/// <summary>
/// 对贴花的模型重新映射UV
/// </summary>
/// <param name="decalMesh"></param>
/// <param name="decalNormal"></param>
/// <returns></returns>
/// <remarks>UV展开算法需要进一步研究，这里使用最基本的算法</remarks>
private Mesh RemapDecalMapUV(Mesh decalMesh, Vector3 decalNormal)
{
List <Mapped2DVector> vertexMappedTo2DList = new List <Mapped2DVector>();
float xMin = float.MaxValue;
float yMin = float.MaxValue;
float xMax = float.MinValue;
float yMax = float.MinValue;
Vector2[] mappedUV = new Vector2[decalMesh.uv.Length];
for (int i = 0; i < decalMesh.vertexCount; ++i)
{
Vector3 vertexPosition = decalMesh.vertices[i];
Mapped2DVector posMapTo2D = Mapped2DVector.MapVector3ToVector2(vertexPosition, decalNormal);
xMin = Mathf.Min(xMin, posMapTo2D.MappedVector2.x);
xMax = Mathf.Max(xMax, posMapTo2D.MappedVector2.x);
yMin = Mathf.Min(yMin, posMapTo2D.MappedVector2.y);
yMax = Mathf.Max(yMax, posMapTo2D.MappedVector2.y);
vertexMappedTo2DList.Add(posMapTo2D);
}
float uSize = xMax - xMin;
float vSize = yMax - yMin;
for (int i = 0; i < vertexMappedTo2DList.Count; ++i)
{
Mapped2DVector mapped2DVector = vertexMappedTo2DList[i];
float u = (mapped2DVector.MappedVector2.x - xMin) / uSize;
float v = 1 - (mapped2DVector.MappedVector2.y - yMin) / vSize; //MapVector3ToVector2里的y坐标系是向下的，与正常uv的相反
mappedUV[i] = new Vector2(u, v);
}
decalMesh.uv = mappedUV;
return(decalMesh);
}
/// <summary>
/// Andrew monotone chain算法，计算凸边形
/// </summary>
/// <param name="inVertices">输入的无序3维点</param>
/// <param name="uAxis">降维x方向</param>
/// <param name="vAxis">降维y方向</param>
/// <param name="convexHullVertices">输出凸边形顶点</param>
/// <param name="triangles">triangle indices</param>
/// <param name="uvs">输出uv</param>
/// <returns></returns>
public static bool CreateConvexHullByMonotoneChain(List <Vector3> inVertices, Vector3 uAxis, Vector3 vAxis, out Vector3[] convexHullVertices, out Vector2[] uvs, out int[] triangles, TriangleWindingOrder triangleWindingOrder = TriangleWindingOrder.CounterClockWise)
{
convexHullVertices = new Vector3[0];
uvs = new Vector2[0];
triangles = new int[0];
if (inVertices.Count < 3)
{
return(false);
}
float uMax = float.MinValue;
float uMin = float.MaxValue;
float vMax = float.MinValue;
float vMin = float.MaxValue;
//3D降维到2D
Dictionary <Vector2, Mapped2DVector> vector2DAndMappedDict = new Dictionary <Vector2, Mapped2DVector>();
for (int i = 0; i < inVertices.Count; ++i)
{
Mapped2DVector mappedVector = new Mapped2DVector(inVertices[i], uAxis, vAxis);
if (!vector2DAndMappedDict.ContainsKey(mappedVector.MappedVector2))
{
vector2DAndMappedDict.Add(mappedVector.MappedVector2, mappedVector);
uMax = Mathf.Max(uMax, mappedVector.MappedVector2.x);
uMin = Mathf.Min(uMin, mappedVector.MappedVector2.x);
vMax = Mathf.Max(vMax, mappedVector.MappedVector2.y);
vMin = Mathf.Min(vMin, mappedVector.MappedVector2.y);
}
}
List <Vector2> inVertexPoints = vector2DAndMappedDict.Keys.ToList();
List <Vector2> convexHullByMonotoneChain = MonotoneChain(inVertexPoints.ToArray()).ToList();
convexHullVertices = new Vector3[convexHullByMonotoneChain.Count];
uvs = new Vector2[convexHullByMonotoneChain.Count];
//计算uv
for (int i = 0; i < convexHullByMonotoneChain.Count; ++i)
{
Vector2 point2D = convexHullByMonotoneChain[i];
convexHullVertices[i] = vector2DAndMappedDict[point2D].OriginalVector;
Vector2 pointUV = new Vector2();
pointUV.x = MathUtils.Remap(point2D.x, uMax, uMin, 1, 0);
pointUV.y = MathUtils.Remap(point2D.y, vMax, vMin, 1, 0);
uvs[i] = pointUV;
}
//根据WindingOrder计算triangle
int index = 1;
triangles = new int[(convexHullByMonotoneChain.Count - 2) * 3];
for (int i = 0; i < triangles.Length; i += 3)
{
triangles[i] = 0;
if (triangleWindingOrder == TriangleWindingOrder.CounterClockWise)
{
triangles[i + 1] = index;
triangles[i + 2] = index + 1;
}
else
{
triangles[i + 1] = index + 1;
triangles[i + 2] = index;
}
index++;
}
return(true);
}