   transforming nearplane
  Hello,I need your help solving this problem. There is a color coded cube withminimum coordinate (0,0,0) and maximum coordinate (1,1,1). Each vertex ofthis cube has the respecitve color. That means, Vertex 0,0,0 is coloredwith 0,0,0, vertex 1,0,0 is colored with 1,0,0. Please have a look at the link http://img80.imageshack.us/i/nearplane.jpg/The top image shows such a color coded cube. The problem is, when moving the camera into the cube, there are no colors where the nearplane clips the cube(bottom image). To solve this problem i calculate the near plane vectors and multiply them bythe inverse modelview matrix.In eyespace the camera is at 0,0,0. The tangent is  tan(fovY/2) = (height/2) / nearplane_distance).So the height/2 is tan(fovY/2) * nearplane_distancefloat fovy_half = deg_to_rad * fovYgrad * 0.5f;float near_height_half = tan(fovy_half) * nearplane_dist;float near_width_half = near_height_half * (aspect_ratio);Vector4<float> nbl(-near_width_half, -near_height_half, -nearplane_dist, 1.0f)Vector4<float> nbr( near_width_half, -near_height_half, -nearplane_dist, 1.0f)Vector4<float> ntl( near_width_half,  near_height_half, -nearplane_dist, 1.0f)Vector4<float> ntr(-near_width_half,  near_height_half, -nearplane_dist, 1.0f)Matrix4<float> modelview;glGetFloatv(GL_MODELVIEW_MATRIX, modelview.get());Matrix4<float> mvi = Matrix4<float>::transpose(Matrix4<float>::inverse(modelview));nbl = mvi * nbl;nbr = mvi * nbr;ntl = mvi * ntl;ntr = mvi * ntr;The nearplane vector are now in objectspace coordinates. With these 4 vectorsI draw a fullscreen quad. Because the cube is from 0,0,0 to 1,1,1 and the colors as well, the 4 vectors nbl,nbr,ntl,ntr are use to represent the colorsof the near plane. The goal is to fill the clipped area with the colors. Well, there is a colored "nearplane", but the colors are not correct.glMatrixMode(GL_MODELVIEW); glPushMatrix(); glLoadIdentity(); glMatrixMode(GL_PROJECTION);glPushMatrix(); glLoadIdentity ();glBegin(GL_QUADS); glColor3d(nbl.x, nbl.y, nbl.z); glVertex3f(-1.0f, -1.0f, -0.50f); glColor3d(nbr.x, nbr.y, nbr.z); glVertex3f( 1.0f, -1.0f, -0.50f); glColor3d(ntr.x, ntr.y, ntr.z); glVertex3f( 1.0f,  1.0f, -0.50f);glColor3d(ntl.x, ntl.y, ntl.z); glVertex3f(-1.0f,  1.0f, -0.50f); glEnd ();glPopMatrix(); glMatrixMode(GL_MODELVIEW); glPopMatrix ();I hope someone can help me, solving this problemregards,c-mos[Edited by - c-mos on April 23, 2010 7:02:13 AM]