Awesome blog post on the VFX in 2001 a Space Odyssey. Great read.
Doug Trumbull: "Filming of the 'Dawn of Man' sequence took place entirely on only one stage at the studio. Distant backgrounds for all the action were front-projected eight-by-ten Ektachrome transparencies, using probably the largest front-projection device ever made, and constructed specially for 2001 by Tom Howard. The projector consisted of a specially intensified arc source with water-cooled jaws to hold the oversized carbons, special heat-absorbing glass, giant condensing lenses which would occasionally shatter under the intense heat, special eight-by-ten glass plate holders and positioning mounts, an extremely delicate semi-silvered mirror, and a specially built nodal point head so that the camera could pan, tilt, and zoom without fringing of the image."