void GetCrossPoint()
{
if (crossPoints == null)
{
crossPoints = new List <FrustrumPoint>();
}
crossPoints.Clear();
Matrix_VP = cam.projectionMatrix * cam.worldToCameraMatrix;
Matrix_I_VP = Matrix_VP.inverse;
for (int i = 0; i < 12; i++)
{
FrustrumPoint crossPoint = new FrustrumPoint();
if (IsSegmentIntersectOcean(segments[i, 0], segments[i, 1], OceanLevel, ref crossPoint))
{
crossPoints.Add(crossPoint);
}
}
//为了留出裕度，统统向外扩张5%
Vector4 middle = Vector4.zero;
foreach (var p in crossPoints)
{
middle += p.worldPos;
}
middle /= crossPoints.Count;
for (int i = 0; i < crossPoints.Count; i++)
{
crossPoints[i].worldPos = (crossPoints[i].worldPos - middle) * (1 + outScale) + middle;
}
}
void Resort4Point(ref List <FrustrumPoint> list)
{
Vector3 s1 = (Vector3)(crossPoints[1].worldPos - crossPoints[0].worldPos);
Vector3 s2 = (Vector3)(crossPoints[2].worldPos - crossPoints[1].worldPos);
Vector3 d1 = Vector3.Cross(s1, s2);
//第一次交换，保证前3点次序
if (d1.y < 0)
{
FrustrumPoint t = crossPoints[1];
crossPoints[1] = crossPoints[2];
crossPoints[2] = t;
}
s1 = (Vector3)(crossPoints[2].worldPos - crossPoints[1].worldPos);
s2 = (Vector3)(crossPoints[3].worldPos - crossPoints[2].worldPos);
Vector3 s3 = (Vector3)(crossPoints[0].worldPos - crossPoints[3].worldPos);
Vector3 s4 = (Vector3)(crossPoints[1].worldPos - crossPoints[0].worldPos);
d1 = Vector3.Cross(s1, s2);
Vector3 d2 = Vector3.Cross(s2, s3);
Vector3 d3 = Vector3.Cross(s3, s4);
//第二次交换，保证4点次序
if (d1.y * d2.y < 0)
{
FrustrumPoint t = crossPoints[2];
crossPoints[2] = crossPoints[1];
crossPoints[1] = t;
}
else if (d2.y * d3.y < 0)
{
FrustrumPoint t = crossPoints[3];
crossPoints[3] = crossPoints[2];
crossPoints[2] = t;
}
//最后判断是否正面朝上
s1 = (Vector3)(crossPoints[2].worldPos - crossPoints[1].worldPos);
s2 = (Vector3)(crossPoints[3].worldPos - crossPoints[2].worldPos);
d1 = Vector3.Cross(s1, s2);
if (d1.y < 0)
{
FrustrumPoint t = crossPoints[3];
crossPoints[3] = crossPoints[0];
crossPoints[0] = t;
t = crossPoints[2];
crossPoints[2] = crossPoints[1];
crossPoints[1] = t;
}
}
private bool IsSegmentIntersectOcean(int p1, int p2, float OceanLevel, ref FrustrumPoint crossPoint)
{
Vector4 a = cameraToWorld(frustrumCorner[p1]);
Vector4 b = cameraToWorld(frustrumCorner[p2]);
if ((a.y - OceanLevel) * (b.y - OceanLevel) > 0)
{
return(false); //同侧无交点
}
var p = (OceanLevel - a.y) / (b.y - a.y);
crossPoint = new FrustrumPoint();
crossPoint.worldPos = new Vector4(
a.x + p * (b.x - a.x),
OceanLevel,
a.z + p * (b.z - a.z),
1);
crossPoint.localPos = worldToCamera(crossPoint.worldPos);
return(true);
}