Difference between revisions of "Texture types"

Latest revision as of 13:49, 24 May 2015

These are some of the map types used when texturing game models. In all cases, the different map types work together to produce the final image rendered onscreen. Artists create these maps in tandem to ensure the contribution from each work in balance. In most cases, these images can be considered masks for material attributes that work on a per-pixel level, instead of a single-value slider, such as transparency or gloss.

The most common types are diffuse, emissive, normal, opacity, specular, and gloss. Which types you use will be dictated by the asset itself, and the Art Direction for the project. Depending on the needs of a game, multiple types may be packed into a single file.

In a Physically-based rendering scheme, the common types are albedo, microsurface, reflectivity, and normal maps.

• Brief Considerations About Materials by Pedro Toldeo is an explanation of various map types, especially specular maps.
• Texturing for Dummies by Leigh van der Byl is a PDF overview of texturing and texture types. (alternative download site)

Color Maps

The most common type is diffuse, the colors seen on the model. This map varies in appearance the most, due to art direction or technical requirements of a given asset.

• Diffuse maps are used to create the albedo, the diffuse reflection of light from a surface.
• Albedo maps are a more specialized form of diffuse used in PBR shaders, and represent only the base colors of a surface.
• Detail maps are tiled detail textures that are blended in when geometry is viewed up close.
• Gradient maps and Color look-up tables can be used to modify colors of a scene or model by mapping one color to another in a 1d or 2d fashion. These are typically global assets, not specific to any model.
• Masking for color variation, player customizable assets, or material regions can be considered color maps.

Transparency Maps

• Transparency maps, also known as opacity, are used to cut out parts of a surface, usually for alpha blending. For example: fire, grass, hair, smoke, water, windows, etc.

Bump Maps

• Bump maps are 2d grayscale maps that modify shading of geometry, typically used for fine detail of a surface.
• Normal maps are 3D bump maps that modify Vertex normals to give the appearance of higher detailed geometry.
• Radiosity normal maps are a specialized blending of light maps and normal maps.
• Displacement maps are similar to bump but store height information and modify geometry when rendered, modifying both appearance of shading and silhouette.
• Height maps are typically used to deform terrain meshes moving vertices up and down.
• Vector displacement maps are an extension of height, but can transform vertices in any axis.
• Wrinkle maps vary in implementation, but store localized bump values for wrinkles on clothing when characters bend in certain ways.

- The following aren't necessarily bump types, but work to a similar effect.

• Parallax maps "slide" other textures along a surface simulating height and depth in geometry.
• DuDv maps modify UVs of a mesh to distort the other textures on a per-pixel basis.
• Flow maps are similar to DuDv, defining direction-based distortion, such as water flow or anisotropic highlighting.
• Curvature maps are notable for use during production, storing convexity/concavity in greyscale.

Specular Maps

• Specular maps control how reflective the surface is, and can adjust the shape of the reflection. Specular usually simulates only the reflections of the brightest light sources in a scene. Specular maps can also be used to control how much environment maps will appear on a surface.
• Gloss maps control how wide or narrow the specular highlight appears.
• Roughness maps are Gloss maps in a PBR system, representing how smooth or rough a surface is. Also called Microsurface.
• Reflectivity is Specular in a PBR system, representing how much light is reflected off a surface.
• Metallic maps are an alternate to Reflectivity in PBR, they differ by marking materials as metallic or non-metallic. In this method, the Albedo map works like regular with non-metals, but it acts as reflectivity for metal areas. Also called Metalness.
• Anisotropic maps govern the shape of the specular highlights from real-time lights, often used for hair shading.
• Brdf maps govern reflection by mapping camera angles to light values.
• Fresnel / Rim light maps are used to control how much light appears on extreme angles of a surface, such as velvet or small fine hair.

Environment Maps

Environment maps are typically used for reflective surfaces, showing the scene around the model, what is being reflected. This is a cheap hack to avoid rendering an accurate view of the actual scene, which is typically too slow to render in real time.

• Cube maps are the most common type, which features six faces of a panorama mapped to a cube.
• Diffusely convolved cube map is a blurred cube map that better represents the ambient light than an accurate reflection.
• Spherical environment map AKA Litsphere or MatCap is a simple, single-image reflection, mapping light and color values to angles of a hemisphere.

Light Maps

• Light maps store complex pre-computed lighting for surfaces in a scene.
• Ambient occlusion maps are pre-computed calculations of ambient light bounce on a surface.
• Cavity maps are narrower version of ambient occlusion, keeping dark shadows to crevices and sharp corners only.
• Emissive map (aka Glow or Self-illumination) mimic surfaces that emit light, like a computer monitor, a vehicle dashboard at night, or magical effects.
• Radiosity normal maps are a specialized blending of light maps and normal maps.
• Thickness maps are a measurement of how thick/thin a surface is. Typically used for faking light passing through a surface when lit from behind, such as a cat's ear or a stretched hide.

Other Maps

• Texture Coordinates AKA UV maps refer to the unwrapped shape of a model, used in production as a wireframe template when working in a 2d image editor during texturing.
• SSS / Subsurface Scattering maps fake the behavior of light bounce inside of a semitranslucent surface, such as skin or wax.
• Subdermal maps are used in skin shaders, representing the layer underneath skin: fatty tissue, blood tone and blood vessels.