Issues of Perspective



Constructing solids in perspective is an exercise in judgement. Although I discussed Doblin's system of two-point perspective with its measuring points and the ability to lay out an indexed grid, the system represents an approximation of reality.

The first issue to cover is the nature of drawing in perspective which, in many ways, is the most complicated aspect to understand. In reality, perspective seems obvious and without distortion because we observe space in three dimensions (horizontal, vertical, and depth or, in mathematical terms, the x, y, and z axes). Translating this phenomenon to two dimensions requires a graphic understanding of the shape of objects in space and the related visual changes as space recedes in distance.



Fig.01 - Doblin, J. (1956), p.8 - A view of the picture plane

 The Picture Plane is the surface of a plane on which all 3-dimensional objects we view beyond are represented 2-dimensionally. The Picture Plane is usually represented by the pad of paper (or computer screen) on which we depict the objects. See Fig.01 for Doblin's illustration. Please note that his drawn visualization of the observer ( geometrically pear-shaped with a bow-tie and pointed shape for a head), as distracting as it may be, is purely for understanding the context.

The nature of our vision is 3-dimensional, however, so, unless the picture plane is infinitely large to depict all space in our front view to the periphery, we restrict our recorded view to an area known as the Cone-of-Vision. This idea is best represented by the analogy of a camera lens: the camera can only see to a certain angle away from the center of vision.

If one sets up a two-point perspective drawing it becomes apparent that a square grid on the ground plane changes shape depending both on the distance from the viewer and on the proximity to the outer boundaries of the cone-of-vision.


Fig.02 - Doblin, J. (1956), p.18 - The 'Cone of Vision' - Note the distortion near to and beyond the boundaries.

 In Figure 02, note the distortion in the shape of a square footprint near and beyond the boundary of the Cone of Vision. According the to the perspective grid, the shape of a square would have angles less than 90 degrees, an impossibility. This phenomenon may often be observed in architectural photography where images are distorted due to the prismatic nature of the wide-angle lenses used on the camera. For industrial design, however, drawings of form would confuse the observer if distortion was included in the visualization. In Fig. 2, squares A1 and B appear to be in proportional perspective. This area could be termed a 'sweet spot' for accurate visualization. Moving away from this area uses perspective grids that become progressively distorted.


Fig. 03 - 30-60 two-point perspective. Note the difficulty in matching a template ellipse for the cone base while maintaining a vertical minor axis.


 In Figure 03, the 'sweet spot' for accurate perspective is near the picture plane and origin, the cube shows the least distortion. Moving away to the left, however, one notices that the ellipses used in the cone and cylinder do not coincide completely with the foot prints of the outline parameter cubes. With all vertical center lines and surfaces kept perpendicular to the ground plane, ellipse guides (true perspective with no distortion) become unreliable and don't fit the square footprints.
Observing the same view in Maya, however, the software has the sophisticated ability to adjust both ellipses and vertical lines to a 3rd vanishing point (Fig.04).


Fig.04 - Screenshot of four solids in Maya. Note the 3rd point perspective for vertical lines.



If one introduces a third-point in the drawn perspective the template ellipses work much better (Fig.05) The implications are, however, that a 3-point perspective system must be used to depict larger visualizations to avoid distortion.


Fig. 05 - 3-point perspective shows deviation of vertical lines from y-axis


Interestingly, one can document the mathematical precision of the Maya visualization software by observing the change in perspective comparing an ellipse on the screen and an ellipse from a template. As any particular point in space recedes into the distance, the angle of view changes incrementally. Ellipse templates only give an approximation every 5 degrees and are symmetrical front to back. Maya, conversely, is able to accurately predict the exact elliptical angle at any point in space - thus, the deviation shown from matching the front half of a template to the screen image to the back half in Figure 06.


Fig. 06 - Comparison of ellipse template and Maya-generated ellipse. Note the gap at the rear/top of the two ellipse representations.

 As capable as Maya is at depicting many variations of perspective there lie hidden traps for the less-than-expert user. If one selects the Camera icon from the sub-menu, a host of variables are offered for adjustment: Angle of View, Focal Length, Camera Aperture, Film Aspect Ratio, and Camera Scale are among several that may be fine-tuned. Note the differences between the perspective views of Figures 07 and 08 which result mostly from changes in just the aperture.


Fig. 07 - Super 16mm - note the foreshortening in the foreground.



Fig.08 - 70 mm Projection - note the wide-angle distortion in the perspective

As shown in figures 07 and 08, the impact of a single image can change dramatically with just a few adjustments to the software viewing set-up. This represents a risk for the designer who may not fully understand the implications of the power of modeling/rendering software.

Although dramatic, the implications of forced perspective shown in figure 08 can be illustrated another way. Doblin explains that the angle of a horizontal square intersection visualized in a 2-dimensional plane can never be 90 degrees because it would require the viewer to be looking down from directly above plane or object. See figure 09. In design, one has to balance inspiring the client and risking confusion from images that don't represent reality.


Figure 09 - Doblin, J. (1956), p. 19. What distorted perspective means to the viewer.



Getting Started - Cognition Issues

In design education, as most disciplines, the challenge is often not the end result but the learning process involved in gaining knowledge considered arcane but essential to developing a system for creativity.


Learning to draw is arguably the single most difficult skill designers must master. Sometimes referred to as the 'language of design', drawing is how designers communicate to the client, to other designers, and to themselves in the process of problem solving, creation, and refinement. To properly visualize a concept, perspective drawing skills are necessary to translate an idea in the mind to a two dimensional image that "looks right".


In 1956, Jay Doblin published a treatise on design perspective systems focusing on product visualization. His two-point 30-60 degree layout shown below in print (Fig.1) and in example (fig.2) may require a large flat surface (e.g., drafting table) to properly complete. Although considered obsolete, this system helps the designer understand the structure of vanishing points and perspective - located off the page for the observer but very much considered by the designer in the visualization process. The advantage of this system is that the designer understands the logic of perspective systems and automatically creates a grid for repeated use.



Fig.1 - Doblin, J., 1956. Perspective - a new system for designers. p.24

 

Doblin's perspective system allows the designer to construct an indexed grid for any unit of measurement to draw an accurate, dimensional, 2D representation of a concept.



Fig.2 - Cube in perspective.

 
Others have developed instructional systems using established perspective grids that may be used as underlays in the drawing process (Fig.3). Dr. Noel Mayo, at the Ohio State University, has used this system successfully not just in professional practice but also in helping students overcome the fear associated with most drawing exercises.





Fig.3 - Mayo, N. and Feracho, T., 2002.

  

The difficulty of learning perspective drawing is that little of the process is intuitive. Additionally, the designer must acquire the skill to evaluate whether the drawing "looks right" since all perspective systems have some distortion built in as approximations of reality. Professional designers are required to present images that look real - if the perspective is incorrect, the observer or client may misinterpret the concept.

Conversely, learning 3D computer visualization software is neither intuitive nor simple. The digital modeling and rendering systems are both extraordinarily capable and complex at the same time. They offer tools to visualize forms and images in a myriad of variations while preparing electronic files that may be used for tooling in manufacturing. Designers now have control over subtleties of form in production parts that were not available 20 years ago.




Fig.4 - Screen capture of Maya window.

 
Maya, design software offered by Autodesk, represents a gold-standard in visualization capability that extends from industrial design to entertainment design and animation. It is so powerful that many designers know and use only a portion of the total package.


With the capability, however, comes daunting complexity. Visualization tools and controls not only construct surfaces and images using methods and protocol foreign to building methods used in real life, they are governed by new vocabulary and language (Fig.4).





Fig.5 - Close up of Maya window.

 Sets of menu systems, macros, and iconography must be searched, investigated, experimented with, and learned largely by regular use to begin a development system for computer visualization (Fig.5). Multiple menus may perform similar if redundant tasks offering different ways to do the same thing while adding complexity to system understanding.


Currently, scientific literature is more complete documenting the creative cognition associated with drawing versus computer visualization. Future studies may show parity in the two processes.


Drawing and computer processes both require different thinking to translate ideas to 2D images. I'll explore those protocols in more detail next.

Abstract

The intent of this site is to to make connections between the two mediums, drawing and computer visualization, for the practice of Industrial Design. Both disciplines are well integrated into the processes of design but a working relationship in education, how each can enhance and illuminate the other, has not been firmly established.

The current trend in design education requires students to learn both disciplines of visualization compared to curriculum of 20+ years ago that focused mostly on traditional drawing and drafting techniques. Evidence from local design schools and professional opinions indicates that students’ knowledge base of drawing skills has degraded respectively with the required equal focus on digital media.

Given time/budget/curriculum constraints of most design schools, the search should focus on using existing curricula more efficiently or in conjunction with each element to help students gain the necessary skills to be competitive in the design marketplace. This study will seek ways to integrate both traditional and digital media to simplify and accelerate the learning process.

Using a benchmark of simple geometric shapes, weekly concurrent visual development in both traditional drawing and state-of-the-art computer rendering techniques will be posted online. Viewer responses are welcome.

This structure will represent an emerging protoype to help students and professionals blend the advantages and cognitive disciplines of one to inform the learning of the other.