holiday color downtown

little case study

A client created a SketchUp model and was using it to move the project along. It was time to start raising funds from the community where this arts center would be built.
The model was manipulated to explore lighting and generate different views.
Different contexts and lighting were roughly composed for approval.

Progress scan.

Detail of final watercolor

linear perspective basics

Two drawings are needed to construct a perspective drawing. A third is often necessary, but can be embedded in the second. The first is a map that gives scalable, 2-dimensional information about the orientation of viewer-to-object. I call this the Setup. It's often a plan that includes the viewer's location (SP). What's missing is vertical measure: eye height above ground of the viewer and the height/elevation of the object. (that missing elevation is very often the useful third document) Kevin Forseth's book has very clear illustrations. Here is an example of a Setup from his book:
station point (SP): the putative position of the viewer

line of sight (LOS): a straight line, often parallel to the ground, from the eye of the observer to the center of a scene

cone of vision (COV, FOV) : a peripheral limitation to the field of view -- a cone whose apex is at the station point and whose angle is between 35ºmin-60ºmax

picture plane (PP): an imaginary plane, perpendicular to the line of sight, from which the scaled measure of objects may be taken. In a one-point perspective, the picture plane can be coplanar with an elevation or section.

horizon line (HL): appears to cross through anything standing at the same height above ground as the eye level of the viewer; once it has been assigned a numerical value, the height of volumes on the ground can be inferred. Its usefulness is broad but still limited, and works most predictably when the line of sight is perfectly horizontal and parallel to the ground.

center of vision/central vanishing point (CVP): The geometric center of a perspective construction. The point where the line of sight intersects the picture plane, and the vanishing point for any lines oriented perpendicular to the picture plane. A perspective composition can be cropped such that the center of the construction is no longer located in the center of the frame.

busman's holiday for perspectivists

A holiday for some. With no competition from the day job, a student perspectivist can buckle down, locate all the furniture in the interior perspective, figure out the height of the windows, indicate the ins-and-outs of door jambs, soffits and bay windows, bring it all to class tonight and -- heck, shed some light on it, too.

b/w interiors

Per student request, here are 3 black and white interior perspective drawings. Click on an image to view slightly larger. charcoal pencilink and marker
Images ©J.F. Mahoney, all rights reserved.

going deep

In the world of flat geometry, a right isosceles triangle has equal sized legs and a 45º angle. One can divide a vertically-striped plane into a grid of equal squares using the 45º diagonal.This same plane's set of parallel lines, when laid down into the geometry of linear perspective, appear as rays that converge as they recede. Their convergence is governed by the central vanishing point C in this diagram based on Kevin Forseth's useful book on perspective: Since we're no longer in flat space, a diagonal line is at a virtual 45º. A protractor laid on the drawing will not measure 45º.
The rate at which equal intervals diminish in size as they recede is a affected by how far the measured field/back wall/picture plane is from the observer. This process of representing space fixes the viewer's distance from the virtual scene. The distance between the viewer(SP) and the viewed object (in this case, the back wall) is related to the distance between C, the center of vision and the vpD, or diagonal vanishing point. A perspectivist can slide the back wall forward to make the viewer feel closer to it. 

Increasing the distance (on the HL) between the vpD and C, would flatten the virtual 45º diagonal, compress the receding intervals into a smaller space on the page, and give the impression that the scene is farther from the observer. Note that the size of the back wall is the same as in the drawing above. By moving the vpD away from the central VP, the "measured" distance, or depth, between that wall and the observer appears more compressed.

black holes

I had been working with a retail client on look-and-feel, sketching different phases of the retail experience with scenes unique to the new flagship store in Manhattan. The store design crew sent numerous product pics and architectural files to a 3d modeler, who created an animated fly-through for concept presentation to the company's CEO. Except for the fixture design, the layout and most of the interior details were complete. Their boss found the video stiff and unfriendly. Photos of product had been stretched like silly putty around shapes that didn't match the products' proportions. Product was sparsely distributed and -- nightmare to any retailer -- nobody was in the store! Perhaps most painful for the design crew (apart from the uncannily familiar soundtrack) was how details that had not been fully worked out appeared: black polygons! These virtual voids, stole a show that could have been about how well the space was working. The concept was presented again, using quick sketches, and it moved along, approved. Later, a technique was developed to embed the brand's proprietary video ads and music into online sketch presentations.

gimme scale

Most architects and planners now have their designs on a computer instead of paper, and an information void has opened. When it's time to share the design, we often rely on PDF format. Unfortunately, the scale of an orthographic drawing is not automatically translated to the PDF. Items that were grouped in CAD software no longer self-segregate in the PDF.

When a model shot is sent in PDF or JPG format, the situation becomes even worse for determining the actual measure of lines or objects. Although the CAD user-designer is one click away from measurements and attributes, the recipient of the PDF can only guess!

A design team, working from files shared on their server, has access to all the project information; members can check details not yet generated as a document page. Outside consultants must rely on PDF files. The designers cannot assume their consultants have updated project information in a source file as they do. Best practice: Gimme scale.
Leave a scale indicator or a literal dimension (55") on the image file that's enlarge/reduce-proof, or back up a PDF with a DWG file, which DOES contain scale info. A PDF update can be sent in moments, but a faulty dimension can lead to a chain of errors that take time and money to rewind. Alternatively, upload entire files for sharing with external consultants and notify when updating.

this magic moment

I've worked on both sides of the digital model debut. Before 3d modeling software was prevalent, the designers who could sketch their ideas freehand or with loosely constructed perspectives seemed to be in the minority. Another good indicator of visual thinking fluency was rough study modeling with cardboard and scissors. When designers who weren't sketchers themselves were shown how their plans become volumes relating in space, there was often a pause of disconnect. Maybe it was 'cause the right brain hadn't known what the left brain was up to. I suspect the designer was reintegrating the visually modeled reality with what had been in the mind's eye. Always a rich moment. Usually what followed was some kind of improvement.
3d modeling software has made that kind of integration -- or facsimile thereof -- possible for many who might never have learned to sketch in perspective or construct quick models. Hopefully it has enriched the design process while bringing earlier feedback on energy calculations and materials' cost.

digital vs. manual

Why do modeling programmers strive to have their machine make itself invisible? Computer modeling is approximating the look of a hand drawing to the extent that software decides how to threshold a CG "drawn" line so it is more pleasing, more appealing, more natural and looks "better".

I appreciate the different atmospheres between CG designers modeling a 3d volume and perspectivists illustrating a 3d volume from a plan. Each struggles to "lock in" to the space, but making a CAD model seems like typing while the pencil drawing, although rigidly procedural, retains that sensual friction between the medium and the paper as the mind's eye follows a virtual fold.
Very nifty that a perspective view residing in modeling software can report back the measure of the virtual volumes. Once extracted as a 2d file, it's as mute on that topic as the manual drawing.

scenography

Thom Ross undertook an interesting play on 2d and 3d that combines history and scenography at Ocean Beach in SF. The installation comes down September 15, 2008.

implicating the observer

If 7 people were to rely solely on your verbal description of a scene you experienced, each person might have quite a different picture in their mind's eye! Give each of those seven a map of the scene. Their internal pictures may shift, but still differ. If each were also given an elevation of the space, the individual perceptions might begin to align. How much would providing a perspective drawing ensure that those seven people are now "on the same page" in their understanding of the scene?

Constructing a linear perspective might be called a public relations task, a translation, or propaganda, where the perspectivist mediates between a purported reality and an audience.

Beginning with selection of the view itself, the perspectivist has a great deal of control over how a space is perceived. Traditional linear perspective fixes a relationship between the virtual 3d environment to be portrayed on a 2d surface and an observer. The distance between the observer and the environment, the height of the observer's eye level and the direction of the gaze can all be inferred from a perspective drawing. Put another way, the creator of a linear perspective establishes a relationship between a virtual volumetric space and its audience-observer. The observer can see no more of the space than what has been revealed in the linear perspective.

paraline drawings

Scaled orthographic drawings, such as plans, elevations and sections disclose the relative measure of only two dimensions at a time on a 2-d drawing surface. The viewer/user can put a ruler anywhere on the page to obtain information about the virtual object. Only 2 dimensions at a time can be related.
Machinists, cabinetmakers, architects and planners use paraline drawings to represent a third dimension on two-dimensional paper, while retaining the measured precision of 2-d orthographic plans, elevations and sections. Paraline drawings, while depicting objects "from above" or "from below," don't implicate any particular observer. Paraline drawings retain scalable lines useful to construction. Sets of lines that are parallel in the virtual object remain parallel in the 2-d paraline depiction.
Linear perspective drawings describe 3-d volumes and spatial relations on a 2-d surface as they appear to the fixed gaze of an observer --- the audience looking at the drawing. The observer is implicated in the virtual scenario.

early inspiration

Vince Collins on perspective.

linear perspective

One of the hardest skills to acquire as I became more self conscious about drawing was that of depicting space. I wanted ever so much to depict rooms with people in them and scenarios "beyond" the front-and-center. At university, Dennis Nechvatal handed me an illustration-free, 1930s how-to book on perspective. How NOT to!! Such dense text encouraged me to work it out on my own. Roger Tibbets heartily supported that effort, which has been the root of my understanding of spatial relations. A fascination with how we perceive and depict space and how visual images link us to deeper fields of information has fueled my studies and my work life.
For those who don't want to work out perspective drawing on their own, an abundance of well-illustrated books and websites covers the practice of linear perspective. Much dwells on the built environment as content. 3D modeling software, the slide rule for 21st century perspectivists, will do much of the work for us, faster than humanly possible. But it makes the process opaque, yields a less-than humane-looking product, and severs the proprioceptive feedback loop that makes drawing so rich. (Check out the dedication at the bottom of this page!)
I've taught perspective drawing (both measured and freehand) since 1981.