Need to experiment with terrain change, and procedural terrain creation, terrain loading/saving.
Code snippet to see how to change trees:
counter += Time.deltaTime;
if (counter>0.1f)
{
counter = 0;
TreeInstance[] trees = terrain.terrainData.treeInstances;
if (trees [ 500 ] .position.y*terrain.terrainData.size.y>50f)
{
trees [ 500 ] .position.y = 5f/ terrain.terrainData.size.y;
}
trees [ 500 ] .position+=Vector3.up * 0.001f;
terrain.terrainData.treeInstances = trees;
terrain.Flush();
Debug.Log("Tree #500 is at "+Vector3.Scale(trees[500].position , terrain.terrainData.size));
}
Working code snippet for lowering terrain. Does not take base terrain position and rotation offset into accunt:
TerrainData td = terrain.terrainData;
int xRes = td.heightmapResolution;
int yRes = td.heightmapResolution;
Vector3 pointHit = hitInfo.point;
testObject.transform.position = hitInfo.point;
int xBase = (int)((hitInfo.point.x / td.size.x) * (float)td.heightmapResolution);
int zBase = (int)((hitInfo.point.z / td.size.z) * (float)td.heightmapResolution);
float[,] heights = terrain.terrainData.GetHeights(xBase, zBase, 1, 1);
//Debug.Log("terrain data xres=" + xRes + ", yres=" + yRes);
Debug.Log(String.Format("Terrain Size={2} Just hit Terrain at coordinates [{0:0.##},{1:0.##}] which is [{3},{4}] Y must be:{5}", hitInfo.point.x, hitInfo.point.z , td.size , xBase , zBase , heights[0,0]*td.size.y));
float[,] newHeights = new float [1,1];
newHeights[0,0] = ((heights[0, 0] * td.size.y) - 0.1f) / td.size.y;
terrain.terrainData.SetHeights(xBase, zBase , newHeights);
Volume of a mesh:
public float SignedVolumeOfTriangle(Vector3 p1, Vector3 p2, Vector3 p3)
{
float v321 = p3.x * p2.y * p1.z;
float v231 = p2.x * p3.y * p1.z;
float v312 = p3.x * p1.y * p2.z;
float v132 = p1.x * p3.y * p2.z;
float v213 = p2.x * p1.y * p3.z;
float v123 = p1.x * p2.y * p3.z;
return (1.0f / 6.0f) * (-v321 + v231 + v312 - v132 - v213 + v123);
}
public float VolumeOfMesh(Mesh mesh)
{
float volume = 0;
Vector3[] vertices = mesh.vertices;
int[] triangles = mesh.triangles;
for (int i = 0; i < mesh.triangles.Length; i += 3)
{
Vector3 p1 = vertices[triangles[i + 0]];
Vector3 p2 = vertices[triangles[i + 1]];
Vector3 p3 = vertices[triangles[i + 2]];
volume += SignedVolumeOfTriangle(p1, p2, p3);
}
return Mathf.Abs(volume);
}
and add this if you need to scale it:
volume *= meshFilter.gameObject.transform.localScale.x * meshFilter.gameObject.transform.localScale.y * meshFilter.gameObject.transform.localScale.z;