/// <summary>
/// 构建八叉树
/// </summary>
public static Octree Build(TreeModel treeModel)
{
GameObject root = treeModel.TreeModelInstance; //获取根节点表示的模型
if (root == null)
{
return(null);
}
/*
* 添加包含整个植物的包围盒
* 八叉树则以该包围盒为根节点进行构建
*/
Mesh.AddBoxColliderInParent(root);
Bounds rootBounds = root.GetComponent <Collider>().bounds;
if (IsEmpty(rootBounds))
{
return(null);
}
List <Triangle> triangles = GameObjectOperation.GetTreeTriangles(treeModel);
if (triangles == null || triangles.Count == 0)
{
return(null);
}
return(new Octree(rootBounds.center, rootBounds.size, GameObjectOperation.GetTreeTriangles(treeModel), 5));
}
/// <summary>
/// 模拟天空散射
/// </summary>
/// <param name="SolarDayAngle_Deg">太阳日角</param>
/// <param name="SolarAltitude_Deg">太阳高度角</param>
/// <param name="StartHour">开始的时间</param>
/// <param name="EndHour">结束的时间</param>
/// <param name="_Octree">八叉树</param>
/// <param name="LatitudeNum">纬度方向的剖分个数</param>
/// <param name="LongtitudeNum">经度度方向的剖分个数</param>
public static void ScatterLightSimulation(TreeModel treeModel, double SolarDayAngle_Rad, double SolarAltitude_Deg, double StartHour, double EndHour, Octree _Octree, int LatitudeNum, int LongtitudeNum)
{
Triangle[] TreeTriangles = GameObjectOperation.GetTreeTriangles(treeModel).ToArray(); //获取所有的三角面片
double _ScatterIrradiance = ScatterIrradiance(SolarDayAngle_Rad, SolarAltitude_Deg, _Octree.Root.Bounds.center.y); //总散射辐射度
LightCastHemisphere LightHemisphere = null;
for (int i = 0; i < TreeTriangles.Length; i++)
{
if (TreeTriangles[i].Type != OrganType.Leaf)
{
continue; //非叶片，无需计算散射辐射
}
/*
* 优化
* 限定天穹半球的大小
* 每次三角面片，天穹半球跟随三角面片移动，无需重新计算
*/
if (LightHemisphere == null)
{
LightHemisphere = new LightCastHemisphere(TreeTriangles[i].Center, _Octree.Root.Bounds);
}
else
{
LightHemisphere.MoveTo(TreeTriangles[i].Center);
}
/*
* 通过天穹半球计算出天空散射透过率
* 该面片上的平均散射辐射度（W / m^2） = 天空散射透过率 * 总散射辐射度
* 该面片上的总辐射度(W) = 平均散射辐射度 * 该面片的面积
* 注意：因为存在透明的纹理，因此需要再得到整个叶片模型的散射能量的基础上，再乘以非透明的比例，才能得到真正的散射能量
*/
LeafIndex _LeafIndex = TreeTriangles[i].Index as LeafIndex;
_LeafIndex.ModelScatterEnergy += (float)(LightHemisphere.GetSkyTransmissivity(LongtitudeNum, LatitudeNum, TreeTriangles, i) * _ScatterIrradiance * TreeTriangles[i].Area());
}
}