View > 3D View Options > 3D Projection Settings
Press the More Sun... button. That should show you the dialog below. Play with the settings. For a 'clean' OpenGL look, I've stuck to white sun and white ambient colours. The more ambient, the brighter the image, though it leads to over saturation, in my opinion.
Also check the sun altitude. For nice shadows set it to something between 45-55 degrees. Try matching the azimuth of sun to azimuth of camera, or something in 45 degree steps if you have a mostly orthogonal model.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
Windows 10 Pro
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