Siggraph 1996 stands out in my memory as one that influenced my research and interests greatly. Without further ado, here's my picks.
Modeling and Rendering Architecture from Photographs: A hybrid geometry- and image-based approach, Paul E. Debevec, Camillo J.Taylor, Jitendra Malik, pp. 11-20. This was the first public showing of Facade, one of the earliest announced modeling from photogrammetry applications. Prior to this, software such as Alias Sketch had plane perspective matching, but very little software did more than that.
The Lumigraph, Steven J. Gortler, Radek Grzeszczuk, Richard Szeliski, Michael F. Cohen, pp. 43-50. The Lumigraph captured geometry and plenoptic flow of light at every 3d spatial position (x,y,z) for every 2d direction (theta, phi). This seminal paper unearthed a rich research vein.
The Feudal Priority Algorithm on Hidden-Surface Removal, Han-Ming Chen, Wen-Teng Wang, pp. 55-64. This is an interesting approach to viewpoint dependent polygon ordering, and offers an alternative to the BSP using less splits. I haven't seen it used in practice, but it seems to have potential.
Hierarchical Image Caching for Accelerated Walkthroughs of Complex Environments, Jonathan Shade, Dani Lischinski, David. H. Salesin, Tony DeRose, John Snyder, pp. 75-82. One of the original papers on using imposters to sit in for portions of geometry to accelerate rendering. Portions of geometry are rendered off onto cards, and when measure distortion due to camera motion exceeds a threshold, the imposter is re-cached. The project page with source to run on an SGI Indigo is here.
Linear-Time Dynamics using Lagrange Multipliers, David Baraff, pp. 137-146. Baraff got a whole generation of physics programmers kick-started with this paper. A loop free articulated figure is decomposed into a set of constraints that can be evolved with Lagrange multipliers in an Order(n) algorithm that first solves all the forward constraints, and then all the backward constraints. The approach is based on the observation that any pairwise acyclic set of constraints can be solved in linear time using sparse-matrices.
Limit Cycle Control And Its Application to the Animation of Balancing and Walking, Joseph Laszlo, Michiel van de Panne, and Eugene Fiume, pp. 155-162. Periodic motions can be described as a closed limit cycle. The limit cycle, such as the motion of a joint during walking, might be inherently unstable, but feedback is provided to force the dynamic system back to the cycle. In toys, this might be accomplished by physical damping; in a simulation it can be accomplished through the application of forces. Results are presented for a human type rig, and an AT-ST.
Sketch: An Interface for Sketching 3d Scenes, Robert C. Zeleznik, Kenneth P. Herndon, and John F. Hughes, pp. 163-170. A series of two dimensional mouse gestures are presented which yield 3d constructions. For example, two parallel lines with a small circle at the bottom is interpreted as a cylinder. The gestures can also be used to manipulate scene elements. These methods seem intuitive, and elements of them can be seen in modern applications such as Sketchup and Blender.
OBBTree: A Hierarchical Structure for Rapid Interference Detection, Stefan Gottschalk, Ming C. Lin, Dinesh Manocha, pp. 171-180. A foundational paper on hierarchical data structures. Hierarchies of oriented bounding boxes enclose objects with arbitrary fidelity.
Disney's Aladdin: First Steps Toward Storytelling in Virtual Reality, Randy Pausch, Jon Snoddy, Robert Taylor, Scott Watson, Eric Haseltine, pp. 193-203. The focus of the work was the immersive aspects of the VR environment. This work is one of the earliest demonstrations of compelling 3d cartoon characters integrated into an interactive 3d environment. BTW, Randy Pausch's last lecture is a must view.
The Virtual Cinematographer: A Paradigm for Automatic Real-Time Camera Control and Directing, Li-wei He, Michael F. Cohen, David H. Salesin, pp. 217-224. Another foundational paper on digital cinematography. Lines of action and so on are encoded as a set of rules for a state machine. In more recent work this sort of thing is accomplished by optimal control algorithms, however this paper contains many useful insights.
Comic Chat, David Kurlander, Tim Skelly, David H. Salesin, pp. 225-236. I'm surprised this paper hasn't seen more attention. It breaks down conversations into a presentation form resembling comic books; the output looks quite fun. Incidentally, Tim Skelly has designed some of my favorite arcade games. The Comic Chat project page is here. Apparently the chat program used to exist embedded in Internet Explorer, but the server is now down.
A Model of Visual Adaptation for Realistic Image Synthesis, James A. Ferwerda. Sumanta N. Pattanaik. Peter Shirley. Donald P. Greenberg, pp. 249-258. This paper develops a computational model of visual adaptation capturing threshold visibility, color appearance, visual acuity, and adaptation over time. Now that HDR has come into its own, these observations should be particularly useful as we develop new tone mapping paradigms.
Blue Screen Matting, Alvy Ray Smith, James F. Blinn, pp. 259-268. Published on the expiry of the fundamental Vlahos patents, the mathematics of blue screen matting are explored; constant color matting is shown to be mathematically intractable, and a two-constant backing color method is shown to be solvable. This method requires two exposures, but I am wondering if the technique could be used in a single exposure (with two sensors) if one of the backgrounds was illuminated in an invisible wavelength?
A Cellular Texture Basis Function, Steven Worley, pp. 291-294. A foundational paper in texture synthesis; Worley created a new noise basis function that works by partitioning space into a random array of cells.
Visual Models of Plants Interacting with Their Environment, Radomır Mech and Przemyslaw Prusinkiewicz, pp. 397-410. L-Systems are extended to allow interaction with the environment. Plant growth can be modified by competition for space, access to light, water, or nutrients, wind, and so on.
Flow and Changes in Appearance, Julie Dorsey, Hans Kohling Pedersen, Pat Hanrahan, pp. 411-420. Particles are simulated over surfaces, and according to material properies, material is absorbed or deposited into the surfaces, thus changing the appearance of the object.
Image-Guided Streamline Placement, Greg Turk, David Banks, pp. 453-460. A very exciting method of generating coherent streamlines using what is effectively a cell or particle based method. This method should generalize readily to GPU. The project page, including source code for an implementation is here.