Appendix D: Glossary

ACES — Academy Color Encoding System. A standardized color space and tone mapping curve used for filmic HDR rendering.

AABB — Axis-Aligned Bounding Box. A rectangular box whose edges are aligned with the coordinate axes, used for fast collision and culling tests.

BRDF — Bidirectional Reflectance Distribution Function. Describes how light reflects from a surface at a given point, as a function of incoming and outgoing directions.

Bloom — A post-processing effect that simulates lens glare by blurring bright regions of an image and adding them back.

Cascade Shadow Map (CSM) — A technique for directional light shadows that splits the view frustum into multiple depth ranges, each with its own shadow map resolution.

Clip Space — The coordinate space after the projection matrix transform. In WebGPU, clip-space depth is [0, 1].

Compute Shader — A GPU shader stage that performs general-purpose computation, not tied to rendering geometry.

Cook-Torrance — A microfacet BRDF model using the GGX normal distribution, Smith geometry function, and Schlick Fresnel approximation.

DDA — Digital Differential Analyzer. An algorithm for traversing a voxel grid along a ray, used for block ray casting.

Deferred Shading — A rendering technique where surface properties are written to a G-Buffer in a first pass and lighting is computed in a separate pass.

Depth of Field (DoF) — A post-processing effect simulating camera lens defocus, where objects at a specific distance are sharp and others are blurred.

Forward Rendering — A rendering technique where lighting is computed per-vertex or per-fragment during the geometry pass, as opposed to deferred.

Fragment Shader — The GPU shader stage that computes the color of each rasterized pixel fragment.

Fresnel — The phenomenon where the reflectance of a surface increases at glancing angles. The Schlick approximation is commonly used in PBR.

Frustum Culling — The process of determining whether an object's bounding volume intersects the camera's view frustum, skipping objects outside the view.

G-Buffer — Geometry Buffer. A set of textures storing surface properties (albedo, normal, depth, roughness, metallic) for deferred shading.

GGX — A normal distribution function (NDF) used in the Cook-Torrance BRDF, characterized by its specular highlight shape with long tails.

God Rays — Volumetric light shafts, also known as crepuscular rays, caused by light scattering through partially occluded volumes.

HDR — High Dynamic Range. A rendering pipeline that uses floating-point textures to represent a wider range of brightness values than standard 8-bit sRGB.

IBL — Image-Based Lighting. A technique that uses an HDR environment map to illuminate surfaces with distant light.

LOD — Level of Detail. Simplified versions of geometry used at greater distances to reduce rendering cost.

Material — A combination of shader code, textures, and parameters that defines the appearance of a surface.

NDC — Normalized Device Coordinates. The coordinate space after the perspective divide (x∈[-1,1], y∈[-1,1], z∈[0,1] for WebGPU).

PBR — Physically Based Rendering. A shading approach that models light transport using physically accurate BRDFs and energy-conserving equations.

PCF — Percentage-Closer Filtering. A shadow filtering technique that samples the shadow map multiple times with a comparison sampler and averages the results.

Pipeline — An immutable GPU state object combining shaders, vertex layout, blend state, depth state, and primitive configuration.

Render Pass — A phase of GPU work between beginRenderPass() and end(), targeting a set of color and depth attachments.

Render Graph — A dependency graph of passes, rebuilt every frame from persistent pass instances. Passes declare read/write resource usage via a typed builder; the graph compiler validates, culls, topologically sorts, and binds physical resources from a pooled cache, then executes the survivors into a single command buffer. See src/renderer/render_graph/.

SSAO — Screen-Space Ambient Occlusion. A technique that estimates ambient occlusion by sampling the depth buffer around each pixel.

SSGI — Screen-Space Global Illumination. A technique that estimates indirect light bounces using the G-Buffer and previous frame color.

TAA — Temporal Anti-Aliasing. A technique that reduces aliasing by jittering the sample position each frame and blending with previous frames.

Tone Mapping — The process of converting HDR color values to the display's dynamic range (usually SDR).

TRS — Translation-Rotation-Scale. The decomposition of a local transform into its three component transforms.

Vertex Shader — The GPU shader stage that transforms vertices from model space to clip space.

VSM — Variance Shadow Maps. A shadow technique that stores depth and depth-squared to enable pre-filtered soft shadows.

WebGPU — A modern web graphics API providing explicit, low-overhead access to GPU functionality, compatible with D3D12, Metal, and Vulkan.

WGSL — WebGPU Shading Language. The shader language for WebGPU, designed for safe, portable GPU programming on the web.