PBR (Physically Based Rendering) Parameters

PBR is an energy-efficient alternative to Proof-of-Work (PoW). Instead of expending vast computational power, participants prove their stake in the network's future by sending coins to a verifiably unspendable address. This eliminates the need for specialized mining hardware (ASICs) and reduces the environmental footprint. The burned coins are permanently removed from circulation, creating inherent scarcity.

The act of burning currency grants the right to mine or validate blocks in proportion to the amount burned. This establishes a cryptoeconomic cost of participation similar to PoW's hardware cost. Consensus is achieved as the network recognizes the burned coins as proof of a sunk cost, aligning the miner's incentives with the long-term health of the blockchain. Larger burns typically translate to a higher probability of mining the next block.

A core technical requirement is a provably unspendable address. This is often an address with a public key for which the corresponding private key is either unknown (e.g., 0x000...dead) or cryptographically impossible to generate. Network nodes can easily verify that coins sent to this address cannot be recovered, making the burn permanent and publicly auditable on the ledger. This transparency is fundamental to the mechanism's security.

PBR can be used to bootstrap a new cryptocurrency by allowing participants to burn a parent chain's coins (e.g., Bitcoin) to receive newly minted coins on the child chain. This method, known as a sidechain or initial coin distribution model, leverages the security and value of an established chain to fairly launch a new one. Slimcoin and Counterparty (XCP) are historical examples that used Bitcoin burns for distribution.

By permanently removing coins from supply, PBR introduces a deflationary pressure on the native token. This reduction in circulating supply, assuming constant or growing demand, can theoretically support the token's value. The mechanism creates a direct economic cost for security, where the value of the burned asset is sacrificed to earn the right to secure the network and collect future rewards.

PBR security relies on the irreversibility of the burn and the economic cost incurred. However, it is susceptible to wealth concentration, where entities with large capital can burn significant amounts to dominate consensus. It may also be less effective than PoW at preventing certain Sybil attacks if the burn event is a one-time cost rather than a continuous expenditure. The security model is fundamentally tied to the market value of the burned asset.

The Base Color (or Albedo) map defines the intrinsic color of a material, free from lighting or shadow. It represents the percentage of light reflected at each wavelength.

• Key Property: Contains no lighting information (shadows, highlights).
• Example: The pure red of unlit clay or the green of untreated copper.
• Data Format: Typically stored as an sRGB texture.

These two parameters are often packed into a single texture. The Metallic channel defines if a surface is a conductor (metal) or dielectric (non-metal). The Roughness channel controls microsurface detail, scattering light to create matte or glossy finishes.

• Metallic Workflow: A value of 1.0 uses the base color as the reflective color.
• Roughness Scale: 0.0 = perfectly smooth (mirror), 1.0 = completely rough (chalk).

A Normal Map simulates high-resolution surface detail (like bumps, grooves, or scratches) without adding geometric complexity. It does this by perturbing the surface normals—the vectors perpendicular to the surface—which changes how light interacts with each pixel.

• Function: Encodes surface direction (X, Y, Z) in RGB channels.
• Result: Creates the illusion of depth and texture on a low-poly mesh.

An Ambient Occlusion map is a grayscale texture that simulates soft shadows in crevices and areas where objects meet. It approximates how accessible a point on a surface is to ambient light, adding contact shadows and depth.

• Pre-computed: Usually baked from a high-poly model.
• Usage: Multiplied with the diffuse lighting to darken occluded areas.

The Emissive parameter defines surfaces that emit their own light, independent of scene lighting. This is used for materials like screens, neon signs, or glowing controls.

• Self-Illumination: Adds light to the scene but does not typically cast light onto other objects (unless paired with global illumination).
• Data: Stored as an RGB color texture and intensity value.

Two dominant workflows package these parameters differently. The Metallic-Roughness workflow (used by glTF, Unity) packs Metallic (B) and Roughness (G) into one texture. The Specular-Glossiness workflow (older) uses separate Specular (RGB) and Glossiness (A) maps.

• Industry Standard: Metallic-Roughness is the modern, more physically accurate standard.
• Conversion: Data can be converted between workflows, but with some approximation.

The Base Color or Albedo map defines the intrinsic color of a material, excluding lighting information. It is a fundamental PBR parameter representing the percentage of light a surface reflects at each wavelength.

• Key Use: Provides the diffuse color under neutral, white lighting.
• Example: A rusted metal surface would have a reddish-brown base color map, while clean copper would be orange-pink.
• Technical Note: Values are typically stored in a non-linear sRGB color space for texture maps.

The Metallic and Roughness parameters are often packed into a single texture. They control the fundamental reflective behavior of a surface.

• Metallic Map: A grayscale map where white (1.0) defines pure metal surfaces (e.g., chrome, gold) and black (0.0) defines non-metals (e.g., plastic, wood). Metals use the base color for specular reflection.
• Roughness Map: A grayscale map controlling surface micro-roughness. Black (0.0) is perfectly smooth (mirror-like), white (1.0) is completely rough (matte, diffuse). This directly affects the size and sharpness of specular highlights.

A Normal Map is a RGB texture that simulates high-resolution surface detail (like bumps, dents, or scratches) without adding geometric complexity. Each pixel's color encodes a surface normal vector direction.

• How it Works: Perturbs the shading normal of a low-polygon mesh to create the illusion of depth.
• Common Use: Adding realistic texture to surfaces like brick, leather, or brushed metal.
• Format: The red, green, and blue channels typically correspond to the X, Y, and Z components of the normal vector in tangent space.

An Ambient Occlusion (AO) map is a grayscale texture that simulates soft shadows in crevices and areas where ambient light is occluded. It is a shading parameter that adds realism and depth.

• Purpose: Darkens cracks, contact points, and folded areas to enhance the perception of shape and contact.
• Application: Multiplied against the diffuse/ambient lighting contribution. It is typically baked from a high-poly model onto a low-poly UV layout.
• Note: AO is a pre-computed approximation and is separate from real-time dynamic shadows.

An alternative to Metallic/Roughness is the Specular/Glossiness workflow. It uses different core maps to achieve similar results.

• Diffuse Map: Similar to Base Color but for non-metals only; metals have a black diffuse value.
• Specular Map: An RGB map defining the color and intensity of specular reflections. For metals, this is the base color.
• Glossiness Map: The inverse of Roughness; white is smooth/shiny, black is rough/matte.
• Context: This workflow is common in older engines and certain industries like archviz.

The foundation of a PBR workflow consists of a few key maps that define a material's fundamental visual properties.

• Albedo/Diffuse: The base color of the material, representing the color of light it reflects, excluding specular highlights. It should be free of lighting information.
• Metallic: A grayscale map that defines whether a surface is metallic (white) or non-metallic (black), controlling how reflections and diffuse color are calculated.
• Roughness: A grayscale map that defines the micro-surface detail, controlling how sharp (black) or blurred (white) reflections and specular highlights appear.

Beyond the core properties, additional maps add fine detail and realism to a material's appearance.

• Normal Map: Simulates surface detail like bumps and grooves by perturbing surface normals, without changing the geometry.
• Ambient Occlusion (AO): A grayscale map that adds soft shadows in crevices and areas where light is occluded, enhancing depth perception.
• Height/Displacement Map: Actually modifies the geometry of a surface, creating true parallax and silhouette changes, which is more computationally expensive than a normal map.

Two primary PBR shading models dominate the industry, each with a slightly different set of core parameters.

• Metallic/Roughness: The most common workflow, used by engines like Unreal Engine and glTF. It uses Albedo, Metallic, and Roughness maps as its core.
• Specular/Glossiness: An alternative workflow, historically used by tools like Unity (Standard shader). It uses Diffuse, Specular (color/intensity of reflections), and Glossiness maps. Most modern pipelines convert to Metallic/Roughness for consistency.

Efficient storage and rendering of PBR textures is critical for performance, especially in real-time applications.

• Channel Packing: Multiple grayscale maps (e.g., Roughness and Ambient Occlusion) are often packed into the Red and Green channels of a single texture file to reduce memory usage and texture samples.
• BCn Formats: Block Compression formats (like BC7 for color, BC5 for normals) are standard on GPUs, drastically reducing texture memory footprint with minimal quality loss.
• Basis Universal: A supercompressed texture format that transcodes to multiple GPU formats at runtime, ideal for web delivery and cross-platform projects.

Creating correct PBR materials requires specialized software and adherence to physical values.

• Substance Suite: Tools like Substance Painter and Substance Designer are industry standards for authoring and exporting PBR material sets with correct, calibrated values.
• Linear Workflow: PBR calculations must be performed in linear color space, not gamma space, to ensure correct light falloff and energy conservation.
• Validators: Tools like the glTF Validator check assets for compliance, ensuring parameters are within physical bounds (e.g., 0-1) and textures are correctly configured.

The base color or diffuse color of a material, representing the proportion of light it reflects without any specular highlights. It is typically a texture map with RGB values between 0 and 1, where pure white (1,1,1) reflects all light and pure black (0,0,0) absorbs all light. Key characteristics:

• Defines the material's inherent color, free from lighting or shadow.
• Should not contain any shading information (e.g., ambient occlusion or specular highlights).
• For metals, the albedo often contains the tint of the metallic reflection.

A parameter (often a grayscale map) that defines whether a surface is a metal (value of 1.0) or a non-metal/dielectric (value of 0.0). This controls how light is reflected and absorbed.

• Metals: Reflect most light specularly; their albedo defines the color of the reflection.
• Non-metals: Reflect a small amount of light specularly (often white/gray) and diffuse the rest according to their albedo.
• Intermediate values can represent corroded or dirty metals.

Controls the microsurface detail of a material, determining how light scatters from its surface. It is typically a grayscale map where 0.0 is perfectly smooth (mirror-like, sharp reflections) and 1.0 is completely rough (matte, blurred or no reflections).

• A key driver for visual realism, affecting specular highlights and reflections.
• Roughness is the inverse of Glossiness (Roughness = 1.0 - Glossiness).
• Examples: Polished marble (low roughness), concrete (high roughness).

A texture that simulates surface detail without modifying the underlying geometry. It uses RGB values to encode the direction (X, Y, Z) of surface normals, creating the illusion of bumps, dents, and grooves.

• Blue (0.5, 0.5, 1.0) represents an unchanged, "flat" surface normal.
• Deviations from blue tilt the normal, affecting how light interacts to create detail.
• A crucial technique for adding high-frequency detail at low performance cost.

A grayscale map that simulates soft shadows in crevices and areas where objects are close together, representing how ambient light is blocked. It adds depth and contact shadows that global illumination might calculate, but as a pre-baked, performance-friendly approximation.

• Darker values indicate areas that receive less ambient light (e.g., cracks, folds).
• Typically multiplied with the diffuse/albedo color in the shading model.
• Often baked from high-poly geometry or sculpted details.

A shading technique that simulates light penetrating a translucent surface, scattering internally, and exiting at a different point. It's essential for realistic rendering of materials like skin, wax, marble, and leaves.

• Often controlled by parameters for Thickness and Scattering Color.
• Approximated in many real-time engines via specialized shaders or pre-integrated maps.
• Creates the characteristic soft, glowing quality of light passing through semi-solid objects.

The Albedo map defines the intrinsic color of a material, representing the diffuse reflection of light. It contains pure color data without any lighting information (shadows or highlights).

• Purpose: Determines the base hue and value of a surface.
• Key Trait: Should be a flat, neutral color under uniform lighting.
• Example: For rusted iron, the albedo would be shades of reddish-brown, not the bright highlights from a light source.

These two parameters are often packed into a single texture. The Metallic map (typically grayscale) defines if a surface is a conductor (1.0, white) or dielectric (0.0, black). The Roughness map controls micro-surface detail, determining if reflections are sharp (0.0, black) or blurry (1.0, white).

• Metallic Workflow: A standard PBR model that uses this map to control both reflectivity and Fresnel behavior.
• Interaction: Roughness affects both metallic and non-metallic surfaces.

A Normal Map is a RGB texture that simulates high-resolution surface detail (like bumps, grooves, or scratches) without adding geometric complexity. Each pixel's color encodes a direction vector, faking the way light interacts with the perturbed surface normals.

• Data Storage: RGB channels correspond to the X, Y, and Z components of the normal vector.
• Visual Impact: Creates the illusion of depth and texture, crucial for realistic materials like stone, fabric, or worn metal.

An Ambient Occlusion map is a grayscale texture that simulates soft shadows in crevices and areas where ambient light is occluded. It adds contact shadows and depth, enhancing the perception of geometric form.

• Baking: Typically baked from a high-poly model onto a low-poly model.
• Usage: Multiplied with the diffuse/albedo color to darken occluded areas, separate from direct lighting calculations.

A PBR Workflow is a standardized, artist-friendly pipeline for creating materials that behave predictably under different lighting conditions. Common workflows include:

• Metallic/Roughness: Uses Albedo, Metallic, Roughness, Normal, and AO maps. Industry standard for real-time engines like Unreal Engine and Unity.
• Specular/Glossiness: An alternative using Albedo, Specular, Glossiness, and Normal maps. More common in some offline renderers.

F0 is the base reflectivity of a material when viewed at a perpendicular (0-degree) angle. It is a fundamental physical property.

• Dielectrics: Non-metals (wood, plastic, stone) have low F0 values (typically 0.02-0.05).
• Conductors: Metals (gold, copper, iron) have high F0 values (0.5-1.0) and are tinted. In the Metallic workflow, F0 is derived from the Albedo and Metallic maps.