/// <summary>
/// Place the (3D) camera such that the 3D terrain is drawn in exactly the same location as the other 2D elements
/// </summary>
/// <param name="drawArea">The area to draw upon (with physical location to pixel transformations)</param>
void UpdateCamera(DrawArea drawArea)
{
// We create a view and projection matrix to allow viewing the world/terrain from the top.
// All Vertices will be in real-world locations relative to a certain reference location
//Using Pi/2 for projection, the distance from camera to plane is the same as the half the distance from top to bottom in the screen.
//
// So if the vertex positions are real world-locations, the camera-target should be at (worldCenterX, 0, worldCenterZ).
// The Cameraposition itself is (world-center-X, cam-height, world-centerZ)
// where camheight is (worldHeight/2 = worldWidth/aspectRatio/2).
// The distance of camera can be very large, so the backplane has to be set accordingly: cam-height/2 and cam-height*2.
WorldLocation upperLeft = drawArea.LocationUpperLeft;
WorldLocation lowerRight = drawArea.LocationLowerRight;
Vector3 groundUpperLeft = locationTranslator.VertexPosition(upperLeft);
Vector3 groundLowerRight = locationTranslator.VertexPosition(lowerRight);
Vector3 cameraTarget = (groundUpperLeft + groundLowerRight) / 2;
float width = groundLowerRight.X - groundUpperLeft.X;
float camHeight = width / device.Viewport.AspectRatio / 2;
Vector3 cameraPosition = cameraTarget;
cameraPosition.Y = -camHeight;
basicEffect.View = Matrix.CreateLookAt(cameraPosition, cameraTarget, new Vector3(0, 0, 1));
basicEffect.Projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver2, device.Viewport.AspectRatio, camHeight / 2, camHeight * 2);
}
/// <summary>
/// Create a single vertex for a corner in the patch
/// </summary>
/// <param name="tile">The tile (parsed .t-file)</param>
/// <param name="patch">The terrain patch (one of the patches in the tile)</param>
/// <param name="cornerIndexX">Defines the x-value of the corner (0 or 1)</param>
/// <param name="cornerIndexZ">Defines the z-value of the corner (0 or 1)</param>
/// <param name="textureName">The name of the texture</param>
private void CreateSingleCornerVertex(Tile tile, terrain_patchset_patch patch, float cornerIndexX, float cornerIndexZ, string textureName)
{
int squaresPerPatch = 16;
cornerIndexX *= squaresPerPatch;
cornerIndexZ *= squaresPerPatch;
var step = tile.SampleSize;
float cornerX = patch.CenterX - 1024;
float cornerZ = patch.CenterZ - 1024 + 2048 * tile.Size;
cornerX += -patch.RadiusM + cornerIndexX * step;
cornerZ += -patch.RadiusM + (squaresPerPatch - cornerIndexZ) * step;
var location = new WorldLocation(tile.TileX, tile.TileZ, cornerX, 0, cornerZ);
// Rotate, Flip, and stretch the texture using the matrix coordinates stored in terrain_patchset_patch
// transform uv by the 2x3 matrix made up of X,Y W,B C,H
var U = cornerIndexX * patch.W + cornerIndexZ * patch.B + patch.X;
var V = cornerIndexX * patch.C + cornerIndexZ * patch.H + patch.Y;
newVertices[textureName].Add(new VertexPositionTexture(locationTranslator.VertexPosition(location), new Vector2(U, V)));
}