internal RoadCollection(RoadTopology topology, AssetLoadContext loadContext, HeightMap heightMap)
: this()
{
// The map stores road segments with no connectivity:
// - a segment is from point A to point B
// - with a road type name
// - and start and end curve types (angled, tight curve, broad curve).
// The goal is to create road networks of connected road segments,
// where a network has only a single road type.
// A road network is composed of 2 or more nodes.
// A network is a (potentially) cyclic graph.
// A road node has > 1 and <= 4 edges connected to it.
// A node can be part of multiple networks.
// An edge can only exist in one network.
// TODO: If a node stored in the map has > 4 edges, the extra edges
// are put into a separate network.
var networks = topology.BuildNetworks();
foreach (var network in networks)
{
foreach (var edge in network.Edges)
{
var startPosition = edge.Start.TopologyNode.Position;
var endPosition = edge.End.TopologyNode.Position;
startPosition.Z += heightMap.GetHeight(startPosition.X, startPosition.Y);
endPosition.Z += heightMap.GetHeight(endPosition.X, endPosition.Y);
_roads.Add(AddDisposable(new Road(
loadContext,
heightMap,
edge.TopologyEdge.Template,
startPosition,
endPosition)));
}
}
}
internal Road(
ContentManager contentManager,
HeightMap heightMap,
RoadTemplate template,
Vector3 startPosition,
Vector3 endPosition)
{
const float heightBias = 1f;
const float createNewVerticesHeightDeltaThreshold = 0.002f;
var distance = Vector3.Distance(startPosition, endPosition);
var direction = Vector3.Normalize(endPosition - startPosition);
var centerToEdgeDirection = Vector3.Cross(Vector3.UnitZ, direction);
var up = Vector3.Cross(direction, centerToEdgeDirection);
var halfWidth = template.RoadWidth / 2;
var textureAtlasSplit = 1 / 3f;
var vertices = new List <RoadVertex>();
// Step along road segment in units of 10. If the delta between
// (a) the straight line from previous point to finish and
// (b) the actual height of the terrain at this point
// is > a threshold, create extra vertices.
// TODO: I don't know if this is the right algorithm.
void AddVertexPair(in Vector3 position, float distanceAlongRoad)
{
var u = distanceAlongRoad / 50;
var p0 = position - centerToEdgeDirection * halfWidth;
p0.Z += heightBias;
vertices.Add(new RoadVertex
{
Position = p0,
Normal = up,
UV = new Vector2(u, 0)
});
var p1 = position + centerToEdgeDirection * halfWidth;
p1.Z += heightBias;
vertices.Add(new RoadVertex
{
Position = p1,
Normal = up,
UV = new Vector2(u, textureAtlasSplit)
});
}
AddVertexPair(startPosition, 0);
var previousPoint = startPosition;
var previousPointDistance = 0;
for (var currentDistance = 10; currentDistance < distance; currentDistance += 10)
{
var position = startPosition + direction * currentDistance;
var actualHeight = heightMap.GetHeight(position.X, position.Y);
var interpolatedHeight = MathUtility.Lerp(previousPoint.Z, endPosition.Z, (currentDistance - previousPointDistance) / distance);
if (Math.Abs(actualHeight - interpolatedHeight) > createNewVerticesHeightDeltaThreshold)
{
AddVertexPair(position, currentDistance);
previousPoint = position;
previousPointDistance = currentDistance;
}
}
// Add last chunk.
AddVertexPair(endPosition, distance);
_boundingBox = BoundingBox.CreateFromPoints(vertices.Select(x => x.Position));
_vertexBuffer = AddDisposable(contentManager.GraphicsDevice.CreateStaticBuffer(
vertices.ToArray(),
BufferUsage.VertexBuffer));
var indices = new List <ushort>();
for (var i = 0; i < vertices.Count - 2; i += 2)
{
indices.Add((ushort)(i + 0));
indices.Add((ushort)(i + 1));
indices.Add((ushort)(i + 2));
indices.Add((ushort)(i + 1));
indices.Add((ushort)(i + 2));
indices.Add((ushort)(i + 3));
}
_numIndices = (uint)indices.Count;
_indexBuffer = AddDisposable(contentManager.GraphicsDevice.CreateStaticBuffer(
indices.ToArray(),
BufferUsage.IndexBuffer));
_material = AddDisposable(new RoadMaterial(
contentManager,
contentManager.EffectLibrary.Road));
var texture = contentManager.Load <Texture>(Path.Combine("Art", "Textures", template.Texture));
_material.SetTexture(texture);
}