Thanks Pete.A great explanation. That conforts me in saying that clouds are very subtil VFR navigation aids.Cheers,Cedric

><>>>Can you explain 3D textures? Do you mean ones that require>stereo glasses?Mike,You can start here:http://www.ati.com/developer/shaderx/ShaderX_3DTextures.pdfhttp://www.opengl.org/resources/tutorials/...tes/node36.htmlhttp://gpwiki.org/index.php/OpenGL_3D_TexturesCheers,Jason