public void Handle(GoToGround message)
{
// TODO: assumes planet is at origin
var planetUnitVector = DoubleVector3.Normalize(_camera.Location);
var height = _planet.GetGroundHeight(_camera.Location);
_camera.Location = planetUnitVector * (height + 2);
}
public double GetGroundHeight(DoubleVector3 observerLocation)
{
// TODO: should probably delegate this responsibility to the terrain object
// TODO: what about water?
var planetUnitVector = DoubleVector3.Normalize(observerLocation - _location);
var height = _generator.GetHeight(planetUnitVector, 19, 8000);
return(_radius + height);
}
bool CalculateIsAboveHorizonToCamera(DoubleVector3 cameraLocation, DoubleVector3 planetLocation, DoubleVector3 closestVertex)
{
// Taken from http://www.crappycoding.com/2009/04/
// TODO: This algorithm is poor. Implement this algorithm instead:
// http://www.gamedev.net/community/forums/mod/journal/journal.asp?jn=263350&reply_id=3173799
// TODO: sometimes the mesh is so large and we're so close the surface that none of the sampled
// vertices are above the horizon. That causes problems when we want to do early termination
// when we do a draw walk on the QuadNode tree (see comments there). Can we add a test here to
// see if we're inside the mesh's bounding box?
var planetToCamera = DoubleVector3.Normalize(cameraLocation - planetLocation);
var planetToMesh = DoubleVector3.Normalize(closestVertex - planetLocation);
var horizonAngle = Math.Acos(_planetRadius * 0.99 / DoubleVector3.Distance(planetLocation, cameraLocation));
var angleToMesh = Math.Acos(DoubleVector3.Dot(planetToCamera, planetToMesh));
return(horizonAngle > angleToMesh);
}
Matrix GetWorldMatrix(DoubleVector3 location, DoubleVector3 cameraLocation)
{
// The mesh stored in the vertex buffer is centered at the origin in order to take it easy on
// the float number system. The camera view matrix is also generated as though the camera were
// at the origin. In order to correctly render the mesh we translate it away from the origin
// by the same vector that the mesh (in double space) is displaced from the camera (in double space).
// We also translate and scale distant meshes to bring them inside the far clipping plane. For
// every mesh that's further than the start of the scaled space, we calcuate a new distance
// using an exponential downscale function to make it fall in the view frustum. We also scale
// it down proportionally so that it appears perspective-wise to be identical to the original
// location. See the Interactive Visualization paper, page 24.
Matrix scaleMatrix;
Matrix translationMatrix;
var locationRelativeToCamera = location - cameraLocation;
var distanceFromCamera = locationRelativeToCamera.Length();
var unscaledViewSpace = _settings.FarClippingPlaneDistance * 0.25;
if (distanceFromCamera > unscaledViewSpace)
{
var scaledViewSpace = _settings.FarClippingPlaneDistance - unscaledViewSpace;
double scaledDistanceFromCamera = unscaledViewSpace + (scaledViewSpace * (1.0 - Math.Exp((scaledViewSpace - distanceFromCamera) / 1000000000)));
var scaledLocationRelativeToCamera = DoubleVector3.Normalize(locationRelativeToCamera) * scaledDistanceFromCamera;
scaleMatrix = Matrix.CreateScale((float)(scaledDistanceFromCamera / distanceFromCamera));
translationMatrix = Matrix.CreateTranslation(scaledLocationRelativeToCamera);
}
else
{
scaleMatrix = Matrix.Identity;
translationMatrix = Matrix.CreateTranslation(locationRelativeToCamera);
}
return(scaleMatrix * translationMatrix);
}
