Making a Ray Traced Picture

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A ray tracing is made using one of the picture items in the Ray Trace submenu of the Graphics menu, in the New Picture and In New Window submenus of the ray tracing window context menu, or the corresponding toolbar button: Color  makes a standard picture showing shaded cells. Color+Etch  draws etch lines on top of the color picture in a single ray tracing. Etch Over  draws etch lines on top of the existing image. Clear+Etch erases the ray tracing window before making an etch image. Clear  erases the window.

The view point and orientation of the picture matches the projection in the dynamic 3D window. The image is not an exact copy because of differences in the distance to the viewpoint. The Ray Trace Options property page contains a factor that multiplies the distance to the view point. A large factor is similar to the OpenGL orthographic projection, while a small distance results in a perspective view. The initial scaling is set so that the entire model bounding box is visible. The options page contains a multiplier for the bounding box size when used in the scaling calculation.

The picture can be scaled with the zoom in  and zoom out  toolbar buttons, with items in the Zoom subsubmenu of the Ray Trace submenu of the Graphics menu, and with items in the Zoom and Zoom to New Window submenus of the ray tracing window context menu. An interactive zoom box is drawn with the left mouse button and shift key held down. A new picture is drawn following any of these actions in the same style (Color, Color+Etch, ...) as the previous picture.

In pictures where a semitransparent cell is visible, Color+Etch may give spurious lines. The desired image can then be achieved by a Color picture followed by Etch Over. Semitransparent cells are treated as opaque in Etch Over and Clear+Etch. Before each ray tracing, the orientation is taken from the OpenGL plot unless Lock View Point is checked in the ray tracing context menu. If that image is rotated between the Color and Etch Over plots, the etch lines will not be aligned with the color image.

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