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# RAYTRACING YOUR CREATION

Once you have finished creating all your solids, positioned them in their correct relationships to each other, formed all your regions (forming your finished object), created groups (if required), you can now do a ray- tracing of the view displayed on the screen.

Note! If you want to display solids or objects (collection of solids regioned together) of different colors, each of the solids or objects must be separate regions so you can give them a specific color.

The raytracing command is rt [-s#]

This command produces a color shaded image of the solids or objects on the display. This color shaded image will appear on a frame buffer display. The resolution of the image (number of rays) is equal to "#" from the "-s" option. If the "-s" option is absent, 50x50 ray solution will be used (very course raytrace). The higher the "-s" option the better the raytracing, but it takes longer to display. Recommended optimun value of "-s" option for picture quality and speed of display is 256!. Some examples follow:

rt -s128
rt
rt -s256

When the rt command is given the text and graphic window will appear, then the frame buffer starts to appear (the picture window). The first scaned display will be what was previously stored in it, it will then over write it with your picture; sometimes two buffer scans are displayed before yours.

The default background color is blue with steel grey colored solids and objects. The terminal will beep when the scanned picture is finished; press return to get back to the "text and graphic" window.

With the blue background it is sometimes hard to visualize the raytraced picture; two things you can do to improve the situation is: (a) Make separate regions for all solids and objects, so that you can assign a specific color to each region; this can be a time consuming task if you have a lot of solids and objects. (b) Construct as a separate region, three thin flat plates to form two walls with a bottom, as shown below; using "make name arb8", then solid editing this arb8, using move faces to the required thickness, then use command "cp" (copy command) to make two more copies which you can rotate to their respective relationships, then translate all three into the correct positions relative to each other and the solids and objects you are displaying.

The advantage of doing this is to give the light source something to reflect off, giving back lighting; improving contrast considerably. With the three plates formed into their own region you can delete them from the screen with the "d" command, rotate your creation then re-display your plates (walls) with the "e" command to do another rt, the walls need to be deleted from the display when you rotate your objects, otherwise everything will rotate together.

A bonus of having constructed these three walls is that you can quickly change the material type to "mirror" so that you can get reflections of the three hidden faces.

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