AVS as a Design Tool For Woodworking
				   
			    Larry Gelberg
		     Advanced Visual Systems Inc.
			      May, 1993

1. Introduction
The Woodworking Design Process When a craftsperson and a client work
together to design a commissioned piece, there are several factors
which must be discussed: 

	* Function - How will the piece be used?
	* Dimensions - How will the piece fit into an existing space?
	* Style - What existing furniture will share the space?  What
		materials will be used?
	* Cost - How complex is the piece?  How much and what type of
		wood will be purchased?
	* The Woodworker's Skill - Can he build the designed piece?

The process is frequently an iterative design cycle where the client
specifies requirements, the woodworker sketches out a general concept,
and together they refine the design.

AVS can be a valuable tool for prototyping completed pieces in three
dimensions.  The ability to create accurate, 3D models which can be
rotated, refined, and viewed under a wide variety of conditions (wood
texture maps, finishes, etc.) has proven useful in getting the
woodworker and client to converge on an agreed-upon design.

AVS as a Design Tool I am an amateur woodworker (who sometimes gets
paid for pieces!) who is also comfortable writing AVS modules.  It was
a natural fit that I should write some modules to help visualize some
of the pieces I was designing.  There are four modules in this
Woodworker's Suite which satisfy most of my design needs.

AVS provides me with images that I can share with my clients so that
we both get a good sense of how a completed project will look.
Besides the aesthetic design help, AVS gives me several technical bits
of information that I find useful for building the project: accurate
measurements (all the units are in inches, so I can relate the design
to real-world structures) and a volumetric measurement called
board-feet.

Lumber is purchased in a quantity called Board Feet which is 12 inches
by 12 inches by 1 inch of wood.  By computing the volume of wood in a
project (in cubic inches) and dividing by 144, AVS tells me the number
of board-feet I need to purchase.  I add on an additional 25% to
accommodate irregularities in the wood, layout problems, and mistakes.

2. The Woodworker's Module Suite
There are four basic modules in the suite; three of the modules
generate AVS geom objects which represent the different parts that
make up a piece of furniture.  The fourth module generates a grid for
measuring the pieces.  Since I don't own a lathe, every piece of
furniture I make is composed of one of three types of pieces: boxes
(boards), tapered boxes, and extruded shapes (boards cut into curved
shapes with a bandsaw).  

Cabinet Maker:
This is the box builder used to create collections of boxes simulating
hexahedral boards.  It has several features: 

	* Up to 100 boards can be specified
	* Per board dimensions can be specified
	* Translations and Rotations can be specified on a per-board
		basis
	* There are several coloring options: white, random, and
		wood-like (pseudo-random colors restricted to woody hues)
	* UV normals are generated for supporting texture mapping
	* It computes board-feet based on the volume of all the active
		boards
	* It can read and write simple ASCII board files

Taperer: 
This module is a refined version of the Cabinet Maker module that
allows each board to have a taper applied to it over its length. 
This taper is defined by specifying the dimensions at each end of the
board's length.  

Extruder:
This module simulates the effect of cutting a curved piece out of a
board with a bandsaw.  It reads in a profile curve file which contains
a list of 2D curve coordinates and generates a surface which is a 3D
extrusion of the curve.  Options include: 

	* Generating caps on the ends of the extruded tube
	* Current Limitations: does not generate UVs for texture
     		mapping, cannot	cap wildly concave shapes

Grid Generator:
In order to measure the lengths of the boards, a module which
generates a grid in each orthogonal direction was constructed. The
features of this module are: 

	* Different English grid dimensions are drawn in different
		colors:	1 foot, 1 inch, 1/2 inch, 1/4 inch, 1/8 inch,
		1/16 inch
	* XY, YZ, XZ grids can be individually turned on and off
	* The origin of grids can be displaced 

3. Case Studies
Coffee Table:
The client wanted a coffee table of specific dimensions constructed
out of a wood which would match her existing furnishings. Furthermore,
she wanted the table to be collapsible so that it could be easily
taken down and stored. 

We originally designed the table shown in the AVS images intending
that the legs would be hinged and fold down onto the bottom of the
table.  This concept was abandoned when we could not decide on an
effective bracing scheme and when the client also requested a
removable middle shelf.

As you can see in the final photograph, we selected an exotic wood
called Padauk because of its orange-red color.  The legs ended up
being braced against each other diagonally and the middle shelf sits
on the crossing braces.  The bottom of the table top was routed out to
accept the tops of the legs for further stability.

Four Poster Bed and Matching Nightstand:
The client in this case wanted a four poster bed to support a futon
mattress.  Shaker styling for the bed and nightstand was selected for
the simple lines.  The two pieces were rendered in Curly Maple and
Purple-Heart. 

AVS played an invaluable role in refining the variable design
parameters: the height of the mattress off the ground, the curvature
of the head and foot boards, and the appearance of the Maple and
Purple-Heart woods next to each other.  Note that the ellipse of the
backsplash on the nightstand is geometrically similar to the head- and
foot-boards.  The coordinates in the profile curve file which defined
these ellipses was used to transfer the shape to a template which was
used to mark the wood.

The taperer and extruder modules were specially written for this
project to generate the tapered legs as well as the curved portions of
the model.

Jewelry Cabinet:
Compared to the other projects, this was a straight forward design.
The client wanted a wall-hung jewelry cabinet which would have both
drawers for storing small items as well as a tall, open area for
hanging necklaces.  Two designs were evaluated.  The rejected design
had the cabinet divided into two sections horizontally, the top half
for hanging necklaces and the bottom half for drawers.  We ultimately
settled on dividing the cabinet in half vertically and using one half
to store both drawers and shelves. 

An interesting design note: the dimensions of the front of the cabinet
correspond to the Golden Rectangle, a shape of historic aesthetic fame
whose sides correspond to the ratio: 1.618 : 1.

The texture-mapping feature of AVS can be used to evaluate various
potential woods.  In the image shown, you can see simulated Oak, Pine,
and Plywood.  We ultimately settled on Bird's-Eye Maple, Mahogany, and
Koa (the inset panel on the door) for the final piece.

4. Future Work 
While AVS proven extremely helpful in creating images for evaluating
woodworking designs, the modules described here do not comprise a
complete drafting system.  In many woodworking books and magazines,
there are usually detailed measured drawings showing exploded views of
many of the components that make up a piece of furniture.  Measured
drawings produced by such drafting tools frequently include features
such as: 

	* Complex joints: miters, rabbets, dadoes, and dovetails
	* Automatic dimensioning
	* The ability to readily explode a model's pieces
	* Turned elements such as those produced on a lathe

If these modules were to become the backbone of a professionally
complete design tool, they would require that these features also be
added.