| getTangents {rgl2gltf} | R Documentation |
Use the MikkTSpace code to generate tangent vectors.
Description
This function generates tangent vectors using the MikkTSpace code by Morten S. Mikkelsen.
Usage
getTangents(obj)
Arguments
obj |
A triangles or quads object as returned by |
Details
glTF files include normal textures, which require the tangent space to be specified: the normals at each vertex are supplemented with a tangent vector and a bitangent vector that is their cross product. The standard recommends that if the glTF file doesn't specify tangents, they should be generated using the MikkTSpace code.
Note that a comment in ‘mikktspace.h’ indicates that indexing needs to be recalculated after computing the tangents, so this function works on unindexed inputs, and reapplies indexing at the end.
Value
A modified copy of the original object, adding a 4 column
tangents entry. The order and number of indices
may have changed.
Author(s)
Morten S. Mikkelsen, Johannes Kuehnel and Duncan Murdoch.
References
The MikkTSpace code was obtained from https://github.com/mmikk/MikkTSpace. The interface code is based on code from https://www.turais.de/using-mikktspace-in-your-project/ by Johannes Kuehnel.