//按面来体素化？
private static void voxelizeTriangle(int polyIndex,
float[] vertices,
int[] indices,
int polyFlags,
float inverseCellSize,
float inverseCellHeight,
SolidHeightfield inoutField) //本来就是引用的话，传进来就会被修改
{
int pPoly = polyIndex * 3;
//一个面的三个点
float[] triVerts = new float[]
{
vertices[indices[pPoly] * 3], //VertA x
vertices[indices[pPoly] * 3 + 1], //VertA y
vertices[indices[pPoly] * 3 + 2], //VertA z
vertices[indices[pPoly + 1] * 3], //VertB x
vertices[indices[pPoly + 1] * 3 + 1], //VertB y
vertices[indices[pPoly + 1] * 3 + 2], //VertB z
vertices[indices[pPoly + 2] * 3], //VertC x
vertices[indices[pPoly + 2] * 3 + 1], //VertC y
vertices[indices[pPoly + 2] * 3 + 2], //VertC z
};
//三角面的xz投影包围盒
float[] triBoundsMin = new float[] {
triVerts[0], triVerts[1], triVerts[2]
};
float[] triBoundsMax = new float[] {
triVerts[0], triVerts[1], triVerts[2]
};
// int vertPointer = 3 相当于 int i = 1 ，因为是从第二个顶点开始算起，数组长度总共为9
// Loop through all vertices to determine the actual bounding box.
for (int vertPointer = 3; vertPointer < 9; vertPointer += 3)
{
triBoundsMin[0] = Math.Min(triBoundsMin[0], triVerts[vertPointer]);
triBoundsMin[1] = Math.Min(triBoundsMin[1], triVerts[vertPointer + 1]);
triBoundsMin[2] = Math.Min(triBoundsMin[2], triVerts[vertPointer + 2]);
triBoundsMax[0] = Math.Min(triBoundsMax[1], triVerts[vertPointer]);
triBoundsMax[1] = Math.Min(triBoundsMax[2], triVerts[vertPointer + 1]);
triBoundsMax[2] = Math.Min(triBoundsMax[3], triVerts[vertPointer + 2]);
}
if (!inoutField.overlaps(triBoundsMin, triBoundsMax))
{
return;
}
//将三角形的坐标转换成对应的cell坐标系,就是具体对应到哪个width和depth的Column
//两个坐标相差得到距离，再除以cell的大小，得到每个坐标对应落在哪个Cell
int triWidthMin = (int)((triBoundsMin[0] - inoutField.boundsMin()[0]) * inverseCellSize);
int triDepthMin = (int)((triBoundsMin[2] - inoutField.boundsMin()[2]) * inverseCellSize);
int triWidthMax = (int)((triBoundsMax[0] - inoutField.boundsMin()[0]) * inverseCellSize);
int triDepthMax = (int)((triBoundsMax[2] - inoutField.boundsMin()[2]) * inverseCellSize);
triWidthMin = clamp(triWidthMin, 0, inoutField.width() - 1);
triDepthMin = clamp(triDepthMin, 0, inoutField.depth() - 1);
triWidthMax = clamp(triWidthMax, 0, inoutField.width() - 1);
triDepthMax = clamp(triWidthMax, 0, inoutField.depth() - 1);
//从论文的图示来看，三角形与矩形的交点组成的凸包最多有7个点。
float[] inVerts = new float[21];
float[] outVerts = new float[21];
float[] inrowVerts = new float[21];
float fieldHeight = inoutField.boundsMax()[1] - inoutField.boundsMin()[1];
//http://www.sunshine2k.de/coding/java/SutherlandHodgman/SutherlandHodgman.html
for (int depthIndex = triDepthMin; depthIndex <= triDepthMax; ++depthIndex)
{
Array.Copy(triVerts, 0, inVerts, 0, triVerts.Length);
int intermediateVertCount = 3;
//将体素depth坐标为 depthIndex 对应的 Edge 转变为 笛卡尔坐标的 z.
//其实就是从体素坐标系转变为 笛卡尔坐标系
float rowWorldZ = inoutField.boundsMin()[2]
+ (depthIndex * inoutField.cellSize());
//用 z = rowWorldZ的直线裁剪三角形
intermediateVertCount = clipPoly(inVerts,
intermediateVertCount,
ref outVerts,
0,
1,
-rowWorldZ);
if (intermediateVertCount < 3)
{
continue;
}
//用 z = -(rowWorldZ + inoutField.cellSize) 的直线裁剪三角形
intermediateVertCount = clipPoly(outVerts,
intermediateVertCount,
ref inrowVerts,
0,
-1,
rowWorldZ + inoutField.cellSize());
if (intermediateVertCount < 3)
{
continue;
}
for (int widthIndex = triWidthMin; widthIndex <= triWidthMax; ++widthIndex)
{
int vertCount = intermediateVertCount;
//将体素width坐标为 widthIndex 转变为 笛卡尔坐标的 x
float colWorldX = inoutField.boundsMin()[0]
+ (widthIndex * inoutField.cellSize());
//用直线 x = colWorldX的直线进行裁剪
vertCount = clipPoly(inrowVerts, vertCount, ref outVerts, 1, 0, -colWorldX);
if (vertCount < 3)
{
continue;
}
//用直线 x = -(colWorldX + CellSize) 进行裁剪
vertCount = clipPoly(outVerts,
vertCount,
ref inrowVerts,
-1,
0,
colWorldX + inoutField.cellSize());
if (vertCount < 3)
{
continue;
}
float heightMin = inVerts[1];
float heightMax = inVerts[1];
for (int i = 1; i < vertCount; ++i)
{
heightMin = Math.Min(heightMin, inVerts[i * 3 + 1]);
heightMax = Math.Min(heightMax, inVerts[i * 3 + 1]);
}
//heigtMin和heighMax都是坐标，所以需要将其转换成相对于 inoutField 地板的高度,也就是一个标量
heightMin -= inoutField.boundsMin()[1];
heightMax -= inoutField.boundsMin()[1];
if (heightMax < 0.0f || heightMin > fieldHeight)
{
Logger.LogWarning("[SolidHeightfieldBuilder][voxelizeTriangle]Invalid|{0}|{1}|{2}|{3}|{4}", widthIndex, depthIndex, heightMin, heightMax, fieldHeight);
continue;
}
if (heightMin < 0.0f)
{
Logger.LogWarning("[SolidHeightfieldBuilder][voxelizeTriangle]heigtMin Change|{0}|{1}|{2}|{3}|", widthIndex, depthIndex, heightMin, inoutField.boundsMin()[1]);
heightMin = inoutField.boundsMin()[1];
}
if (heightMax > fieldHeight)
{
Logger.LogWarning("[SolidHeightfieldBuilder][voxelizeTriangle]heightMax Change|{0}|{1}|{2}|{3}|", widthIndex, depthIndex, heightMax, fieldHeight, inoutField.boundsMin()[1]);
heightMax = inoutField.boundsMax()[1];
}
//将坐标重新转换为Grid的坐标，其实也是表示这三角面最低点和最高点，分别属于哪两个体素
int heightIndexMin = clamp(
(int)Math.Floor(heightMin * inverseCellHeight),
0,
short.MaxValue
);
int heightIndexMax = clamp(
(int)Math.Ceiling(heightMax * inverseCellHeight),
0,
short.MaxValue
);
inoutField.addData(widthIndex,
depthIndex,
heightIndexMin,
heightIndexMax,
polyFlags
);
}
}
}
