampled.
• Ambient lighting: lighting that is applied equally to all surfaces regardless of normal.
• Antialiasing: a process for reducing aliasing.
• Array buffer: a binding point that is used to specify a buffer that contains vertex attributes.
• Attribute: a type of variable that is used to pass vertex-specific data to vertex shaders.

B

• Binding point: a pointer with a specific purpose.
• Bitmap image: an image stored as an array of fragments.
• Buffer: an array of binary data.

C

• Camera matrix: a matrix that represents the transformation of the camera.
• Clip space: a coordinate system that represents the rendering context in the range $[-1,1]$.
• Clipped: not rasterized due to being outside of clip space.
• Color buffer: a region of a framebuffer that holds color data.
• Color space: a coordinate system that organizes the values of colors in the range $[0,1]$.
• Cubemap: a type of texture that consists of six faces.

D

• Depth buffer: a buffer that stores the depth of fragments.
• Depth testing: the process by which fragments are only rasterized if they pass a test based on the depth buffer.
• Diffuse lighting: directional lighting.
• Directional lighting: lighting that comes uniformly from one direction.
• Dot limit: the cosine of a limit.
• Drawing buffer: the color buffer that contains the fragments that are rasterized to the rendering context.

E

• Element array buffer: a binding point that is used to specify indices on a VAO.
• Environment map: a cubemap that represents the environment of a scene.

F

• Fragment: a pixel.
• Fragment shader: a shader that computes fragment colors.
• Frame: an image in a sequence.
• Framebuffer: a portion of contiguous memory.
• Frame rate: the rate at which frames are rasterized.

G

• GLSL: the OpenGL ES Shading Language; a strictly-typed language that runs on the GPU.
• GLSL ES 3.00: the third version of GLSL; the version of GLSL that WebGL2 shaders use.

H

• Half vector: a vector that sits halfway between two other vectors.

I

• Initialization step: a step that is executed once at the beginning of a program.

L

• Limit: the angle from the direction of a cone to its sides.
• Location: a pointer to a variable in a shader program.

M

• Mip: a smaller version of a texture that is used to rasterize the texture at different sizes.
• Mipmap: a collection of mips.
• Multisampling: a form of antialiasing.

N

• Normal: a unit vector that represents the direction that a surface is facing.
• Normal matrix: the inverse transpose of the rotation portion of a transformation matrix.

O

• OpenGL: the rasterization engine that WebGL is based on.
• OpenGL ES 3.0: the third version of OpenGL; the version of OpenGL that WebGL2 is based on.
• Orthographic projection: a projection that uses parallel lines to project its shape.

P

• Peter panning: an effect resulting from adding a bias to fragment depth that causes shadows to appear slightly disjointed from their caster.
• Perspective projection: a projection that scales its shape based on its distance from the camera.
• Pixel: a discrete unit used to represent visual information.
• Point lighting: lighting that extends in every direction from a point.
• Polygon culling: the process by which only front-facing polygons are rasterized.
• Primitive: points, lines, and triangles; shapes that are understood by computers.
• Projection: a linear transformation from a vector space to itself.
• Projection mapping: the process of projecting an image.
• Projection matrix: a transformation matrix that applies a projection.

R

• Rasterization: the process of drawing one or more primitives with pixels.
• Rasterization engine: an engine that rasterizes primitives.
• Rasterization step: a step that is executed once on each frame.
• Renderbuffer: an object that contains an image.

S

• Sampler: a uniform that is used to sample a texture.
• Scene graph: a general data structure that arranges the local representation of a graphical scene.
• Screen space: a coordinate system that represents the rendering context in the ranges $[0,x]$ and $[0,y]$ for horizontal and vertical coordinates, respectively, where $x$ is the width of the rendering context in pixels and $y$ is the height of the rendering context in pixels.
• Shader: a function that runs on the GPU.
• Shader program: a pair of one vertex shader and one fragment shader that are linked together and used to rasterize primitives.
• Shadow acne: a visual artifact resulting from the limited resolution of a shadow map.
• Shadow map: a texture that contains depth data from the point of view of a light source.
• Skybox: a cubemap that represents the background of a scene.
• Specular lighting: lighting that results from light reflecting off of a shiny surface.
• Spot lighting: lighting that extends in a cone.
• Swizzling: the process of accessing the components of a vector using a specific shorthand syntax.

T

• Texel: a texture element.
• Texture: an array of data that can be randomly accessed.
• Texture complete: the property of a texture that allows it to be rasterized.
• Texture matrix: a modified view projection matrix that also converts from clip space to texture space.
• Texture space: a coordinate system that represents a texture in the range $[0,1]$ from left to right, first pixel to last pixel.
• Texture unit: a value that represents a texture and is passed to a shader program in its stead.
• Tightly-packed: describes data in which the number of bytes from the start of one element to the next is the same as the byte size of the element.
• Transformation matrix: a matrix that represents transformations.

U

• Uniform: a type of variable that is uniform for each vertex.

V

• Varying: a type of variable that varies between each vertex.
• Vertex array object: a collection of information that tells attributes which buffers they should read data from and how they should do it; a VAO.
• Vertex shader: a shader that computes vertex positions.
• View direction matrix: a view matrix with the translation component removed.
• View direction projection matrix: a product of a projection matrix and a view direction matrix.
• View matrix: an inverse of the camera matrix.
• View projection matrix: a product of a projection matrix and a view matrix.
• Viewport: an affine transformation of the horizontal and vertical axes from clip space to screen space.

W

• WebGL: a rasterization engine that is designed to work in the browser.
• WebGL2: the second version of WebGL.
• WebGL API: the interface that allows JavaScript to interact with WebGL.
• World matrix: a transformation matrix that represents the transformation of a node in a scene graph relative to the origin.
• World view projection matrix: a matrix that transforms vertices to appear from the point of view of a camera.