public static bool TestRayPolygon(LVector2 o, LVector2 dir, LVector2 *points, int vertexCount,
ref LVector2 point)
{
LFloat t = LFloat.FLT_MAX;
for (var i = 0; i < vertexCount; i++)
{
var b1 = points[i];
var b2 = points[(i + 1) % vertexCount];
var inter = TestRaySegment(o, dir, b1, b2);
if (inter >= 0)
{
if (inter < t)
{
t = inter;
}
}
}
if (t < LFloat.FLT_MAX)
{
point = o + dir * t;
}
return(false);
}
/// <summary>
/// 射线和多边形
/// </summary>
/// <param name="o"></param>
/// <param name="dir"></param>
/// <param name="points"></param>
/// <param name="vertexCount"></param>
/// <returns></returns>
public static bool TestRayPolygon(LVector2 o, LVector2 dir, LVector2 *points, int vertexCount)
{
for (int i = 0; i < vertexCount; i++)
{
LVector2 b1 = points[i];
LVector2 b2 = points[(i + 1) % vertexCount];
int inter = TestRaySegment(o, dir, b1, b2);
if (inter >= 0)
{
return(true);
}
}
return(false);
}
//http://www.kevlindev.com/geometry/2D/intersections/index.htm
//http://www.kevlindev.com/geometry/2D/intersections/index.htm
//https://bitlush.com/blog/circle-vs-polygon-collision-detection-in-c-sharp
public static bool TestCirclePolygon(LVector2 c, LFloat r, LVector2 *_points, int vertexCount)
{
var radiusSquared = r * r;
var circleCenter = c;
var nearestDistance = LFloat.MaxValue;
int nearestVertex = -1;
for (var i = 0; i < vertexCount; i++)
{
LVector2 axis = circleCenter - _points[i];
var distance = axis.sqrMagnitude - radiusSquared;
if (distance <= 0)
{
return(true);
}
if (distance < nearestDistance)
{
nearestVertex = i;
nearestDistance = distance;
}
}
LVector2 GetPoint(int index)
{
if (index < 0)
{
index += vertexCount;
}
else if (index >= vertexCount)
{
index -= vertexCount;
}
return(_points[index]);
}
var vertex = GetPoint(nearestVertex - 1);
for (var i = 0; i < 2; i++)
{
var nextVertex = GetPoint(nearestVertex + i);
var edge = nextVertex - vertex;
var edgeLengthSquared = edge.sqrMagnitude;
if (edgeLengthSquared != 0)
{
LVector2 axis = circleCenter - vertex;
var dot = LVector2.Dot(edge, axis);
if (dot >= 0 && dot <= edgeLengthSquared)
{
LVector2 projection = vertex + (dot / edgeLengthSquared) * edge;
axis = projection - circleCenter;
if (axis.sqrMagnitude <= radiusSquared)
{
return(true);
}
else
{
if (edge.x > 0)
{
if (axis.y > 0)
{
return(false);
}
}
else if (edge.x < 0)
{
if (axis.y < 0)
{
return(false);
}
}
else if (edge.y > 0)
{
if (axis.x < 0)
{
return(false);
}
}
else
{
if (axis.x > 0)
{
return(false);
}
}
}
}
}
vertex = nextVertex;
}
return(true);
}
//TODO
public static bool TestPolygonPolygon(LVector2 *_points, int vertexCount, LVector2 *_points2, int vertexCount2)
{
return(false);
}
/// <summary>
/// 测试圆和多边形是否相交
/// </summary>
/// <param name="c"></param>
/// <param name="r"></param>
/// <param name="_points"></param>
/// <param name="vertextCount">多边形顶点数量</param>
/// <returns></returns>
public static bool TestCirclePolygon(LVector2 c, LFloat r, LVector2 *_points, int vertextCount)
{
//圆形的半径平方
var radiusSquared = r * r;
//圆的中心点
var circleCenter = c;
// 记录最近的距离
var nearestDistance = LFloat.MaxValue;
// 记录最近的顶点
int nearestVertex = -1;
for (int i = 0; i < vertextCount; i++)
{
LVector2 axix = circleCenter - _points[i];
// 多边形的任何顶点在圆的范围内 说明相交
var distance = axix.sqrMagnitude - radiusSquared;
if (distance <= 0)
{
return(true);
}
if (distance < nearestDistance)
{
nearestVertex = i;
nearestDistance = distance;
}
}
// 获取点
LVector2 GetPoint(int index)
{
if (index < 0)
{
index += vertextCount;
}
else if (index >= vertextCount)
{
index -= vertextCount;
}
return(_points[index]);
}
var vertex = GetPoint(nearestVertex - 1);
for (int i = 0; i < 2; i++)
{
LVector2 nextVertex = GetPoint(nearestVertex + 1);
LVector2 edge = nextVertex - vertex;
LFloat edgeLengthSquared = edge.sqrMagnitude;
if (edgeLengthSquared != 0)
{
LVector2 axis = circleCenter - vertex;
LFloat dot = LVector2.Dot(edge, axis);
if (dot >= 0 && dot <= edgeLengthSquared)
{
// (dot / edgeLengthSquare ) * edge 是求 向量的投影
// 两向量 a' b' 夹角β
// a·b = |a'||b'|cosβ
//
LVector2 projection = vertex + (dot / edgeLengthSquared) * edge;
axis = projection - circleCenter;
if (axis.sqrMagnitude <= radiusSquared)
{
return(true);
}
else
{
if (edge.x > 0)
{
if (axis.y > 0)
{
return(false);
}
else if (edge.x < 0)
{
if (axis.y < 0)
{
return(false);
}
else if (edge.y > 0)
{
if (axis.x < 0)
{
return(false);
}
else
if (axis.x > 0)
{
return(false);
}
}
}
}
}
}
}
vertex = nextVertex;
}
return(true);
}
