Reading 3D Files in OBJ Format

The core challenge of reading OBJ format 3D files in MATLAB lies in parsing text data and converting it into operable point sets. OBJ files represent a common 3D model storage format, typically containing vertex coordinates, texture coordinates, normal vectors, and other geometric information, where vertex data forms the foundation of 3D models.

Implementing OBJ file reading in MATLAB requires line-by-line text parsing. The process begins by loading the OBJ file using file reading functions like fopen and textscan. Subsequently, the algorithm iterates through each line of data, identifying lines starting with "v" which represent vertex coordinates. After extraction, vertex data can be stored as an N×3 matrix where each row corresponds to a point's X, Y, Z coordinates using array manipulation functions like sscanf for numeric conversion.

Beyond vertex data, OBJ files may contain additional information such as face connectivity (lines starting with "f"), though these elements can be ignored when only point cloud data is required. This approach enables the conversion of 3D models into MATLAB point sets, facilitating subsequent visualization using plot3 or scatter3, analysis, or processing operations.

For beginners, mastering this method helps understand fundamental 3D model structures and MATLAB's text processing capabilities through practical file I/O operations and string manipulation techniques.