# psychopy.tools.gltools.calculateVertexNormals¶

psychopy.tools.gltools.calculateVertexNormals(vertices, faces, shading='smooth')[source]

Calculate vertex normals given vertices and triangle faces.

Finds all faces sharing a vertex index and sets its normal to either the face normal if shading=’flat’ or the average normals of adjacent faces if shading=’smooth’. Flat shading only works correctly if each vertex belongs to exactly one face.

The direction of the normals are determined by the winding order of triangles, assumed counter clock-wise (OpenGL default). Most model editing software exports using this convention. If not, winding orders can be reversed by calling:

faces = np.fliplr(faces)


In some case, creases may appear if vertices are at the same location, but do not share the same index.

Parameters
• vertices (array_like) – Nx3 vertex positions.

• faces (array_like) – Nx3 vertex indices.

• shading (str, optional) – Shading mode. Options are ‘smooth’ and ‘flat’. Flat only works with meshes where no vertex index is shared across faces.

Returns

Vertex normals array with the shame shape as vertices. Computed normals are normalized.

Return type

ndarray

Examples

Recomputing vertex normals for a UV sphere:

# create a sphere and discard normals
vertices, textureCoords, _, faces = gltools.createUVSphere()
normals = gltools.calculateVertexNormals(vertices, faces)