- Added rcOffsetPoly() helper function to expand polygon areas

Recast/Include/Recast.h

@@ -935,6 +935,16 @@ void rcMarkConvexPolyArea(rcContext* ctx, const float* verts, const int nverts,
 						  const float hmin, const float hmax, unsigned char areaId,
 						  rcCompactHeightfield& chf);
 
+/// Helper function to offset voncex polygons for rcMarkConvexPolyArea.
+///  @ingroup recast
+///  @param[in]		verts		The vertices of the polygon [Form: (x, y, z) * @p nverts]
+///  @param[in]		nverts		The number of vertices in the polygon.
+///  @param[out]	outVerts	The offset vertices (should hold up to 2 * @p nverts) [Form: (x, y, z) * return value]
+///  @param[in]		maxOutVerts	The max number of vertices that can be stored to @p outVerts.
+///  @returns Number of vertices in the offset polygon or 0 if too few vertices in @p outVerts.
+int rcOffsetPoly(const float* verts, const int nverts, const float offset,
+				 float* outVerts, const int maxOutVerts);
+
 /// Applies the area id to all spans within the specified cylinder.
 ///  @ingroup recast
 ///  @param[in,out]	ctx		The build context to use during the operation.

Recast/Source/RecastArea.cpp

@@ -452,6 +452,84 @@ void rcMarkConvexPolyArea(rcContext* ctx, const float* verts, const int nverts,
 	ctx->stopTimer(RC_TIMER_MARK_CONVEXPOLY_AREA);
 }
 
+int rcOffsetPoly(const float* verts, const int nverts, const float offset,
+				 float* outVerts, const int maxOutVerts)
+{
+	const float	MITER_LIMIT = 1.20f;
+
+	int n = 0;
+
+	for (int i = 0; i < nverts; i++)
+	{
+		const int a = (i+nverts-1) % nverts;
+		const int b = i;
+		const int c = (i+1) % nverts;
+		const float* va = &verts[a*3];
+		const float* vb = &verts[b*3];
+		const float* vc = &verts[c*3];
+		float dx0 = vb[0] - va[0];
+		float dy0 = vb[2] - va[2];
+		float d0 = dx0*dx0 + dy0*dy0;
+		if (d0 > 1e-6f)
+		{
+			d0 = 1.0f/rcSqrt(d0);
+			dx0 *= d0;
+			dy0 *= d0;
+		}
+		float dx1 = vc[0] - vb[0];
+		float dy1 = vc[2] - vb[2];
+		float d1 = dx1*dx1 + dy1*dy1;
+		if (d1 > 1e-6f)
+		{
+			d1 = 1.0f/rcSqrt(d1);
+			dx1 *= d1;
+			dy1 *= d1;
+		}
+		const float dlx0 = -dy0;
+		const float dly0 = dx0;
+		const float dlx1 = -dy1;
+		const float dly1 = dx1;
+		float cross = dx1*dy0 - dx0*dy1;
+		float dmx = (dlx0 + dlx1) * 0.5f;
+		float dmy = (dly0 + dly1) * 0.5f;
+		float dmr2 = dmx*dmx + dmy*dmy;
+		bool bevel = dmr2 * MITER_LIMIT*MITER_LIMIT < 1.0f;
+		if (dmr2 > 1e-6f)
+		{
+			const float scale = 1.0f / dmr2;
+			dmx *= scale;
+			dmy *= scale;
+		}
+
+		if (bevel && cross < 0.0f)
+		{
+			if (n+2 >= maxOutVerts)
+				return 0;
+			float d = (1.0f - (dx0*dx1 + dy0*dy1))*0.5f;
+			outVerts[n*3+0] = vb[0] + (-dlx0+dx0*d)*offset;
+			outVerts[n*3+1] = vb[1];
+			outVerts[n*3+2] = vb[2] + (-dly0+dy0*d)*offset;
+			n++;
+			outVerts[n*3+0] = vb[0] + (-dlx1-dx1*d)*offset;
+			outVerts[n*3+1] = vb[1];
+			outVerts[n*3+2] = vb[2] + (-dly1-dy1*d)*offset;
+			n++;
+		}
+		else
+		{
+			if (n+1 >= maxOutVerts)
+				return 0;
+			outVerts[n*3+0] = vb[0] - dmx*offset;
+			outVerts[n*3+1] = vb[1];
+			outVerts[n*3+2] = vb[2] - dmy*offset;
+			n++;
+		}
+	}
+	
+	return n;
+}
+
+
 /// @par
 ///
 /// The value of spacial parameters are in world units.

RecastDemo/Include/ConvexVolumeTool.h

@@ -27,6 +27,7 @@ class ConvexVolumeTool : public SampleTool
 {
 	Sample* m_sample;
 	int m_areaType;
+	float m_polyOffset;
 	float m_boxHeight;
 	float m_boxDescent;
 	

RecastDemo/Source/ConvexVolumeTool.cpp

@@ -101,6 +101,7 @@ static int pointInPoly(int nvert, const float* verts, const float* p)
 ConvexVolumeTool::ConvexVolumeTool() :
 	m_sample(0),
 	m_areaType(SAMPLE_POLYAREA_GRASS),
+	m_polyOffset(0.0f),
 	m_boxHeight(6.0f),
 	m_boxDescent(1.0f),
 	m_npts(0),
@@ -127,6 +128,7 @@ void ConvexVolumeTool::handleMenu()
 {
 	imguiSlider("Shape Height", &m_boxHeight, 0.1f, 20.0f, 0.1f);
 	imguiSlider("Shape Descent", &m_boxDescent, 0.1f, 20.0f, 0.1f);
+	imguiSlider("Poly Offset", &m_polyOffset, 0.0f, 10.0f, 0.1f);
 
 	imguiSeparator();
 
@@ -196,7 +198,17 @@ void ConvexVolumeTool::handleClick(const float* /*s*/, const float* p, bool shif
 				minh -= m_boxDescent;
 				maxh = minh + m_boxHeight;
 
-				geom->addConvexVolume(verts, m_nhull, minh, maxh, (unsigned char)m_areaType);
+				if (m_polyOffset > 0.01f)
+				{
+					float offset[MAX_PTS*2*3];
+					int noffset = rcOffsetPoly(verts, m_nhull, m_polyOffset, offset, MAX_PTS*2);
+					if (noffset > 0)
+						geom->addConvexVolume(offset, noffset, minh, maxh, (unsigned char)m_areaType);
+				}
+				else
+				{
+					geom->addConvexVolume(verts, m_nhull, minh, maxh, (unsigned char)m_areaType);
+				}
 			}
 			
 			m_npts = 0;