private void BuildVisualizationsOfNode(SCNNode node, ref SCNNode verticesNode, ref SCNNode normalsNode)
{
// A material that will prevent the nodes from being lit
var noLightingMaterial = SCNMaterial.Create();
noLightingMaterial.LightingModelName = SCNLightingModel.Constant;
var normalMaterial = SCNMaterial.Create();
normalMaterial.LightingModelName = SCNLightingModel.Constant;
normalMaterial.Diffuse.Contents = NSColor.Red;
// Create nodes to represent the vertex and normals
var positionVisualizationNode = SCNNode.Create();
var normalsVisualizationNode = SCNNode.Create();
// Retrieve the vertices and normals from the model
var positionSource = node.Geometry.GetGeometrySourcesForSemantic(SCNGeometrySourceSemantic.Vertex) [0];
var normalSource = node.Geometry.GetGeometrySourcesForSemantic(SCNGeometrySourceSemantic.Normal) [0];
// Get vertex and normal bytes
var vertexBufferByte = (byte[])positionSource.Data.ToArray();
var vertexBuffer = new float[vertexBufferByte.Length / 4];
Buffer.BlockCopy(vertexBufferByte, 0, vertexBuffer, 0, vertexBufferByte.Length);
var normalBufferByte = (byte[])normalSource.Data.ToArray();
var normalBuffer = new float[normalBufferByte.Length / 4];
Buffer.BlockCopy(normalBufferByte, 0, normalBuffer, 0, normalBufferByte.Length);
// Iterate and create geometries to represent the positions and normals
for (var i = 0; i < positionSource.VectorCount; i++)
{
// One new node per normal/vertex
var vertexNode = SCNNode.Create();
var normalNode = SCNNode.Create();
// Attach one sphere per vertex
var sphere = SCNSphere.Create(0.5f);
sphere.SegmentCount = 4; // use a small segment count for better performances
sphere.FirstMaterial = noLightingMaterial;
vertexNode.Geometry = sphere;
// And one pyramid per normal
var pyramid = SCNPyramid.Create(0.1f, 0.1f, 8);
pyramid.FirstMaterial = normalMaterial;
normalNode.Geometry = pyramid;
// Place the position node
var componentsPerVector = positionSource.ComponentsPerVector;
vertexNode.Position = new SCNVector3(vertexBuffer [i * componentsPerVector], vertexBuffer [i * componentsPerVector + 1], vertexBuffer [i * componentsPerVector + 2]);
// Place the normal node
normalNode.Position = vertexNode.Position;
// Orientate the normal
var up = new Vector3(0, 0, 1);
var normalVec = new Vector3(normalBuffer [i * 3], normalBuffer [i * 3 + 1], normalBuffer [i * 3 + 2]);
var axis = Vector3.Normalize(Vector3.Cross(up, normalVec));
var dotProduct = Vector3.Dot(up, normalVec);
normalNode.Rotation = new SCNVector4(axis.X, axis.Y, axis.Z, NMath.Acos(dotProduct));
// Add the nodes to their parent
positionVisualizationNode.AddChildNode(vertexNode);
normalsVisualizationNode.AddChildNode(normalNode);
}
// We must flush the transaction in order to make sure that the parametric geometries (sphere and pyramid)
// are up-to-date before flattening the nodes
SCNTransaction.Flush();
// Flatten the visualization nodes so that they can be rendered with 1 draw call
verticesNode = positionVisualizationNode.FlattenedClone();
normalsNode = normalsVisualizationNode.FlattenedClone();
}