private void CollectVisiblePages(TerrainVegetationRenderData renderData, TerrainVegetationComponent component, CameraComponent camera)
{
renderData.TransformData.Clear();
if (camera == null || renderData.Pages == null)
{
return;
}
var cameraPosition = camera.GetWorldPosition();
cameraPosition.Y = 0.0f; // Only cull in xz plane
var maxPageDistance = component.ViewDistance + PageSize;
_activesPages.Clear();
for (var i = 0; i < renderData.Pages.Length; i++)
{
var page = renderData.Pages[i];
if (page.Instances == null) // Skip uninitialized pages
{
continue;
}
var distance = (cameraPosition - page.WorldPosition).Length();
if (distance < maxPageDistance)
{
_activesPages.Add(page);
}
}
// Reset camera position for individual instance culling
cameraPosition = camera.GetWorldPosition();
float maxDistance = component.ViewDistance;
float minDistance = maxDistance * 0.8f;
float distanceRange = maxDistance - minDistance;
// TODO: concurrency??? That would probably be a good thing here
var maxInstanceDistanceSquared = component.ViewDistance * component.ViewDistance;
foreach (var page in _activesPages)
{
for (var p = 0; p < page.Instances.Count; p++)
{
var distance = (cameraPosition - page.Instances[p].TranslationVector).LengthSquared();
//if (distance < maxInstanceDistanceSquared)
{
var worldMatrix = page.Instances[p];
if (component.UseDistanceScaling)
{
// Fade out the mesh by scaling it, this could be done in the shader for more speeeed
var distanceToCamera = Math.Max(0.0f, (cameraPosition - worldMatrix.TranslationVector).Length() - minDistance);
var relativeScale = Math.Min(1.0f, distanceToCamera / distanceRange);
var distanceScale = (float)MathUtil.Lerp(1.0f, 0.0f, Math.Pow(relativeScale, 2.0f));
var scale = Matrix.Scaling(distanceScale);
renderData.TransformData.Add(scale * worldMatrix);
}
else
{
renderData.TransformData.Add(worldMatrix);
}
}
}
}
}
