public static Vector3 ClosestPointOnSurface(TerrainCollider collider, Vector3 to, float radius, bool debug = false)
{
var terrainData = collider.terrainData;
var local = collider.transform.InverseTransformPoint(to);
// Calculate the size of each tile on the terrain horizontally and vertically
float pixelSizeX = terrainData.size.x / (terrainData.heightmapResolution - 1);
float pixelSizeZ = terrainData.size.z / (terrainData.heightmapResolution - 1);
var percentZ = Mathf.Clamp01(local.z / terrainData.size.z);
var percentX = Mathf.Clamp01(local.x / terrainData.size.x);
float positionX = percentX * (terrainData.heightmapResolution - 1);
float positionZ = percentZ * (terrainData.heightmapResolution - 1);
// Calculate our position, in tiles, on the terrain
int pixelX = Mathf.FloorToInt(positionX);
int pixelZ = Mathf.FloorToInt(positionZ);
// Calculate the distance from our point to the edge of the tile we are in
float distanceX = (positionX - pixelX) * pixelSizeX;
float distanceZ = (positionZ - pixelZ) * pixelSizeZ;
// Find out how many tiles we are overlapping on the X plane
float radiusExtentsLeftX = radius - distanceX;
float radiusExtentsRightX = radius - (pixelSizeX - distanceX);
int overlappedTilesXLeft = radiusExtentsLeftX > 0 ? Mathf.FloorToInt(radiusExtentsLeftX / pixelSizeX) + 1 : 0;
int overlappedTilesXRight = radiusExtentsRightX > 0 ? Mathf.FloorToInt(radiusExtentsRightX / pixelSizeX) + 1 : 0;
// Find out how many tiles we are overlapping on the Z plane
float radiusExtentsLeftZ = radius - distanceZ;
float radiusExtentsRightZ = radius - (pixelSizeZ - distanceZ);
int overlappedTilesZLeft = radiusExtentsLeftZ > 0 ? Mathf.FloorToInt(radiusExtentsLeftZ / pixelSizeZ) + 1 : 0;
int overlappedTilesZRight = radiusExtentsRightZ > 0 ? Mathf.FloorToInt(radiusExtentsRightZ / pixelSizeZ) + 1 : 0;
// Retrieve the heights of the pixels we are testing against
int startPositionX = pixelX - overlappedTilesXLeft;
int startPositionZ = pixelZ - overlappedTilesZLeft;
int numberOfXPixels = overlappedTilesXRight + overlappedTilesXLeft + 1;
int numberOfZPixels = overlappedTilesZRight + overlappedTilesZLeft + 1;
// Account for if we are off the terrain
if (startPositionX < 0)
{
numberOfXPixels -= Mathf.Abs(startPositionX);
startPositionX = 0;
}
if (startPositionZ < 0)
{
numberOfZPixels -= Mathf.Abs(startPositionZ);
startPositionZ = 0;
}
if (startPositionX + numberOfXPixels + 1 > terrainData.heightmapResolution)
{
numberOfXPixels = terrainData.heightmapResolution - startPositionX - 1;
}
if (startPositionZ + numberOfZPixels + 1 > terrainData.heightmapResolution)
{
numberOfZPixels = terrainData.heightmapResolution - startPositionZ - 1;
}
// Retrieve the heights of the tile we are in and all overlapped tiles
var heights = terrainData.GetHeights(startPositionX, startPositionZ, numberOfXPixels + 1, numberOfZPixels + 1);
// Pre-scale the heights data to be world-scale instead of 0...1
for (int i = 0; i < numberOfXPixels + 1; i++)
{
for (int j = 0; j < numberOfZPixels + 1; j++)
{
heights[j, i] *= terrainData.size.y;
}
}
// Find the shortest distance to any triangle in the set gathered
float shortestDistance = float.MaxValue;
Vector3 shortestPoint = Vector3.zero;
for (int x = 0; x < numberOfXPixels; x++)
{
for (int z = 0; z < numberOfZPixels; z++)
{
// Build the set of points that creates the two triangles that form this tile
Vector3 a = new Vector3((startPositionX + x) * pixelSizeX, heights[z, x], (startPositionZ + z) * pixelSizeZ);
Vector3 b = new Vector3((startPositionX + x + 1) * pixelSizeX, heights[z, x + 1], (startPositionZ + z) * pixelSizeZ);
Vector3 c = new Vector3((startPositionX + x) * pixelSizeX, heights[z + 1, x], (startPositionZ + z + 1) * pixelSizeZ);
Vector3 d = new Vector3((startPositionX + x + 1) * pixelSizeX, heights[z + 1, x + 1], (startPositionZ + z + 1) * pixelSizeZ);
Vector3 nearest;
BSPTree.ClosestPointOnTriangleToPoint(ref a, ref d, ref c, ref local, out nearest);
float distance = (local - nearest).sqrMagnitude;
if (distance <= shortestDistance)
{
shortestDistance = distance;
shortestPoint = nearest;
}
BSPTree.ClosestPointOnTriangleToPoint(ref a, ref b, ref d, ref local, out nearest);
distance = (local - nearest).sqrMagnitude;
if (distance <= shortestDistance)
{
shortestDistance = distance;
shortestPoint = nearest;
}
if (debug)
{
DebugDraw.DrawTriangle(a, d, c, Color.cyan);
DebugDraw.DrawTriangle(a, b, d, Color.red);
}
}
}
return(collider.transform.TransformPoint(shortestPoint));
}
