/// <summary>
/// Gets the point of the terrain that the mouse cursor is currently casting a ray to.
/// Returns null if the ray range is surpassed.
/// </summary>
/// <param name="projectionMatrix">
/// The projection matrix.
/// </param>
/// <param name="viewMatrix">
/// The view matrix.
/// </param>
/// <param name="terrain">
/// The terrain.
/// </param>
/// <returns>
/// The <see cref="Vector3?"/>
/// </returns>
public static Vector3 GetTerrainPoint(
GraphicsDevice device,
Matrix projectionMatrix,
Matrix viewMatrix,
ITerrain terrain)
{
Ray ray = CastRay(device, projectionMatrix, viewMatrix);
Vector3 currentTerrainPoint = BinarySplitSearch(0, Range, ray, terrain, BinarySplits);
if (!IsIntersectionInRange(0, Range, ray, terrain))
{
currentTerrainPoint.Y = terrain.GetWorldHeight(currentTerrainPoint.X, currentTerrainPoint.Z);
}
return(currentTerrainPoint);
}
/// <summary>
/// Affects entities with gravity
/// </summary>
/// <param name="gameTime">
/// The game time.
/// </param>
/// <param name="terrain">
/// The terrain.
/// </param>
public void GravityAffect(GameTime gameTime, ITerrain terrain)
{
float height = terrain.GetWorldHeight(this.Position.X, this.Position.Z);
if (this.Position.Y < height)
{
this.Position = new Vector3(this.Position.X, height, this.Position.Z);
}
else if (this.Position.Y > height || this.Weight < 0)
{
float y =
this.Position.Y -
(this.Weight *
(float)gameTime.ElapsedGameTime.TotalSeconds);
y = y < height ? height : y;
this.Position = new Vector3(this.Position.X, y, this.Position.Z);
}
}
/// <summary>
/// Custom split binary search implementation.
/// Returns the closest point projected from the mouse cursor
/// to the terrain surface.
/// </summary>
/// <param name="start">
/// The start.
/// </param>
/// <param name="finish">
/// The finish.
/// </param>
/// <param name="ray">
/// The ray.
/// </param>
/// <param name="terrain">
/// The terrain.
/// </param>
/// <param name="binarySplits">
/// The number of splits for the binary search.
/// </param>
/// <returns>
/// The <see cref="Vector3"/>.
/// </returns>
private static Vector3 BinarySplitSearch(
float start,
float finish,
Ray ray,
ITerrain terrain,
uint binarySplits = 1)
{
binarySplits = binarySplits == 0 ? 1 : binarySplits;
Vector3[] endpoints = new Vector3[binarySplits];
// The section size of each split
float sectionSize = binarySplits > 0 ? (finish - start) / binarySplits : finish - start;
bool found = false;
int iterations = 0;
for (uint i = 0; i < binarySplits; i++)
{
iterations++;
float s = i * sectionSize;
float f = (i + 1) * sectionSize;
bool intersectionFound = false;
Vector3 endpoint = BinarySearch(s, f, ray, terrain, out intersectionFound);
if (intersectionFound)
{
found = true;
float height = terrain.GetWorldHeight(endpoint.X, endpoint.Z);
Vector3 vertice = new Vector3(endpoint.X, height, endpoint.Z);
float distance = Vector3.Distance(endpoint, vertice);
// If the point found is in the seamless range
// skip the rest of the search and return it
if (distance <= SeamlessDistance)
{
return(endpoint);
}
}
endpoints[i] = endpoint;
}
// If no point was in intersection range with terrain during search
// returns furthest point in range
if (!found)
{
Vector3 furthestEndpoint = BinarySearch(start, finish, ray, terrain, out found);
return(furthestEndpoint);
}
// Calculates the best result from all splits
// Only reachable if no seamless result is found during split search
Vector3 winner = endpoints[0];
foreach (var endpoint in endpoints)
{
float winnerHeight = terrain.GetWorldHeight(winner.X, winner.Z);
Vector3 winnerVertice = new Vector3(winner.X, winnerHeight, winner.Z);
float winnerDistance = Vector3.Distance(winner, winnerVertice);
float height = terrain.GetWorldHeight(endpoint.X, endpoint.Z);
Vector3 currentVertice = new Vector3(endpoint.X, height, endpoint.Z);
float currentDistance = Vector3.Distance(endpoint, currentVertice);
if (currentDistance < winnerDistance)
{
winner = endpoint;
}
}
return(winner);
}
/// <summary>
/// Checks if the specified point is under the terrain
/// </summary>
/// <param name="testPoint">
/// The test point.
/// </param>
/// <param name="terrain">
/// The terrain.
/// </param>
/// <returns>
/// The <see cref="bool"/>.
/// </returns>
private static bool IsUnderGround(Vector3 testPoint, ITerrain terrain)
{
float height = terrain.GetWorldHeight(testPoint.X, testPoint.Z);
return(testPoint.Y < height);
}
/// <summary>
/// Snaps the entity Y position to the terrain Y at the specified point
/// </summary>
/// <param name="terrain">
/// The terrain.
/// </param>
public void SnapToTerrainHeight(ITerrain terrain)
{
float height = terrain.GetWorldHeight(this.Position.X, this.Position.Z);
this.Position = new Vector3(this.Position.X, height, this.Position.Z);
}
