Build Quad tangent to vertex point

I’m trying to build some texturized quads tangent to the vertex of a mesh.
I’m not good in transformations and trigonometry but I’m trying hard to handle a bit of the power of this technique.

I get a mess from this shader, the quad stay tangent to the sphere but if I transform then everything mess up.

In attachment the patch and the shader. Please, help me :) (3.7 kB)