示例 2：确定标准显示对象的隐藏线

将眼坐标线段转换为显示空间

1. 如果视图具有强制修剪平面，请将眼坐标线段修剪到这些平面上。
2. 如果透视处于打开状态，则执行从眼睛坐标到透视的转换。

如果您使用的是 ,,, 或函数，则应调用以建立实体的边界框。这将使 AutoCAD 知道实体需要多少空间并在 ZOOM 扩展数据块中使用。当实体处于世界坐标中时，通常调用该函数，以确定适合世界坐标中实体的最小框。polygonEye()polygonDc()polylineEye()polylineDc()AcGiViewportGeometryAcGiWorldGeometry::setExtents()setExtents()

 AsdkViewGeomSamp::AsdkViewGeomSamp() : mNumVerts(4) 
 { 
 mVerts[0] = AcGePoint3d(0.0, 0.0, 0.0); 
 mVerts[1] = AcGePoint3d(1.0, 0.0, 0.0); 
 mVerts[2] = AcGePoint3d(0.0, 1.0, 0.0); 
 mVerts[3] = AcGePoint3d(0.0, 0.0, 1.0); 
 } 
  
  
 Acad::ErrorStatus 
 AsdkViewGeomSamp::subTransformBy(const AcGeMatrix3d &xfm) 
 { 
 assertWriteEnabled(); 
      for (Adesk::UInt32 i = 0; i < mNumVerts; i++) {     
 mVerts[i].transformBy(xfm); 
 } 
 return Acad::eOk; 
 } 
  
  
 Adesk::Boolean 
 AsdkViewGeomSamp::subWorldDraw(AcGiWorldDraw* pW) 
 { 
 // Draw a pyramid. 
  
  
 // If this is the REGULAR ACAD DISPLAY mode, 
 // 
 if (pW->regenType() == kAcGiStandardDisplay) { 
  
 //  from each viewport's vantage point, figure out 
 //  which sides of the pyramid are visible, 
 //  then draw the visible ones yellow and the hidden 
 //  ones blue. 
  
 //  Set the extents of the pyramid here because 
 //  AcGiViewportGeometrys polylineEye() doesnt 
 //  set extents. 
 // 
      for (Adesk::UInt32 i = 0; i < mNumVerts; i++) {     
 AcGePoint3d pt[2]; 
 pt[0] = mVerts[i]; 
 pt[1] = mVerts[(i + 1) % mNumVerts]; 
 pW->geometry().setExtents(pt); 
 } 
 return Adesk::kFalse;  // Call viewport draws. 
 } 
  
 // Otherwise give HIDE, SHADE, RENDER, or Proxy Graphics 
 // a pyramid with filled faces. 
 // 
 const Adesk::UInt32 faceListSize = 16; 
 static Adesk::Int32 faceList[faceListSize] = { 
 3, 0, 1, 2, 
 3, 0, 2, 3, 
 3, 0, 3, 1, 
 3, 1, 2, 3 
 }; 
  
 pW->geometry().shell(mNumVerts, mVerts, faceListSize, 
 faceList); 
  
 return Adesk::kTrue;  // Do NOT CALL viewportDraw. 
 } 
  
  
 void 
 AsdkViewGeomSamp::subViewportDraw(AcGiViewportDraw* pV) 
 { 
 // For this viewport, draw a pyramid with yellow 
 // visible lines and blue hidden lines. 
  
  
 // Get this viewport's net transform.  This transform 
 // includes this entity's block transforms and this 
 // viewport's view transform; it does not include the 
 // perspective transform if we're in perspective 
 // mode -- that currently has to be applied separately 
 // when in perspective mode. 
 // 
 AcGeMatrix3d modelToEyeMat; 
 pV->viewport().getModelToEyeTransform(modelToEyeMat); 
  
 // Get the pyramid's vertices. 
 // 
 AcGePoint3d A = mVerts[0]; 
 AcGePoint3d B = mVerts[1]; 
 AcGePoint3d C = mVerts[2]; 
 AcGePoint3d D = mVerts[3]; 
  
 // Convert them to the viewport's eye coordinates. 
 // 
 A.transformBy(modelToEyeMat); 
 B.transformBy(modelToEyeMat); 
 C.transformBy(modelToEyeMat); 
 D.transformBy(modelToEyeMat); 
  
 // Save the eye coordinates. 
 // 
 AcGePoint3d AEye = A; 
 AcGePoint3d BEye = B; 
 AcGePoint3d CEye = C; 
 AcGePoint3d DEye = D; 
  
 // Perform the perspective transform if necessary. 
 // 
 if (pV->viewport().isPerspective()) { 
 pV->viewport().doPerspective(A); 
 pV->viewport().doPerspective(B); 
 pV->viewport().doPerspective(C); 
 pV->viewport().doPerspective(D); 
 } 
  
 // From that view, figure out which faces are 
 // facing the the viewport and which are not. 
 // 
 int which_faces; 
 which_faces  = ((C - A).crossProduct(B - A)).z 
 > 0.0 ? 1 : 0; 
 which_faces |= ((D - A).crossProduct(C - A)).z 
 > 0.0 ? 2 : 0; 
 which_faces |= ((B - A).crossProduct(D - A)).z 
 > 0.0 ? 4 : 0; 
 which_faces |= ((B - D).crossProduct(C - D)).z 
 > 0.0 ? 8 : 0; 
  
 // Those edges that meet between two faces that are 
 // facing away from the viewport will be hidden edges 
 // so draw them blue; otherwise, they are visible 
 // edges.  (This example is incomplete as the test is 
 // indeterminate when the face is edge-on to the 
 // screen -- neither facing away or toward the screen.) 
  
 // Draw the 6 edges connecting the vertices using eye 
 // coordinate geometry that can be back and front 
 // clipped. 
  
 AcGePoint3d verts[2]; 
 Adesk::UInt16 color; 
 // AB 
 color = which_faces & 0x5 ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = AEye; 
 verts[1] = BEye; 
 pV->geometry().polylineEye(2, verts); 
 // AC 
 color = which_faces & 0x3 ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = AEye; 
 verts[1] = CEye; 
 pV->geometry().polylineEye(2, verts); 
 // AD 
 color = which_faces & 0x6 ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = AEye; 
 verts[1] = DEye; 
 pV->geometry().polylineEye(2, verts); 
 // CD 
 color = which_faces & 0xa ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = CEye; 
 verts[1] = DEye; 
 pV->geometry().polylineEye(2, verts); 
 // DB 
 color = which_faces & 0xc ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = DEye; 
 verts[1] = BEye; 
 pV->geometry().polylineEye(2, verts); 
 // BC 
 color = which_faces & 0x9 ? kYellow : kBlue; 
 pV->subEntityTraits().setColor(color); 
 verts[0] = BEye; 
 verts[1] = CEye; 
 pV->geometry().polylineEye(2, verts);