/// <summary>
/// Verifies that the tree at the given index is sufficiently spaced
/// from the other trees. If trees are placed too closely, one tree
/// can quickly pop in front of the other as the camera angle
/// changes.</summary>
/// <param name="treeIndex">index of tree we are testing</param>
/// <returns>true if valid, false otherwise</returns>
bool IsTreePositionValid(Vector3Fixed pos)
{
if (trees.Count < 1)
{
return(true);
}
float x = (float)pos.X;
float z = (float)pos.Z;
for (int i = 0; i < trees.Count; i++)
{
double fDeltaX =
Math.Abs(x - (float)((Tree)trees[i]).Position.X);
double fDeltaZ =
Math.Abs(z - (float)((Tree)trees[i]).Position.Z);
if (3.0 > Math.Pow(fDeltaX, 2) + Math.Pow(fDeltaZ, 2))
{
return(false);
}
}
return(true);
}
/// <summary>
/// Render the trees in the sample
/// </summary>
protected void DrawTrees()
{
Vector3Fixed eyePartFixed;
eyePartFixed = new Vector3Fixed();
eyePartFixed.X = (FixedPoint)eyePart.X;
eyePartFixed.Y = (FixedPoint)eyePart.Y;
eyePartFixed.Z = (FixedPoint)eyePart.Z;
// Set diffuse blending for alpha set in vertices.
renderState.AlphaBlendEnable = true;
renderState.SourceBlend = Blend.SourceAlpha;
renderState.DestinationBlend = Blend.InvSourceAlpha;
// Enable alpha testing (skips pixels with less than a
// certain alpha.)
if (device.DeviceCaps.AlphaCompareCaps.SupportsGreaterEqual)
{
device.RenderState.AlphaTestEnable = true;
device.RenderState.ReferenceAlpha = 0x08;
device.RenderState.AlphaFunction = Compare.GreaterEqual;
}
// Loop through and render all trees
device.SetStreamSource(0, treeVertexBuffer, 0);
foreach (Tree t in trees)
{
// Quick culling for trees behind the camera
// This calculates the tree position relative to the
// camera, and projects that vector against the camera's
// direction vector. A negative dot product indicates a
// non-visible tree.
if (0 > (t.Position.X - eyePartFixed.X) *
GlobalDirection.X + (t.Position.Z - eyePartFixed.Z) *
GlobalDirection.Z)
{
break;
}
// Set the tree texture
device.SetTexture(0, treeTextures[t.TreeTextureIndex]);
// Translate the billboard into place
billboardMatrix.M41 = t.Position.X;
billboardMatrix.M42 = t.Position.Y;
billboardMatrix.M43 = t.Position.Z;
device.Transform.WorldFixed = billboardMatrix;
// Render the billboard
device.DrawPrimitives(PrimitiveType.TriangleStrip,
t.OffsetIndex, 2);
}
// Restore state
device.Transform.World = Matrix.Identity;
device.RenderState.AlphaTestEnable = false;
device.RenderState.AlphaBlendEnable = false;
}
