Tangent vectors.

Coding Python Support
1

Hello !

So I have a mesh and I need to do a script that computes the tangent vectors of each vertices.
How can I proceed without an UV map ?

Sorry for my bad english.

2

You can’t without UV-Map:

RuntimeError: Error: Tangent space computation needs an UVMap, “(null)” not found, aborting

But it should suffice to create a blank UV map…

import bpy

ob = bpy.context.object
me = ob.data

uv_tex = me.uv_textures.new()
uv_layer = me.uv_layers[-1]

me.calc_tangents(uv_layer.name)

print()
print("%-6s  %-6s  %-30s  %-30s" % ("Loop", "Vertex", "Tangent", "Bitangent"))
print("-" * 80)

r = lambda x: round(x, 4)

for l in me.loops:
    print("%6i  %6i  %-30s  %-30s" % (l.index, l.vertex_index, tuple(map(r, l.tangent)), tuple(map(r, l.bitangent))))
3

Thank you!

4

And a silly question but where can I find the source code of this function to see how it is done ?

5

It’s somewhere in blender\source\blender\blenkernel\intern, parts of it in mesh_evaluate.c

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