58 lines
2.9 KiB
Plaintext
58 lines
2.9 KiB
Plaintext
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ABOUT THIS PROGRAM:
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Backtrace is an OpenGL program meant to simulate ray tracing.
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It displays a refractive sphere above a plane. The sphere is lit by
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red, green, and blue spotlights which may be manually moved. The
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shadow of the sphere and the light which is refracted through the
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sphere are projected onto the plane.
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The "Material" menu controls the refractiveness of the sphere.
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The "Draw" menu controls which subparts of the scene are
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drawn. By default, the "Draw Texture" option is off. Texture mapping
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is slow on many systems and the texture map is completely gratuitous.
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However, you may want to turn texture mapping on once to see if the
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performance is acceptable on your system.
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The "Subdivision" menu controls the number of subdivisions
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used to draw the plane, the sphere, the lights, the shadows, and the
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refractions. More subdivisions will look better, but will be slower.
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The "Lights" menu can be used to turn the lights on and off on
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an individual basis. The "Reset Lights" button moves all the lights
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back to their original positions.
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The "Quick Motion" option under the option menu makes motions
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in r and phi (controlled by the middle and right mouse buttons,
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respectively) happen much more quickly by delaying recompuation of the
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shadows and refraction until the mouse button is released. The
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"Rotate Automatically" toggle causes the lights to rotate about the z
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axis at random speeds.
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Moving of the lights is accomplished with the mouse. The
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author wishes to apologize for the horribly awkward interface. To
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move a light, move the pointer over it and press one of the mouse
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buttons down. Draw the mouse to move the light. It is easiest to
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imagine the lights in spherical coordinates. The left mouse button
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controls rotation in theta (about the z axis). Moving the mouse
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horizontally while holding down the left mouse button will increase or
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decrease theta.
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The middle mouse button controls the radius, or the distance
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of the light from the sphere. Dragging the mouse toward the center of
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the screen decreases the distance of the light from the sphere, while
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moving away from the center of the screen increases the distance.
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The right mouse button controls rotation in phi, which can be
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thought of as the elevation of the light. Moving the mouse
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horizontally will change the elevation.
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TO COMPILE:
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Type "make." Note that you must have a C++ compiler
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installed. There may be a warning or two, but these should not cause
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problems. You must first have compiled libtk.a. You must also have
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a development copy of Motif and the Motif GL widget installed.
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OTHER MAKEFILE TARGETS:
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"make clean" removes objects, ~ files, and core files.
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"make clobber" also removes the executable.
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KNOWN BUGS:
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It's possible to change the phi of a light in such a way that
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the light gets below the sphere, which leads to unexpected (and
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inaccurate) results.
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AUTHOR:
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Celeste Fowler
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