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Unity 3D: A rough and ready computation of normals - useful for procedural meshes

Here is a rough and ready method to compute a meshes' vertex normals knowing the vertices and the indicies of your mesh.



List[] normalBuffer= new List[NumVerts];

for(int vl = 0; vl < normalBuffer.Length; ++vl) {
normalBuffer[vl] = new List();
}

for( int i = 0; i < NumIndices; i += 3 )
{
// get the three vertices that make the faces
Vector3 p1 = m_original[m_mesh.triangles[i+0]];
Vector3 p2 = m_original[m_mesh.triangles[i+1]];
Vector3 p3 = m_original[m_mesh.triangles[i+2]];

Vector3 v1 = p2 - p1;
Vector3 v2 = p3 - p1;
Vector3 normal = Vector3.Cross(v1, v2 );

normal.Normalize();

// Store the face's normal for each of the vertices that make up the face.
normalBuffer[m_mesh.triangles[i+0]].Add(normal);
normalBuffer[m_mesh.triangles[i+1]].Add(normal);
normalBuffer[m_mesh.triangles[i+2]].Add(normal);
}

for( int i = 0; i < NumVerts; ++i )
{
for (int j = 0; j < normalBuffer[i].Count; ++j) {
m_normals[i] += normalBuffer[i][j];
}

m_normals[i] /= normalBuffer[i].Count;
}



Avatar: NeARAZ

Re: Unity 3D: A rough and ready computation of normals - useful for procedural meshes

Hmm... how about mesh.RecalculateNormals()? See here: http://unity3d.com/support/documentation/ScriptReference/Mesh.RecalculateNormals.html
Avatar: montdidier

Re: Unity 3D: A rough and ready computation of normals - useful for procedural meshes

Good Point NeARAZ. I'm glad somebody is paying attention. I wasn't initially aware of this mesh method. I didn't want normals generated automatically via Unity import because I'm currently working with a real time vertex compositor that relies on tagged and known vertex indicies. It appears this mesh method doesn't add vertices and is suitable for my needs.

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