/// <summary>
/// 生成路径的递归函数
/// </summary>
/// <param name="lightningSegment">需要划分的线段</param>
/// <param name="fractalTime">当前递归次数</param>
/// <param name="maxFractalTime">最大递归次数</param>
/// <param name="baseAttenuation">基础衰减</param>
/// <param name="offsetRange">偏离值的范围</param>
/// <param name="direction">闪电方向</param>
/// <param name="forward">与闪电方向垂直的一个单位向量</param>
/// <param name="right">与闪电方向垂直的一个单位向量</param>
/// <param name="branchChance">生成分支的几率</param>
private void GetFractcalLightning(LightningSegment lightningSegment, int fractalTime, int maxFractalTime, float baseAttenuation, Vector2 offsetRange, Vector3 direction, Vector3 forward, Vector3 right, float branchChance = 0f)
{
if (!lightningSegment.isLeaf() || fractalTime > maxFractalTime)
{
return;
}
float zOffset = Mathf.Exp(-baseAttenuation * fractalTime) * Random.Range(offsetRange.x, offsetRange.y);
float xOffset = Mathf.Exp(-baseAttenuation * fractalTime) * Random.Range(offsetRange.x, offsetRange.y);
Vector3 mid = lightningSegment.Middle() + xOffset * right + zOffset * forward;
lightningSegment.LeftChild = new LightningSegment(lightningSegment.start, mid);
lightningSegment.LeftChild.fractal = fractalTime + 1;
lightningSegment.LeftChild.uv = lightningSegment.uv - LightningCreator.arrayForUV[lightningSegment.LeftChild.fractal];
lightningSegment.RightChild = new LightningSegment(mid, lightningSegment.end);
lightningSegment.RightChild.fractal = fractalTime + 1;
lightningSegment.RightChild.uv = lightningSegment.uv + LightningCreator.arrayForUV[lightningSegment.RightChild.fractal];
GetFractcalLightning(lightningSegment.LeftChild, fractalTime + 1, maxFractalTime, baseAttenuation, offsetRange, direction, forward, right, branchChance);
GetFractcalLightning(lightningSegment.RightChild, fractalTime + 1, maxFractalTime, baseAttenuation, offsetRange, direction, forward, right, branchChance);
if (Random.Range(0f, 1f) < branchChance)
{
//制作h形片段
zOffset = Mathf.Exp(-baseAttenuation * fractalTime) * Random.Range(offsetRange.x, offsetRange.y);
xOffset = Mathf.Exp(-baseAttenuation * fractalTime) * Random.Range(offsetRange.x, offsetRange.y);
float yOffset = Mathf.Exp(-baseAttenuation * fractalTime) * Random.Range(offsetRange.x, offsetRange.y);
Vector3 branchEnd = lightningSegment.Middle() + xOffset * right + zOffset * forward + yOffset * direction;
lightningSegment.Branch = new LightningSegment(mid, branchEnd);
lightningSegment.Branch.fractal = fractalTime + 1;
lightningSegment.Branch.uv = lightningSegment.uv + LightningCreator.arrayForUV[lightningSegment.Branch.fractal];
GetFractcalLightning(lightningSegment.Branch, fractalTime + 1, maxFractalTime, baseAttenuation, offsetRange, direction, forward, right, branchChance);
}
}
/// <summary>
/// 填充Mesh的递归函数
/// </summary>
/// <param name="lightningSegment">需要生成Mesh的线段</param>
/// <param name="vertices"></param>
/// <param name="triangle"></param>
/// <param name="uv"></param>
/// <param name="obPos">摄像机位置</param>
/// <param name="radius">当前的闪电粗细</param>
/// <param name="attenuation">分支闪电的衰减程度</param>
/// <param name="idx">顶点序号</param>
private void SegmentToMesh(LightningSegment lightningSegment, List <Vector3> vertices, List <int> triangle,
List <Vector2> uv, Vector3 obPos, float radius, float attenuation, ref int idx)
{
if (lightningSegment.isLeaf())
{
Vector3 zMid = lightningSegment.Middle();
Vector3 zNormal = Vector3.Cross(zMid - obPos, lightningSegment.end - lightningSegment.start).normalized;
var finalR = radius * attenuation;
if (lightningSegment.Branch == null)
{
//Z型片段的Mesh生成
vertices.Add(lightningSegment.start + finalR * zNormal);
vertices.Add(lightningSegment.start - finalR * zNormal);
vertices.Add(lightningSegment.end + finalR * zNormal);
vertices.Add(lightningSegment.end - finalR * zNormal);
triangle.Add(idx + 1);
triangle.Add(idx);
triangle.Add(idx + 2);
triangle.Add(idx + 1);
triangle.Add(idx + 2);
triangle.Add(idx + 3);
uv.Add(new Vector2(1, lightningSegment.uv));
uv.Add(new Vector2(0, lightningSegment.uv));
uv.Add(new Vector2(1, lightningSegment.uv));
uv.Add(new Vector2(0, lightningSegment.uv));
idx += 4;
}
}
else
{
SegmentToMesh(lightningSegment.LeftChild, vertices, triangle, uv, obPos, radius, attenuation, ref idx);
SegmentToMesh(lightningSegment.RightChild, vertices, triangle, uv, obPos, radius, attenuation, ref idx);
if (lightningSegment.Branch != null)
{
SegmentToMesh(lightningSegment.Branch, vertices, triangle, uv, obPos, radius * attenuation, attenuation, ref idx);
}
}
}
