public void ConstructMesh(out Vector3[] vertices, out int[] triangles, out Vector3[] vertexNormals)
{
vertices = new Vector3[resolution * resolution];
vertexNormals = new Vector3[resolution * resolution];
triangles = new int[(resolution - 1) * (resolution - 1) * 6];
int triIndex = 0;
int i = 0;
for (int y = 0; y < resolution; ++y)
{
for (int x = 0; x < resolution; ++x)
{
Vector2 percent = new Vector2(x, y) / (resolution - 1);
// fit point on plane (the plane is always same size but different number of points)
Vector3 pointOnUnitCube = localUp + (percent.x - .5f) * 2 * axisA + (percent.y - .5f) * 2 * axisB;
Vector3 pointOnUnitSphere = pointOnUnitCube.Normalized();
vertices[i] = shapeGenerator.CalculatePopintOnPlanet(pointOnUnitSphere);
// calculate the vertex that will draw the triangle, clockwise
if (x != resolution - 1 && y != resolution - 1)
{
triangles[triIndex] = i;
triangles[triIndex + 1] = i + resolution + 1;
triangles[triIndex + 2] = i + resolution;
triangles[triIndex + 3] = i;
triangles[triIndex + 4] = i + 1;
triangles[triIndex + 5] = i + resolution + 1;
triIndex += 6;
}
i++;
}
}
// Normals calculation
// Zero-out our normal buffer to start from a clean slate.
for (int v = 0; v < vertices.Length; v++)
{
vertexNormals[v] = Vector3.Zero;
}
// For each face, compute the face normal, and accumulate it into each vertex
for (int index = 0; index < triangles.Length; index += 3)
{
int vertexA = triangles[index];
int vertexB = triangles[index + 1];
int vertexC = triangles[index + 2];
var edgeAB = vertices[vertexB] - vertices[vertexA];
var edgeAC = vertices[vertexC] - vertices[vertexA];
// The cross product is perpendicular to both input vectors (normal to the plane).
// Flip the argument order if you need the opposite winding.
//var areaWeightedNormal = edgeAB.Cross(edgeAC);
var areaWeightedNormal = edgeAC.Cross(edgeAB);
vertexNormals[vertexA] += areaWeightedNormal;
vertexNormals[vertexB] += areaWeightedNormal;
vertexNormals[vertexC] += areaWeightedNormal;
}
// Finally, normalize all the sums to get a unit-length, area-weighted average.
for (int v = 0; v < vertices.Length; v++)
{
vertexNormals[v] = vertexNormals[v].Normalized();
}
}