Vertex normal for triangle strip

[szabolcsdombi]

I was wondering if I could generate vertex normals for triangle strips.
Currently generate_vertex_normals works fine for indexed triangles but I would like to use this feature on triangle strips.

Generating normals for triangle strips may require support for Primitive Restart Index

Here is an example of a surface using triangle strips and primitive restart index.

for i in range(0, 32):
    for j in range(0, 32):
        vertices.append((i / 32, j / 32, height))

for i in range(0, 32 - 1):
    for j in range(0, 32):
        indices.append(i * 32 + j)
        indices.append((i + 1) * 32 + j)
    indices.append(-1)

I could make a PR to implement this feature.

Do we need support for this in Pyrr?

[Korijn]

You could reconstruct a TRIANGLES style index with some vectorized numpy code and reuse the generate_vertex_normals function as-is.

[szabolcsdombi]

Thanks!

Can you please check #66 if the solution is efficient? Is there a better way to do this using numpy?

[Korijn]

• Adding a unit test would definitely help understanding your scenario.
• Is -1 your primitive restart index value?

I think this should work:

zipped = np.array([indices[:-2], indices[1:-1], indices[2:]])
modified_index = zipped[:, ~np.any(zipped == -1, axis=0)].T

[szabolcsdombi]

Thanks!

The primitive restart index will be a parameter. But the default will be -1.

[Korijn]

The numpy version should be faster, particularly for very large indices.