= Available
electronically. I am in the process of reentering old ones. See All.
NYIT Favorites 1975-1979
New York Institute of Technology
= Available
electronically. I am in the process of reentering old ones. See All.
*The last two were written while I was at JPL on work done at NYIT.
Paint, Tech Memo
7, 20 Jul 1978
INTRODUCTION. Paint is a menu-driven computer program for handpainting two-dimensional images in full color. It is a highly interactive software package with which a human artist may employ the power of a digital computer to compose paintings which are entirely of his own creation. The “canvas” is actually a large piece of digital computer memory which is displayed for the artist on a conventional color television monitor. His “brush” is an electronic stylus resembling an ordinary pen. Its shape can be any two-dimensional shape he desires, so long as it fits into the canvas memory space. He may choose any color he desires from a “palette” of 256 colors. If this is an inadequate selection, he may mix his own set of colors from a vast set of possibilities. The main purpose of this paper is to describe in detail how an artist accomplishes these acts and what his choices are.
A secondary purpose is a careful description of a successful human engineering design. Paint is designed to have a “natural feel” and to be readily usable by computer-naďve people. There are detailed descriptions of the techniques which make this possible. In fact, this paper is designed to be read as a textbook for Paint users.
Paint includes routines for defining and selecting brushes, automatic filling and clearing large areas, saving and restoring pictures, magnifying the canvas temporarily for detail work, and recording histories of picture composition. These functions will be described fully. Subsidiary routines available to the artist include such graphic aids as straight-line, ellipse, circle, and spline generators, mirroring, rotation, etc. These programs will not be described here nor will be the large overseeing program Bigpaint of which Paint is a principal component. Bigpaint permits the artist to work on a canvas so large that it cannot all be displayed simultaneously.
There have been several versions of Paint at NYIT (New York Institute of Technology). Each version exists or existed for a specific configuration of equipment. Appendix A gives the various configurations that have been tried, with appraisals of each.
One version of Paint represents increased sophistication rather than mere equipment reconfiguration. This is called Paint3. It is superior to Paint described here in its use of 24 bits for representation of each point in the canvas memory rather than 8 bits. Appendix B explains the extension of Paint to Paint3.
Appendix C gives a brief history of painting programs, emphasizing those which most directly influenced Paint.
[This is the original Paint paper with original illustrations. The two published versions have been edited slightly from it. This paper figured highly in two patent trials.]
, With Addendum of 21 Aug 1979, Tech Memo 10, 27 Jul 1979
INTRODUCTION. Texas - from TEXture Applying System - is a set of programs for moving pictures about in 3-space to obtain other pictures. Texas makes pictures comprised of other pictures embedded in 3-space. Here a picture, or texture, may be thought of as the contents of a framebuffer, although it may be stored temporarily in a disk file or disguised as a mipmap. Texas takes as input a stageset, which is a set of flats, where a flat is a picture painted (mapped) onto the surface enclosed by a planar, convex quadrilateral. Its output is a 2-dimensional rendering of a stageset as viewed from some vantage point in 3-space.
Texas features incremental rendering of textures in perspective, depth darkening, front and back textures for each flat, z buffering or priority sorting for hidden surface removal, antialiasing of edges or tag buffering for ex post facto dekinking. It uses the Picture System II driver by Jim Clark, the mipmap utilities of Lance Williams and Dick Lundin, and has an interface to Garland Stern’s 3-dimensional animation program Arbor (or Boop) and to Ed Catmull’s polygon rendering program Render.
Texas is intended to be a generalization of the multiplane camera. The current version lacks transparency [but see Appendix], however, so cannot yet do multiplaning. Another inadequacy at present is the priority sort algorithm which is simple minded. Intended additions are light sources, shadows, global partial transparencies for individual flats, correct pixel preimage averaging, as well as local transparency and a better sort.
, 6 Aug 1979
INTRODUCTION. One of the most basic picture-making tools in computer graphics (specifically, color raster graphics) is moving or copying an image from one location to another, from one type of memory device to another type. What we shall call painting is an example of this basic operation. One image, called the brush, is copied from disk memory into main and then repeatedly copied from there into a special type of visible memory called a framebuffer at a changing position determined by the user’s hand on a tablet. All the variations on simple copying available on a computer are, of course, available for the special case of painting. We shall detail several of these.
[This paper figured highly in two patent trials because it contains an early description of matting.]
ABSTRACT. Table look-up procedures are particularly useful at computer graphics installations because of the large chunks of cheap random access memory (framebuffers) which tend to be components of these facilities. We explain here how one additional framebuffer and one analog control device in addition to the tablet create a powerful and flexible extension to any typical framebuffer painting program. In particular, this readily available extra equipment gives the artist brushes which change size, shape, orientation, and/or color in realtime and smoothly. Examples are rotating brushes, animated brushes, airbrushes with changing spread and density, oriented brushes which track the direction of motion, and many more. That is, the artist is given a third dimension of stylus control which may be as graceful as the spatial two. He may define this new dimension from a menu of selections. The extra framebuffer is used as table memory. The extra device (e.g., joystick, trackball, pot, footpedal, microphone, strain guage, keyboard) is used as a controller for the added dimension. Realtime is obtained by using the output of the controller for table look-up.
Incremental Rendering of Textures in Perspective
, 28 Oct 1979
ABSTRACT. An incremental, scanline-ordered algorithm for rendering a 2-dimensional texture into a planar convex polygon embedded in 3-space is presented. The textured polygon is projected into a viewing plane where it is seen in perspective. The method is shown to cost a divide and two lerps per pixel more than the well-known incremental algorithm for rendering an orthographic view of a texture or a perspective view of a "texture" consisting of a single color (lerp = linear interpolation). It is argued that the divide is necessary - that, for example, second-order incrementing is not good enough in general.