VectorDraw Developer Framework(VDF)是一個用於應用程序可視化的圖形引擎庫。有了VDF提供的功能,您可以輕鬆地創建、編輯、管理、輸出、輸入和打印2D和3D圖形文件。
問:
如何在3D視圖中檢查對象是否隱藏在另一個對象中?例如,我有兩個多面體,一個是z = 100的大面積,另一個是z = 0的面,並且視圖是隻有一個多面體是可見的,另一個多面體是在大面體後面,並且是完全看不見的在屏幕上。
答:
你需要一些OpenGL代碼來檢查一個對象是否落後於另一個對象(不可見)。
您需要的代碼如下:
vdPolyface purple; // this is the polyface to check if is behind the green polyface void test() { // just create the objects vdPolyface pf1 = new vdPolyface(doc); pf1.CreateBox(new gPoint(0, 0), 1, 1, 1, 0); pf1.PenColor = new vdColor(Color.Purple); doc.Model.Entities.AddItem(pf1); purple = pf1; // this is the polyface to check if is behind the green polyface vdPolyface pf2 = new vdPolyface(doc); pf2.CreateBox(new gPoint(-2, 2), 4, 4, 4, 0); pf2.PenColor = new vdColor(Color.Green); doc.Model.Entities.AddItem(pf2); // this is the green polyface that hides the purple one doc.RenderMode = vdRender.Mode.Shade; //doc.CommandAction.View3D("VINW"); doc.CommandAction.View3D("VINE"); } bool IsObjectVisible = false; void test1() // this is the method that checks the “visibility” using the OnDrawAfter event { IsObjectVisible = false; doc.OnDrawAfter += new vdDocument.DrawAfterEventHandler(TestObjectVisibility_OnDrawAfter); doc.RenderMode = vdRender.Mode.Shade; doc.Redraw(true); doc.OnDrawAfter -= new vdDocument.DrawAfterEventHandler(TestObjectVisibility_OnDrawAfter); MessageBox.Show(IsObjectVisible ? "Object is visible" : "Object is not visible"); } void TestObjectVisibility_OnDrawAfter(object sender, vdRender render) { double[] _modelMatrix = new double[16], _projMatrix = new double[16]; int[] _viewport = new int[4]; double pwinx = 0.0, pwiny = 0.0, pwinz = 0.0; //GET the active world to view and view to pixel matrixes VectorDraw.Render.OpenGL.OpenGLImports.glGetDoublev(VectorDraw.Render.OpenGL.OpenGLImports.Parameters.GL_PROJECTION_MATRIX, _projMatrix); VectorDraw.Render.OpenGL.OpenGLImports.glGetDoublev(VectorDraw.Render.OpenGL.OpenGLImports.Parameters.GL_MODELVIEW_MATRIX, _modelMatrix); VectorDraw.Render.OpenGL.OpenGLImports.glGetIntegerv(VectorDraw.Render.OpenGL.OpenGLImports.Parameters.GL_VIEWPORT, _viewport); Rectangle winrc = new Rectangle(_viewport[0], _viewport[1], _viewport[2], _viewport[3]); foreach (gPoint pt in purple.VertexList) { VectorDraw.Render.OpenGL.OpenGLImports.gluProject(pt.x, pt.y, pt.z, _modelMatrix, _projMatrix, _viewport, ref pwinx, ref pwiny, ref pwinz); Point winPt = new Point((int)pwinx, (int)pwiny); if (!winrc.Contains(winPt)) continue; //Get the existing depth in previous calculated pixel double depth = VectorDraw.Render.OpenGL.OpenGLImports.glReadPixelDepth((int)(pwinx), (int)(pwiny)); //the pt is visible if the pwinz is smaller than the existing(it is closest to eye) double def = pwinz - depth; if (def <= 0.000001) { IsObjectVisible = true; break; } } }