recastnavigation.Sample_TempObstacles代码注解 – rcBuildHeightfieldLayers

烘培代码在 rcBuildHeightfieldLayers

本质上是为每个tile生成高度上的不同layer

算法的关键是三层循环:

for z 轴循环

for x 轴循环

for 高度span 循环

判断span和相邻span的连通性(x/z平面相邻cell)

如果联通, 则标注为同一个layer, 也就是在x/z平面上标注layer, 形成像是互不相交的面包片叠放的样子, 也有有坡度的layer

 

然后做了一些layer合并处理, 相邻的layer且在x/z平面不重叠且合并后高度差较小的, 可以合并为一个layer

 

同时layer记录了当前layer的上下高度范围, 边界(坐标系), 边界(体素),

heights记录了layer内每个span相对于layer的体素下边界的高度差(体素单位)

areas记录了layer内每个span的areas

cons记录了layer和span的相邻关系

 

 

(注意代码里改了一些变量的命名, 过于简化的变量名不利于新手看懂代码)

(另外, 代码里把y改成了z, recast本身代码里体素遍历都是 x/y平面, 按Unity习惯, 改成了 x/z 平面遍历, y代表高度)

/// See the #rcConfig documentation for more information on the configuration parameters. ///  /// @see rcAllocHeightfieldLayerSet, rcCompactHeightfield, rcHeightfieldLayerSet, rcConfig bool rcBuildHeightfieldLayers(rcContext* ctx, rcCompactHeightfield& chf, 							  const int borderSize, const int walkableHeight, 							  rcHeightfieldLayerSet& lset) { 	rcAssert(ctx); 	 	rcScopedTimer timer(ctx, RC_TIMER_BUILD_LAYERS); 	 	const int w = chf.width; 	const int h = chf.height; 	 	rcScopedDelete<unsigned char> srcReg((unsigned char*)rcAlloc(sizeof(unsigned char)*chf.spanCount, RC_ALLOC_TEMP)); 	if (!srcReg) 	{ 		ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'srcReg' (%d).", chf.spanCount); 		return false; 	} 	memset(srcReg,0xff,sizeof(unsigned char)*chf.spanCount); 	 	const int nsweeps = chf.width; 	rcScopedDelete<rcLayerSweepSpan> sweeps((rcLayerSweepSpan*)rcAlloc(sizeof(rcLayerSweepSpan)*nsweeps, RC_ALLOC_TEMP)); 	if (!sweeps) 	{ 		ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'sweeps' (%d).", nsweeps); 		return false; 	} 	 	 	// Partition walkable area into monotone regions. 	int prevCount[256]; 	unsigned char regId = 0;  	//注意这里是三层循环: 	// for z 平面 	//		for x 平面 	//			for y 平面 (高度) 	// 最内层是对每个y平面的处理, 在每个y层面上根据span在x/z的连接性做region分配和合并, 也就是layer的意义: 按高度分层. 像是切片面包. 	// 从3d视角看是, 遍历x/z平面的每个cell, 依次检查当前cell与相邻cell在高度上的切片span是否有联通的, 如果有联通就把x/z平面相邻的cell上region赋值为相同id. 让x/z平面形成region.高度上 	for (int z = borderSize; z < h-borderSize; ++z) 	{ 		// prevCount 记录的是当前x轴上的sweep和上一轮x循环(-z方向)的region相连的span数量. 		memset(prevCount,0,sizeof(int)*regId); 		//(按行扫描编号), 这个编号在y的循环体内, 也就是每扫描一行x则重置, 扫描完一行后后面会把sweepId变成regionId, 所以重置没问题. 		unsigned char nowSweepId = 0;  		 		for (int x = borderSize; x < w-borderSize; ++x) 		{ 			const rcCompactCell& c = chf.cells[x+z*w]; 			 			for (int i = (int)c.index, ni = (int)(c.index+c.count); i < ni; ++i) 			{ 				const rcCompactSpan& s = chf.spans[i]; 				if (chf.areas[i] == RC_NULL_AREA) continue;  				unsigned char sweepId = 0xff;  				//(-1, 0)方向如果有连接 				// -x 				if (rcGetCon(s, 0) != RC_NOT_CONNECTED) 				{ 					const int ax = x + rcGetDirOffsetX(0); 					const int ay = z + rcGetDirOffsetY(0); 					const int ai = (int)chf.cells[ax+ay*w].index + rcGetCon(s, 0); 					//如果连接的不是NULL_AREA且它的sweepId并不是未初始化状态(未设置, 默认值0xff) (sweepId存储在srcReg里) 					//那么把自己的sweepId也设置为相邻这个span的sweepId,因为是从左到右遍历, 所以-x是刚刚遍历过的,如果连接(x轴相邻的span)且有srcReg, 则设置为相同srcReg  					if (chf.areas[ai] != RC_NULL_AREA && srcReg[ai] != 0xff)  						sweepId = srcReg[ai];									 				} 				 				// 如果和左侧相邻span(-1, 0)没有连接, 或者连接的area是NULL, 或者sweepId无效, 则把自己的sweepId设置为新的id. (新分配一个扫描编号) 				if (sweepId == 0xff) 				{ 					sweepId = nowSweepId++; 					sweeps[sweepId].nei = 0xff; 					sweeps[sweepId].ns = 0; 				} 				 				// 检查完-x方向. 再检查之前扫描过的z方向的邻居 (上一轮扫描过的) 				// 如果相连且sweepId不是0xff, 则判断是不是刚刚x方向新加的sweepId(还没邻居), 如果是则把z方向的这个邻居设置成自己的邻居 				// 如果当前邻居是z方向的这个span, 则把ns++, 把邻居sweepId记录的数量也加1(prevCount[nrSweepId]++) 				// 如果当前邻居不是z方向这个span, 说明和-z这一行有两个邻居, 则把邻居置为无效值  				// (0, -1) x/z平面的下面 -> -z, 注意源码是 x/y 平面, 这里原本注释写的 -y 				if (rcGetCon(s,3) != RC_NOT_CONNECTED) 				{ 					const int ax = x + rcGetDirOffsetX(3); 					const int ay = z + rcGetDirOffsetY(3); 					const int ai = (int)chf.cells[ax+ay*w].index + rcGetCon(s, 3); 					const unsigned char nrRegId = srcReg[ai]; 					if (nrRegId != 0xff) 					{ 						// Set neighbour when first valid neighbour is encoutered. 						if (sweeps[sweepId].ns == 0) 							sweeps[sweepId].nei = nrRegId; 						 						if (sweeps[sweepId].nei == nrRegId) 						{ 							// Update existing neighbour 							sweeps[sweepId].ns++; 							prevCount[nrRegId]++; 						} 						else 						{ 							// This is hit if there is nore than one neighbour. 							// Invalidate the neighbour. 							sweeps[sweepId].nei = 0xff; 						} 					} 				} 				 				srcReg[i] = sweepId; 			} 		} 		 		// Create unique ID. 		for (int i = 0; i < nowSweepId; ++i) 		{ 			/// 如果邻居设置了, 而且邻居连接我的数量和我数量相同则说明我们是完全相临的, 可以合并, 否则意味着我的邻居可能还有其他sweepId和他相连.  			/// 类似下面, A先扫描完, 形成了一个完整连续的region=1, 再遍历B时, prevCount[1] = 4, (A行3个1和1个2), 但是sweeps[1] = 3, (B行3个1) 			/// 所以此时B行里的1和A行里的1不能合并了. 要给B行的1分配新的regionId 			///  			///   <--- -x方向(左) 			///                             | 			/// B: [1] [1] [1]     [2]      |     -> 此处的1, 2都还是sweepId, 代表从左到右的扫描分割序号. 			/// A: [1] [1] [1] [1] [1]      |     -> 此时的1已经是regionId了. 			///                           -z方向(下) 			///  			///  			/// B: [1] [1]               | 			/// A: [1] [1] [1]           |     -> 这种情况可以合并,  prevCount[A1].nei = 2, sweeps[B1].ns = 2 			///  			/// B: [1] [1] [1] [1]       | 			/// A: [1] [1] [1]           |     -> 这种情况也可以合并,  prevCount[A1].nei = 3, sweeps[B1].ns = 3, (B第四个[1]因为和下面无连接, 所以两边都不计数) 			///  			/// If the neighbour is set and there is only one continuous connection to it, 			/// the sweep will be merged with the previous one, else new region is created. 			if (sweeps[i].nei != 0xff && prevCount[sweeps[i].nei] == (int)sweeps[i].ns) 			{ 				sweeps[i].id = sweeps[i].nei; 			} 			else 			{ 				if (regId == 255) 				{ 					ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Region ID overflow."); 					return false; 				} 				sweeps[i].id = regId++; 			} 		} 		 		// 之前srcReg里记录的是sweepId, 现在改回regionId 		// Remap local sweep ids to region ids. 		for (int x = borderSize; x < w-borderSize; ++x) 		{ 			const rcCompactCell& c = chf.cells[x+z*w]; 			for (int i = (int)c.index, ni = (int)(c.index+c.count); i < ni; ++i) 			{ 				if (srcReg[i] != 0xff) 					srcReg[i] = sweeps[srcReg[i]].id; 			} 		} 	}  	// Allocate and init layer regions. 	const int nregs = (int)regId; 	rcScopedDelete<rcLayerRegion> regs((rcLayerRegion*)rcAlloc(sizeof(rcLayerRegion)*nregs, RC_ALLOC_TEMP)); 	if (!regs) 	{ 		ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'regs' (%d).", nregs); 		return false; 	} 	memset(regs, 0, sizeof(rcLayerRegion)*nregs); 	for (int i = 0; i < nregs; ++i) 	{ 		regs[i].layerId = 0xff; 		regs[i].ymin = 0xffff; 		regs[i].ymax = 0; 	} 	 	// Find region neighbours and overlapping regions. 	for (int z = 0; z < h; ++z) //遍历 z 	{ 		for (int x = 0; x < w; ++x) //遍历 x/z 平面 		{ 			const rcCompactCell& c = chf.cells[x+z*w]; 			 			//记录y方向的区域id和数量 			unsigned char lregs[RC_MAX_LAYERS]; 			int nlregs = 0; 			 			for (int i = (int)c.index, ni = (int)(c.index+c.count); i < ni; ++i) //遍历 y 方向 span 			{ 				const rcCompactSpan& s = chf.spans[i]; 				const unsigned char regionId = srcReg[i]; 				if (regionId == 0xff) continue; //跳过没有区域的span 				 				regs[regionId].ymin = rcMin(regs[regionId].ymin, s.y); 				regs[regionId].ymax = rcMax(regs[regionId].ymax, s.y); 				 				// Collect all region layers. 				if (nlregs < RC_MAX_LAYERS) 					lregs[nlregs++] = regionId; 				 				// Update neighbours 				// 遍历4个方向, 记录邻居区域信息 (和自己不同区域) 				for (int dir = 0; dir < 4; ++dir) 				{ 					if (rcGetCon(s, dir) != RC_NOT_CONNECTED) 					{ 						const int ax = x + rcGetDirOffsetX(dir); 						const int ay = z + rcGetDirOffsetY(dir); 						const int ai = (int)chf.cells[ax+ay*w].index + rcGetCon(s, dir); 						const unsigned char nrReg = srcReg[ai];  						if (nrReg != 0xff && nrReg != regionId) //邻居的region 和 自己不一样 						{ 							// Don't check return value -- if we cannot add the neighbor 							// it will just cause a few more regions to be created, which 							// is fine. 							addUnique(regs[regionId].neis, regs[regionId].nneis, RC_MAX_NEIS, nrReg); 						} 					} 				} 				 			} 			 			// 两层遍历高度(y)方向的区域 (两两检查),  			// Update overlapping regions. 			for (int i = 0; i < nlregs-1; ++i) 			{ 				for (int j = i+1; j < nlregs; ++j) 				{ 					if (lregs[i] != lregs[j]) 					{ 						rcLayerRegion& ri = regs[lregs[i]]; 						rcLayerRegion& rj = regs[lregs[j]];  						//在两个region的layers里记录该region在x/z平面上重叠的其他高度的regionId. 用于索引高度上的不同层. 						if (!addUnique(ri.layers, ri.nlayers, RC_MAX_LAYERS, lregs[j]) || 							!addUnique(rj.layers, rj.nlayers, RC_MAX_LAYERS, lregs[i])) 						{ 							ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: layer overflow (too many overlapping walkable platforms). Try increasing RC_MAX_LAYERS."); 							return false; 						} 					} 				} 			} 			 		} 	} 	 	// Create 2D layers from regions. 	unsigned char layerId = 0; 	 	static const int MAX_STACK = 64; 	unsigned char stack[MAX_STACK]; 	int nstack = 0; 	 	for (int i = 0; i < nregs; ++i) 	{ 		rcLayerRegion& root = regs[i]; 		// Skip already visited. 		if (root.layerId != 0xff) 			continue;  		// Start search. 		// 分配 layerId 		root.layerId = layerId; 		root.base = 1; 		 		nstack = 0; 		stack[nstack++] = (unsigned char)i; //region序号入栈 		 		while (nstack) 		{ 			// Pop front 			rcLayerRegion& reg = regs[stack[0]]; 			nstack--; 			for (int j = 0; j < nstack; ++j) //移除stack第一个元素. 				stack[j] = stack[j+1]; 			 			const int nneis = (int)reg.nneis; 			for (int j = 0; j < nneis; ++j) 			{ 				const unsigned char nei = reg.neis[j]; 				rcLayerRegion& nrReg = regs[nei]; 				// Skip already visited. 				if (nrReg.layerId != 0xff) 					continue; 				// Skip if the neighbour is overlapping root region. 				// 跳过 邻居是x/z重叠的不同高度的region 				if (contains(root.layers, root.nlayers, nei)) 					continue; 				// Skip if the height range would become too large. 				// 如果两个区域加起来的高度落差太大 跳过 (因为高度差不大的情况下会合并layer, 但是合并太多后会导致layer上下表面的高差越来越大, 这时候就要打断合并了) 				const int ymin = rcMin(root.ymin, nrReg.ymin); 				const int ymax = rcMax(root.ymax, nrReg.ymax); 				if ((ymax - ymin) >= 255) 					 continue;  				if (nstack < MAX_STACK) 				{ 					// Deepen 邻居入栈 					stack[nstack++] = (unsigned char)nei; 					 					// Mark layer id 					// 将邻居的layerId设置为自己的layerId. 合并成一个layer 					nrReg.layerId = layerId; 					// Merge current layers to root. 					// 将邻居的高度layers也合并到自己的layers, (合并成一个layer了, 高度重叠区域信息也要合并). 					for (int k = 0; k < nrReg.nlayers; ++k) 					{ 						if (!addUnique(root.layers, root.nlayers, RC_MAX_LAYERS, nrReg.layers[k])) 						{ 							ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: layer overflow (too many overlapping walkable platforms). Try increasing RC_MAX_LAYERS."); 							return false; 						} 					} 					root.ymin = rcMin(root.ymin, nrReg.ymin); // 更新合并后的layer上下表面. 					root.ymax = rcMax(root.ymax, nrReg.ymax); 				} 			} 		} 		 		layerId++; 	} 	 	// Merge non-overlapping regions that are close in height. 	// 合并高度上差异不大, 而且没有重叠的区域, 楼梯, 坡等  	const unsigned short mergeHeight = (unsigned short)walkableHeight * 4; 	 	for (int i = 0; i < nregs; ++i) 	{ 		rcLayerRegion& ri = regs[i]; 		if (!ri.base) continue; //只需要查询layer的 base region 		 		unsigned char newId = ri.layerId; 		 		for (;;) 		{ 			unsigned char oldId = 0xff; 			 			for (int j = 0; j < nregs; ++j)  //双层遍历 region 两两计算 			{ 				if (i == j) continue; 				rcLayerRegion& rj = regs[j]; 				if (!rj.base) continue; 				 				// Skip if the regions are not close to each other. 				// 两个区域的上下表面+合并高差 不重叠, 则无法合并 				if (!overlapRange(ri.ymin,ri.ymax+mergeHeight, rj.ymin,rj.ymax+mergeHeight)) 					continue; 				// Skip if the height range would become too large. 				const int ymin = rcMin(ri.ymin, rj.ymin); 				const int ymax = rcMax(ri.ymax, rj.ymax); 				if ((ymax - ymin) >= 255) //合并后高差太大 跳过 				  continue; 						   				// Make sure that there is no overlap when merging 'ri' and 'rj'. 				bool overlap = false; 				// Iterate over all regions which have the same layerId as 'rj' 				for (int k = 0; k < nregs; ++k) 				{ 					if (regs[k].layerId != rj.layerId) 						continue; 					// Check if region 'k' is overlapping region 'ri' 					// Index to 'regs' is the same as region id. 					// 和j相同layerId的区域, 判断是否和ri有重叠, 如果有重叠说明合并regionI 和 regionJ 后会导致用一个region在x/z平面出现重叠. 所以此时要break. 不能合并 					if (contains(ri.layers,ri.nlayers, (unsigned char)k)) 					{ 						overlap = true; 						break; 					} 				} 				// Cannot merge of regions overlap. 				if (overlap) 					continue; 				 				// Can merge i and j. 				oldId = rj.layerId; 				break; 			} 			 			// Could not find anything to merge with, stop. 			if (oldId == 0xff) 				break; 			 			// Merge 			for (int j = 0; j < nregs; ++j) 			{ 				rcLayerRegion& rj = regs[j]; 				if (rj.layerId == oldId) 				{ 					rj.base = 0; 					// Remap layerIds. 					rj.layerId = newId; 					// Add overlaid layers from 'rj' to 'ri'. 					// 合并之后, 同样也需要 将邻居的高度layers也合并到自己的layers, (合并成一个layer了, 高度重叠区域信息也要合并). 					for (int k = 0; k < rj.nlayers; ++k) 					{ 						if (!addUnique(ri.layers, ri.nlayers, RC_MAX_LAYERS, rj.layers[k])) 						{ 							ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: layer overflow (too many overlapping walkable platforms). Try increasing RC_MAX_LAYERS."); 							return false; 						} 					}  					// Update height bounds. 					ri.ymin = rcMin(ri.ymin, rj.ymin); // 更新合并后的layer上下表面. 					ri.ymax = rcMax(ri.ymax, rj.ymax); 				} 			} 		} 	} 	 	// 合并后layerId不连续了, 所以这里要重新remap下, 保持layerId连续 	// Compact layerIds 	unsigned char remap[256]; 	memset(remap, 0, 256);  	// Find number of unique layers. 	layerId = 0; 	for (int i = 0; i < nregs; ++i) 		remap[regs[i].layerId] = 1; 	for (int oldLayerId = 0; oldLayerId < 256; ++oldLayerId) 	{ 		if (remap[oldLayerId]) 			remap[oldLayerId] = layerId++; 		else 			remap[oldLayerId] = 0xff; 	} 	// Remap ids. 	for (int i = 0; i < nregs; ++i) 		regs[i].layerId = remap[regs[i].layerId]; //从remap里查询oldLayerId对应的新layerId, 并赋值 	 	// No layers, return empty. 	if (layerId == 0) 		return true; 	 	// Create layers. 	rcAssert(lset.layers == 0); 	 	const int lw = w - borderSize*2; 	const int lh = h - borderSize*2;  	// Build contracted bbox for layers. 	float bmin[3], bmax[3]; 	rcVcopy(bmin, chf.bmin); 	rcVcopy(bmax, chf.bmax); 	bmin[0] += borderSize*chf.cs; 	bmin[2] += borderSize*chf.cs; 	bmax[0] -= borderSize*chf.cs; 	bmax[2] -= borderSize*chf.cs; 	 	lset.nlayers = (int)layerId; 	 	lset.layers = (rcHeightfieldLayer*)rcAlloc(sizeof(rcHeightfieldLayer)*lset.nlayers, RC_ALLOC_PERM); 	if (!lset.layers) 	{ 		ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'layers' (%d).", lset.nlayers); 		return false; 	} 	memset(lset.layers, 0, sizeof(rcHeightfieldLayer)*lset.nlayers);  	 	// Store layers. 	for (int i = 0; i < lset.nlayers; ++i) 	{ 		unsigned char curId = (unsigned char)i;  		rcHeightfieldLayer* layer = &lset.layers[curId];  		const int gridSize = sizeof(unsigned char)*lw*lh; //体素x/z空间size, 二维数组长度  		layer->heights = (unsigned char*)rcAlloc(gridSize, RC_ALLOC_PERM); 		if (!layer->heights) 		{ 			ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'heights' (%d).", gridSize); 			return false; 		} 		memset(layer->heights, 0xff, gridSize);  		layer->areas = (unsigned char*)rcAlloc(gridSize, RC_ALLOC_PERM); 		if (!layer->areas) 		{ 			ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'areas' (%d).", gridSize); 			return false; 		} 		memset(layer->areas, 0, gridSize);  		layer->cons = (unsigned char*)rcAlloc(gridSize, RC_ALLOC_PERM); 		if (!layer->cons) 		{ 			ctx->log(RC_LOG_ERROR, "rcBuildHeightfieldLayers: Out of memory 'cons' (%d).", gridSize); 			return false; 		} 		memset(layer->cons, 0, gridSize); 		 		// Find layer height bounds. 		int hmin = 0, hmax = 0; //上下表面高度 (体素单位) 		for (int j = 0; j < nregs; ++j) 		{ 			if (regs[j].base && regs[j].layerId == curId) 			{ 				hmin = (int)regs[j].ymin; 				hmax = (int)regs[j].ymax; //此处应该可以break ? 			} 		}  		layer->width = lw; 		layer->height = lh; 		layer->cs = chf.cs; 		layer->ch = chf.ch; 		 		// Adjust the bbox to fit the heightfield. 		rcVcopy(layer->bmin, bmin); 		rcVcopy(layer->bmax, bmax); 		layer->bmin[1] = bmin[1] + hmin*chf.ch; //体素高度转坐标高度 		layer->bmax[1] = bmin[1] + hmax*chf.ch; 		layer->hmin = hmin; 		layer->hmax = hmax;  		// Update usable data region. 		layer->minx = layer->width; 		layer->maxx = 0; 		layer->miny = layer->height; 		layer->maxy = 0; 		 		// Copy height and area from compact heightfield.  		for (int z = 0; z < lh; ++z) 		{ 			for (int x = 0; x < lw; ++x) 			{ 				const int cx = borderSize+x; 				const int cz = borderSize+z; 				const rcCompactCell& c = chf.cells[cx+cz*w]; 				for (int j = (int)c.index, nj = (int)(c.index+c.count); j < nj; ++j) 				{ 					const rcCompactSpan& span = chf.spans[j]; 					// Skip unassigned regions. 					if (srcReg[j] == 0xff) 						continue; 					// Skip of does nto belong to current layer. 					unsigned char lid = regs[srcReg[j]].layerId; 					if (lid != curId) 						continue; 					 					// Update data bounds. 					layer->minx = rcMin(layer->minx, x); 					layer->maxx = rcMax(layer->maxx, x); 					layer->miny = rcMin(layer->miny, z); 					layer->maxy = rcMax(layer->maxy, z); 					 					// Store height and area type. 					const int idx = x+z*lw; 					layer->heights[idx] = (unsigned char)(span.y - hmin); 					layer->areas[idx] = chf.areas[j]; 					 					// Check connection. 					unsigned char portal = 0; 					unsigned char con = 0; 					for (int dir = 0; dir < 4; ++dir) 					{ 						if (rcGetCon(span, dir) != RC_NOT_CONNECTED) 						{ 							const int ax = cx + rcGetDirOffsetX(dir); 							const int ay = cz + rcGetDirOffsetY(dir); 							const int ai = (int)chf.cells[ax+ay*w].index + rcGetCon(span, dir); 							unsigned char alid = srcReg[ai] != 0xff ? regs[srcReg[ai]].layerId : 0xff; 							// Portal mask 							if (chf.areas[ai] != RC_NULL_AREA && lid != alid) 							{ 								portal |= (unsigned char)(1<<dir); 								// Update height so that it matches on both sides of the portal. 								const rcCompactSpan& as = chf.spans[ai]; 								if (as.y > hmin) 									layer->heights[idx] = rcMax(layer->heights[idx], (unsigned char)(as.y - hmin)); 							} 							// Valid connection mask 							// 相邻的同layer的span连接信息记录在 cons的低4位. (上下左右) 							if (chf.areas[ai] != RC_NULL_AREA && lid == alid) 							{ 								const int nx = ax - borderSize; 								const int ny = ay - borderSize; 								if (nx >= 0 && ny >= 0 && nx < lw && ny < lh) 									con |= (unsigned char)(1<<dir); 							} 						} 					} 					 					layer->cons[idx] = (portal << 4) | con; //相邻的不同layer的信息记录在cons的高4位. 				} 			} 		} 		 		if (layer->minx > layer->maxx) 			layer->minx = layer->maxx = 0; 		if (layer->miny > layer->maxy) 			layer->miny = layer->maxy = 0; 	} 	 	return true; } 

　　

有两个文档也可以看一下, 看懂了上面的代码再去看文章就清楚多了. 如果不好理解代码. 可以结合文章图例一起看. 代码注释已经非常详细了, 只是没有图例

https://blog.csdn.net/zstu_zy/article/details/97247013

https ://www.jianshu.com/p/f6cd9b7696f6