vertex indicubng opgengl code example
Example: HOW TO CALCULATE INDEX BUFFER FROM VERTICIES
CalculateVertexNormals(Vector3[] vertexPositions, int[] triangleIndices, Vector3[] vertexNormals)
{
// Zero-out our normal buffer to start from a clean slate.
for(int vertex = 0; vertex < vertexPositions.Length; vertex++)
vertexNormals[vertex] = Vector3.zero;
// For each face, compute the face normal, and accumulate it into each vertex.
for(int index = 0; index < triangleIndices.Length; index += 3) {
int vertexA = triangleIndices[index];
int vertexB = triangleIndices[index + 1];
int vertexC = triangleIndices[index + 2];
var edgeAB = vertexPositions[vertexB] - vertexPositions[vertexA];
var edgeAC = vertexPositions[vertexC] - vertexPositions[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 = Vector3.Cross(edgeAB, edgeAC);
// Don't normalize this vector just yet. Its magnitude is proportional to the
// area of the triangle (times 2), so this helps ensure tiny/skinny triangles
// don't have an outsized impact on the final normal per vertex.
// Accumulate this cross product into each vertex normal slot.
vertexNormals[vertexA] += areaWeightedNormal;
vertexNormals[vertexB] += areaWeightedNormal;
vertexNormals[vertexC] += areaWeightedNormal;
}
// Finally, normalize all the sums to get a unit-length, area-weighted average.
for(int vertex = 0; vertex < vertexPositions.Length; vertex++)
vertexNormals[vertex] = Vector3.Normalize(normal);
}