/// <summary>
/// Returns true if two vertices are nearly equal. For example the
/// tangent or normal data does not have to match 100%.
/// Used to optimize vertex buffers and to generate indices.
/// </summary>
/// <param name="a">A</param>
/// <param name="b">B</param>
/// <returns>Bool</returns>
public static bool NearlyEquals(TangentVertex a, TangentVertex b)
{
// Position has to match, else it is just different vertex
return a.pos == b.pos &&
// Ignore blend indices and blend weights, they are the same
// anyway, because they are calculated from the bone distances.
Math.Abs(a.uv.X - b.uv.X) < 0.0001f &&
Math.Abs(a.uv.Y - b.uv.Y) < 0.0001f &&
// Normals and tangents do not have to be very close, we can't see
// any difference between small variations here, but by optimizing
// similar vertices we can improve the overall rendering performance.
(a.normal - b.normal).Length() < 0.1f &&
(a.tangent - b.tangent).Length() < 0.1f;
}
/// <summary>
/// Draw plane vertices
/// </summary>
private void DrawPlaneVertices()
{
// Calculate right and dir vectors for constructing the plane.
// The following code might look strange, but we have to make sure
// that we always get correct up, right and dir vectors. Cross products
// can return (0, 0, 0) if the vectors are parallel!
Vector3 up = plane.Normal;
if (up.Length() == 0)
up = new Vector3(0, 0, 1);
Vector3 helperVec = Vector3.Cross(up, new Vector3(1, 0, 0));
if (helperVec.Length() == 0)
helperVec = new Vector3(0, 1, 0);
Vector3 right = Vector3.Cross(helperVec, up);
Vector3 dir = Vector3.Cross(up, right);
float dist = plane.D;
TangentVertex[] vertices = new TangentVertex[]
{
// Make plane VERY big and tile texture every 10 meters
new TangentVertex(
(-right-dir)*size+up*dist, -size/Tiling, -size/Tiling, up, right),
new TangentVertex(
(-right+dir)*size+up*dist, -size/Tiling, +size/Tiling, up, right),
new TangentVertex(
(right-dir)*size+up*dist, +size/Tiling, -size/Tiling, up, right),
new TangentVertex(
(right+dir)*size+up*dist, +size/Tiling, +size/Tiling, up, right),
};
// Draw the plane (just 2 simple triangles)
BaseGame.Device.DrawUserPrimitives(
PrimitiveType.TriangleStrip, vertices, 0, 2);
}
