d: specifies a factor for dissolve, how much this material dissolves into the background.A value of 1.0 means that light does not bend as it passes through an object. Ni: defines the optical density (aka index of refraction) in the current material.Ns values normally rangeįrom 0 to 1000, with a high value resulting in a tight, concentrated highlight. Ns: defines the focus of specular highlights in the material.Ks: specifies specular color, the color seen where the surface is shiny and mirror-like.In this example, Kd represents a grey color, which will get modified by a colored texture map specified in the map_Kd statement Kd: specifies diffuse color, which typically contributes most of the color to an object.Ka: specifies ambient color, to account for light that is scattered about the entire scene using values between 0 and 1 for the RGB components.The statements that define the characteristics of the material can be in any order. The material definition ends either at the end of the file or at the next newmtl statement. Statements in a material definition consist of a keyword, followed by keyword-specific options, values, or references to supplementary files for use as texture maps. An OBJ file refers to the MTL file in an mtllib declaration and definitions for objects (polygonal or freeform) within the OBJ file can refer to a particular named material definition with a usemtl statement.Īn MTL file contains a sequence of material definitions, each beginning with the keyword newmtl and a name for the material. For example, the definition for a material might specify RGB values for the material's diffuse, ambient, and specular reflectivity, along with other characteristics such as index of refraction and transparency.

The MTL file is a 'library' that can contain one or more named material definitions, each of which can specify color, texture, and reflection characteristics. The ASCII-based MTL file describes surface appearance properties to be applied to polygonal facets or freeform curved patches defined in an OBJ file. Like the OBJ format, the MTL format was used and documented by Wavefront Technologies in the 1990s in association with its Advanced Visualizer software. The Wavefront Material Template Library (MTL) file is a companion file for one or more Wavefront OBJ files. Wavefront Material Template Library (MTL) File Format

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