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A small VRML viewer using OpenGL and MFCBy Pierre Alliez |
VC6, OpenGL, Dev
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FIG. 1. You can easily display a wrl-based terrain
using OpenGL and MFC.
This contribution is a small MFC sample to learn how to :
int list = ::glGenLists(1); // ask for a free id number ::glNewList(list,GL_COMPILE_AND_EXECUTE); ::glBegin(GL_TRIANGLES); // std gl calls here... fill vertices, normals, colors ::glEnd(); ::glEndList();A good command sequence to use a display list may be :
if(::glIsList(list) == GL_TRUE)
::glCallList(m_ListOpenGL);
The sample builds a scene graph from a vrml 2.0 file (exported via 3D Studio
Max only), then uses display lists. Each 3D mesh contains a list number,
and use a glCallList command instead of standards glBegin(GL_TRIANGLES)
commands when its list is built. A flag m_Modified permits to rebuild the
list when the mesh is modified.
//******************************************** // The 3D mesh class definition //******************************************** class CMesh2d : public CObject3d { private : // Std datas CArray<CVertex3d> m_ArrayVertex; CArray<CFace3d> m_ArrayFace; // OpenGL-specific unsigned int m_ListOpenGL; BOOL m_ListDone; BOOL m_Modified; .../... public : BOOL glDraw(); .../... } //******************************************** // Mesh drawing //******************************************** BOOL CMesh2d::glDraw() { // Build list at first if(!m_ListDone || m_Modified) glBuildList(); // Is the list valid ? if(::glIsList(m_ListOpenGL)==GL_TRUE) { ::glCallList(m_ListOpenGL); return TRUE; } return FALSE; }
//*********************************************** // RenderScene //*********************************************** void CMeshDoc::RenderScene() { // Main drawing m_SceneGraph.glDraw(); // Add wireframe (no light, and line mode) if(m_AddWireframe) { // Set state ::glDisable(GL_LIGHTING); ::glPolygonMode(GL_FRONT_AND_BACK,GL_LINE); ::glEnable(GL_POLYGON_OFFSET_LINE); ::glPolygonOffset(m_PolygonOffset,-1.0f); // Draw again... m_SceneGraph.glDraw(TYPE_MESh2D); // Restore light and mode ::glDisable(GL_POLYGON_OFFSET_LINE); ::glPolygonMode(GL_FRONT_AND_BACK,GL_FILL); ::glEnable(GL_LIGHTING); } ::glFlush(); }
FIG.3. The one-to-four triangle subdivision scheme used by method."wrl_viewer/wrl_viewer3.jpg" height=191 width=600>
//*********************************************** // Smooth subdivision //*********************************************** void CMeshDoc::OnMeshLoop() { BeginWaitCursor(); int NbObject = m_SceneGraph.NbObject(); for(int i=0;i<NbObject;i++) { CObject3d *pObject3d = m_SceneGraph[i]; if(pObject3d->GetType() == TYPE_MESh2D) { CMesh2d *pMesh = (CMesh2d *)pObject3d; pMesh->SubdivisionLoop(); } } UpdateAllViews(NULL); EndWaitCursor(); }
FIG.5. See the visual enhancement obtained by a smooth
subdivsion scheme..
//*********************************************** // Left button -> x/y translation //*********************************************** void CMeshView::OnLButtonDown(UINT nFlags, CPoint point) { m_LeftButtonDown = TRUE; m_LeftDownPos = point; SetCapture(); CView::OnLButtonDown(nFlags, point); } void CMeshView::OnLButtonUp(UINT nFlags, CPoint point) { m_RightButtonDown = FALSE; m_LeftButtonDown = FALSE; ReleaseCapture(); CView::OnLButtonUp(nFlags, point); } //*********************************************** // Right button : z translation //*********************************************** void CMeshView::OnRButtonDown(UINT nFlags, CPoint point) { m_RightButtonDown = TRUE; m_RightDownPos = point; SetCapture(); CView::OnRButtonDown(nFlags, point); } void CMeshView::OnRButtonUp(UINT nFlags, CPoint point) { m_RightButtonDown = FALSE; m_LeftButtonDown = FALSE; ReleaseCapture(); CView::OnRButtonUp(nFlags, point); } //*********************************************** // Mouse move // Both : rotation // Left : x / y translation // Right : z translation //*********************************************** void CMeshView::OnMouseMove(UINT nFlags, CPoint point) { // Both : rotation if(m_LeftButtonDown && m_RightButtonDown) { if(m_xyRotation) { m_yRotation -= (float)(m_LeftDownPos.x - point.x) * m_SpeedRotation; m_xRotation -= (float)(m_LeftDownPos.y - point.y) * m_SpeedRotation; } else { m_zRotation -= (float)(m_LeftDownPos.x - point.x) * m_SpeedRotation; m_xRotation -= (float)(m_LeftDownPos.y - point.y) * m_SpeedRotation; } m_LeftDownPos = point; m_RightDownPos = point; InvalidateRect(NULL,FALSE); } else // Left : x / y translation if(m_LeftButtonDown) { m_xTranslation -= (float)(m_LeftDownPos.x - point.x) * m_SpeedTranslation; m_yTranslation += (float)(m_LeftDownPos.y - point.y) * m_SpeedTranslation; m_LeftDownPos = point; InvalidateRect(NULL,FALSE); } else // Right : z translation if(m_RightButtonDown) { m_zTranslation += (float)(m_RightDownPos.y - point.y) * m_SpeedTranslation; m_RightDownPos = point; InvalidateRect(NULL,FALSE); } CView::OnMouseMove(nFlags, point); }
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Last Updated: 30 Nov 1999 Editor: Chris Maunder |
Copyright 1999 by Pierre Alliez Everything else Copyright © CodeProject, 1999-2009 Web16 | Advertise on the Code Project |
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