/// <summary>
/// <para>Compute the normals for each vertex of the mesh, checking the edges cells of other chunks.</para>
/// <para>This process is needed to avoid illumination differences between contiguous cells of different chunks (seams).</para>
/// </summary>
/// <param name="chunk"></param>
protected virtual void ComputeNormals(Chunk chunk)
{
chunk.Normals = new Vector3[(ChunkSize + 1) * (ChunkSize + 1)];
int i, triangleIdx, x, z;
Vector2Int vertexTerrainPos;
Vector3 a, b, c, normal;
// Normal for each vertex
for (i = 0; i < chunk.Vertices.Count; i++)
{
LC_Math.IndexToCoords(i, ChunkSize + 1, out x, out z);
// If isn't edge
if (x < ChunkSize && z < ChunkSize)
{
triangleIdx = LC_Math.CoordsToIndex(x, z, ChunkSize) * 6;
CalculateTrianglesNormals(triangleIdx, chunk);
CalculateTrianglesNormals(triangleIdx + 3, chunk);
}
// If is edge
if (x == 0 || z == 0 || x >= ChunkSize || z >= ChunkSize)
{
vertexTerrainPos = chunk.ChunkPosToTerrain(new Vector2Int(x, z));
a = chunk.Vertices[i];
if (x == 0 || z == 0)
{
b = TerrainPosToReal(vertexTerrainPos.x - 1, chunk.HeightsMap[x, z + 1], vertexTerrainPos.y); // x - 1, z
c = TerrainPosToReal(vertexTerrainPos.x - 1, chunk.HeightsMap[x, z], vertexTerrainPos.y - 1); // x - 1, z - 1
normal = -Vector3.Cross(b - a, c - a);
chunk.Normals[i] += normal;
if (x != 0)
{
chunk.Normals[i - (ChunkSize + 1)] += normal;
}
b = c; // x - 1, z - 1
c = TerrainPosToReal(vertexTerrainPos.x, chunk.HeightsMap[x + 1, z], vertexTerrainPos.y - 1); // x, z - 1
normal = -Vector3.Cross(b - a, c - a);
chunk.Normals[i] += normal;
if (z != 0)
{
chunk.Normals[i - 1] += normal;
}
}
if (x == ChunkSize || z == ChunkSize)
{
b = TerrainPosToReal(vertexTerrainPos.x + 1, chunk.HeightsMap[x + 2, z + 1], vertexTerrainPos.y); // x + 1, z
c = TerrainPosToReal(vertexTerrainPos.x + 1, chunk.HeightsMap[x + 2, z + 2], vertexTerrainPos.y + 1); // x + 1, z + 1
normal = -Vector3.Cross(b - a, c - a);
chunk.Normals[i] += normal;
if (x < ChunkSize)
{
chunk.Normals[i + (ChunkSize + 1)] += normal;
}
b = c; // x + 1, z + 1
c = TerrainPosToReal(vertexTerrainPos.x, chunk.HeightsMap[x + 1, z + 2], vertexTerrainPos.y + 1); // x, z + 1
normal = -Vector3.Cross(b - a, c - a);
chunk.Normals[i] += normal;
if (z < ChunkSize)
{
chunk.Normals[i + 1] += normal;
}
}
}
}
for (i = 0; i < chunk.Normals.Length; i++)
{
chunk.Normals[i].Normalize();
}
}
