public const float Epsilon = 1E-5f; //for numerical imprecision
/// <summary>
/// Checks whether a ray intersects a triangle
/// </summary>
/// <returns>closest intersection point</returns>
public static float? RayIntersectTriangle(Ray ray, Vector3[] vertices,
Matrix transform, out Triangle triangle)
{
triangle.v1 = triangle.v2 = triangle.v3 = Vector3.Zero;
// Keep track of the closest triangle we found so far,
// so we can always return the closest one.
float? closestIntersection = null;
Vector3 v1 = Vector3.Zero;
Vector3 v2 = Vector3.Zero;
Vector3 v3 = Vector3.Zero;
// Loop over the vertex data, 3 at a time (3 vertices = 1 triangle).
for (int i = 0; i < vertices.Length; i += 3)
{
// Perform a ray to triangle intersection test.
float? intersection;
// Transform the three vertex positions into world space
v1 = Vector3.Transform(vertices[i], transform);
v2 = Vector3.Transform(vertices[i + 1], transform);
v3 = Vector3.Transform(vertices[i + 2], transform);
RayIntersectsTriangle(ray, v1, v2, v3, out intersection);
// Does the ray intersect this triangle?
if (intersection != null)
{
// If so, is it closer than any other previous triangle?
if ((closestIntersection == null) ||
(intersection < closestIntersection))
{
// Store the distance to this triangle.
closestIntersection = intersection;
// Store the three vertex positions into the vertex parameters.
triangle.v1 = v1;
triangle.v2 = v2;
triangle.v3 = v3;
}
}
}
return closestIntersection;
}
/// <summary>
/// It checks for the collision between a collision ray and a collision model.
/// </summary>
protected bool TestRayintersectModel(Ray ray, Vector3[] vertices,
Matrix transform,
out Vector3 intersect,
out Vector3 normal,
out float distance)
{
Triangle outTriangle = new Triangle(Vector3.Zero, Vector3.Zero,
Vector3.Zero);
distance = 0.0f;
intersect = Vector3.Zero;
normal = Vector3.Zero;
totalCollidingCount += vertices.Length;
// Test ray with the model
float? checkDistance = Helper3D.RayIntersectTriangle(ray, vertices,
transform, out outTriangle);
if (checkDistance != null)
{
// Retry test for intersect point and normal
return Helper3D.PointIntersect(ray.Position, ray.Direction, outTriangle,
out distance, out intersect, out normal);
}
return false;
}
/// <summary>
/// ray intersect face and return intersection distance, point and normal.
/// </summary>
public static bool PointIntersect(Vector3 rayOrigin, Vector3 rayDirection,
Triangle triangle, out float intersectDistance,
out Vector3 intersectPosition, out Vector3 intersectNormal)
{
intersectDistance = 0.0f;
intersectPosition = rayOrigin;
intersectNormal = Vector3.Zero;
Vector3 uvt = Vector3.Zero;
if (RayTriangleIntersect(rayOrigin, rayDirection,
triangle.v1, triangle.v2, triangle.v3,
out uvt.Z, out uvt.X, out uvt.Y))
{
intersectDistance = uvt.Z;
intersectPosition = (1.0f - uvt.X - uvt.Y) * triangle.v1 + uvt.X *
triangle.v2 + uvt.Y * triangle.v3;
intersectNormal = Vector3.Normalize(
Vector3.Cross(triangle.v3 - triangle.v1, triangle.v2 - triangle.v1));
return true;
}
return false;
}
/// <summary>
/// Checks whether a ray intersects a model. This method needs to access
/// the model vertex data,
/// Returns the distance along the ray to the point of intersection, or null
/// if there is no intersection.
/// </summary>
/// <returns>closest intersection point</returns>
public static float? RayIntersectModel(Ray ray, Model model,
Matrix worldTransform, out bool insideBoundingSphere, out Triangle triangle)
{
triangle.v1 = triangle.v2 = triangle.v3 = Vector3.Zero;
// Look up our custom collision data from the Tag property of the model.
Dictionary<string, object> tagData = (Dictionary<string, object>)model.Tag;
if (tagData == null)
{
throw new InvalidOperationException(
"Model.Tag is not set correctly. Make sure your model " +
"was built using the custom CollideProcessor.");
}
// Start off with a fast bounding sphere test.
BoundingSphere boundingSphere = (BoundingSphere)tagData["BoundingSphere"];
if (boundingSphere.Intersects(ray) == null)
{
// If the ray does not intersect the bounding sphere, we cannot
// possibly have picked this model, so there is no need to even
// bother looking at the individual triangle data.
insideBoundingSphere = false;
return null;
}
else
{
// The bounding sphere test passed, so we need to do a full
// triangle picking test.
insideBoundingSphere = true;
// Keep track of the closest triangle we found so far,
// so we can always return the closest one.
float? closestIntersection = null;
// Loop over the vertex data, 3 at a time (3 vertices = 1 triangle).
Vector3[] vertices = (Vector3[])tagData["Vertices"];
for (int i = 0; i < vertices.Length; i += 3)
{
// Perform a ray to triangle intersection test.
float? intersection;
RayIntersectsTriangle(ray,
vertices[i],
vertices[i + 1],
vertices[i + 2],
out intersection);
// Does the ray intersect this triangle?
if (intersection != null)
{
// If so, is it closer than any other previous triangle?
if ((closestIntersection == null) ||
(intersection < closestIntersection))
{
// Store the distance to this triangle.
closestIntersection = intersection;
// Transform the three vertex positions into world space,
// and store them into the output vertex parameters.
triangle.v1
= Vector3.Transform(vertices[i], worldTransform);
triangle.v2
= Vector3.Transform(vertices[i + 1], worldTransform);
triangle.v3
= Vector3.Transform(vertices[i + 2], worldTransform);
}
}
}
return closestIntersection;
}
}
