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3D Sculptor 3D Sculptor - a professional CAD engineer who uses Surfacing; also known as Surfacing Engineer


the rate of change of the slope of a curve or surface. An arc, which has constant curvature, has zero acceleration.
antitangent not a real word, but "anti-tangent" is sometimes used in modelling circles to describe two surfaces that are tangent to each other but meet at a cusp (a sharp edge). ie. they are 180 degrees from tangent.
arc a segment of a circle. Arcs are primary building blocks for curves and surfaces.
aspect Ratio describes the proportions of rectangular type shapes. A square has a low aspect ratio (1:1). A long plank of wood has a high aspect ratio
base Feature in CAD construction this describes one of the primary features onto which more detailed construction is then added. At the end of the model build there may be little left of the base feature even though it may still be recognizeable.
beltline an automotive design term describing the waistline of the car.
bevel the inclination between 2 surfaces when they are not at 90 degrees.
bezel a mostly decorative part surrounding an important element of a device. A bezel is often a metal or plastic band that both covers a gap between 2 parts and also adds a finishing touch to the design. Examples could be a watch bezel or the trim around the display on a TV or the decorative chrome around the lights on a car.
bezier a bezier curve is a parametric, polynomial curve popularized by Monsiour Bezier who made car bodies. Most commonly, they are quadratic and cubic mathematical expressions.
blend a surface that transforms, or "blends", from one section to another.
blister a tight, convex, bulbous form that grows out of a larger base surface.
boolean British mathematician, George Boole, invented boolean algebra with which all computers operate. A boolean union combines 2 geometric forms. A boolean subtraction removes one 3D form from another.
bounding box the smallest rectilinear box into which a 3D feature, model, or assembly will fit.
B-spline a B-spline or "Basis spline" is a parameterized spline curve related to a Bezier curve.
bulge I think you know what a bulge is. A bulge is most likely to be a soft form with continuous border where it meets the base feature. Remember it is the base surface that is bulging out rather than a discrete protrusion that is being added on.
CAD Computer Aided Design. Software such as Unigraphics, Catia, or Pro/Engineer
CAD monkey anyone (almost exclusively male) who uses CAD
chamfer an angled surface created by sweeping a straight line around the outside edge of a part.
character line a crease in the bodywork on the side of a car to create interest. Same as swageline.
chine a chine is a hard or soft edge between 2 surfaces on a boat that run down the length of the hull. One can have one, two, or three chines depending on the construction. Chines origininated because of construction limitations rather than performance. When using rigid, planar material such as plywood, where two boards meet there will frequently be a hard edge.
chord a straight line drawn through 2 points on the circumference of an arc or circle.
chord length when creating a tesselated file for export, one typically has to specify the maximum chord length which effectively becomes the maximum width of each facet.
class A surfacing a poorly-defined term that relates to the quality of surface construction. Mostly associated with the automotive industry, it stresses the avoidance of imperfections when creating large, glossy, non-textured surfaces. Many people associate class A surfacing with curvature continuity.
closed quilt a continuous quilt or surface that contains a fixed and defined volume and has no openings can be described as a closed quilt. A solid can be created from a closed quilt.
coke bottle distinct modified hourglass shape in which the upper part is smaller and has a smaller diameter than the main lower part of the bottle.
concave a curved, "hollow", surface where the surface normals point towards each other such as the inner surface of a sphere.
cone a cone is a fundamental 3D building block like a sphere or a cube. A cone is an example of a "ruled surface".
conic a curve that is created by intersecting a cone with a plane. Possible examples are hyperbola, parabola, ellipse and a circle.
construction history history is a element of parametric CAD programs that enable an engineer to redefine, reorder, and evaluate individual features that have been created to construct a model. Programs which don't have history force the user to reconstruct the model when making most significant changes.
contiguous you can use this word to describe things other than 48 American states. Contiguous simply means unbroken, connected or continuous.
continuity continuity can refer to positional continuity (G1), tangency (G1), curvature continuity (G2) and higher. The greater the continuity, the less noticeable will be the point or boundary between two curves or surfaces.
contour a contour is mostly used to describe in 2D the form of a 3D body. It really just means the outline of something. With a contour map, this outline is created by intersecting a flat plane with the 3D geometry.
control vertex CV a control vertex is the "handle" of a B-spline that enables a user to manipulate a parametric curve. A single span for a cubic B-spline will have 4 CV's.
convex the opposite of concave. A convex surface is curved in three dimensions such that the surface normals point away from each other. An example would be the outer surface of a sphere.
cookie cutter an extruded cut made in a surface is sometimes described as a "cookie-cutter".
COS curve on surface many CAD packages provide the ability to create and modify a curve that is entirely on an existing surface. This method can be compared with creating a two dimensional curve and then projecting it onto a surface.
crease a precise, smooth bend in a piece of sheetmetal similar to a crease in a piece of paper. Creases are created in a press by a simple or progressive die.
crown a "crown" or "crowning" is the addition of convex curvature to a protrusion (like the crown of the head).
cubic an equation to the third degree is described as cubic. They are more flexible than second degree curves which are called quadratics. Incidentally, if you are researching for the the ark-building trade, a cubit is 18 inches or 45.72 cm.
curvature the degree by which a non-linear or surface curves. A straight line or plane has zero curvature. The smaller a radius, the greater the curvature.
curvature continuity two surfaces that are curvature continuous (G2) have the same value of curvature across their common boundary. A curve or surface that has curvature continuity also has positional and tangency continuity.
cusp a cusp is a sharp edge on a surface that may be a modelling defect and will probably be difficult to mould or machine. Think of a cusp as the tip of an ocean wave that is about to break. Strictly speaking, the two surfaces that meet at the cusp should be tangent (antitangent) to each other.
cut-line this is used mostly in automotive circles to refer to the line or gap around openable parts of the bodywork such as the doors, bonnet, and boot. Also called split-line
datum a fixed reference feature such as a plane, axis, or point
deboss not a proper word. Don't use this in public. De-boss is used as the opposite of emboss. A deboss is created when a surface is lowered locally in a pre-defined shape. They are frequently associated with the creation of a logo or pattern on the surface of plastic
dog leg an element of a design that resembles the back leg of a dog. For example, the distinctive line of a BMW "C"-pillar.
draft an american spelling variation of draught
draught the beveling of a surface in a constant direction in order to make it mouldable. Depending on the material, texture, and geometry, a minimum angle will be required for all surfaces in order to injection mould or cast the part.
ellipse an ellipse is a type of conic section which resembles an oval. An ellipse can be defined by a major and minor diameter. In CAD, a partial ellipse can usually be constructed that is basically a quarter of an oval. Here, apart from the beginning and end points, the ellipse is defined by start and end angle vectors and a rho value. Rho varies between 0 and 1 where 0 would be a straight line and 1 is a sharp corner. A pure ellipse has a rho value of 0.414
emboss to raise the surface locally in a pre-defined shape for decorative (logos, etc) or functionally (bosses, etc) effect. Designers also tend to use "de-boss" for the opposite of emboss.
engrave if you cut your girlfriends name into the bark of a tree you are not only a sap and a vandal, but also an engraver. Engravers typically work in the jewellery field. An engraved feature could also be described as a "de-bossed" feature.
exercise same as "flex"
extend an extension of an edge of an existing surface that is at least tangent or curvature continuous is called an extend.
extrusion if you take any two dimensional shape and and translate this shape normal to the plane of the sketch, you will have an extrusion. This is the most fundamental feature in CAD and is no different than using a shape cut into a die to make a plastic or aluminium extrusion.
fade a way of describing a surface feature that is quite pronounced at one point and then fades to a smaller or softer form or indeed disappears alltogether.
fair, faired, fairing a fairing is the streamlined, fibre-glass shell that makes a motorcycle faster and more slippery to the wind. It is also the process by which spline curves are smoothed out or "faired" to make them softer. You are most likely to "fair" a curve or surface digitally. People that build surfboards or wooden boats often do their fairing manually.
faceted a model that is "faceted" is comprised entirely of triangular or rectangular faces. This way of creating or saving data is very useful for several applications such as rendering, rapid prototyping and finite element analysis.
fascia  a zone that is probably planar typically on the front of a product or component that is frequently used for decoration or logos or to mount controls or instrumentation.
feature virtually all created entities in the CAD world can be described as "features". They don't need to be geometric features. They could also be datum features. With parametric, history-based, CAD, each feature will be a seperate entity in the model tree.
fillet a fillet is the addition of material at the intersection of two surfaces in order to make a smooth, tangent connection. A fillet always adds material, whereas a round removes material.
flex in parametric CAD circles, flexing the model means ensuring that the part is robust by changing dimensions or parameters and checking to see that it doesn't fail. This is very important if you work in a large corporation and many other people will be working on your part. It is extremely important if your part will be modified and saved so as to create a family of similar parts.
flow flow is an important attribute to many industrial designs. Frequently, surfaces must be seen to flow seamlessly around the product without irregularities such as pinching or puckering.
flush a surface that is in line with another surface is flush (they both protrude by the same amount).
freeform freeform surfaces are complex surfaces such as NURBS that have been manipulated by pulling on CV's. They are not parametric.
G0 continuity see positional continuity
G1 continuity see tangency
G2 continuity see curvature continuity
gaussian analysis gaussian analysis evaluates the gaussian curvature of a surface. This curvature can be positive (for convex objects like a sphere), zero (for ruled surfaces), and negative (for concave surfaces).
geometric geometric forms are comprised of geometric elements such as rectangular extrusions and spheres, etc. Contrast geometric shapes with organic ones.
hard points hard points are used to represent the location of critical elements in the design around which everything else will be layed out or designed. In many cases, these hard points will actually be axes, planes, etc.
hourglass you can use the word hourglass to describe not only your favourite girlfriend but also some product designs. Another option is "peanut" but your girlfriend may not be so keen on that one.
hybrid modeller a hybrid modeller combines the functionality and advantages of surface modelling and solid modelling.
inflection an inflection is a point on a curve where the curvature changes from one direction to another. For example, the profile of a wine glass will have an inflection point where it changes from concave to convex.
iges Initial Graphic Exchange Specification. A neutral data exchange format that uses ASCII to define geometry in order to transfer it to another CAD program (for evaluation or machining, etc). IGES was defined in 1980. It has largely been superceded by STEP.
interpolation interpolation is figuring out the intermediate values inbetween the values that you are sure about. When you create a curve or surface, your CAD program will interpolate the necessary values between the points and curves that you provide.
isoline an isoline is a curve that connects all the points on a surface that have equal values. If the value is height, then isolines are the same as geographical contour lines.
isoparm short for "isoparametric curve". By definition its any curve running across the entire width of a nurbs surface that is parallel to either the u or v direction of the surface. In reality, isoparm is used to refer to any visible internal curves on a surface or quilt. ie. any curves that aren't edge boundaries. These internal curves are created when one of the boundaries on a 4 sided surface is comprised of 2 or more curves.
knot as you know, each spline is comprised of a number of pieces each of which are defined by a polynomial. Between each of these pieces is a "knot".
lathe a lathed surface is one that has been revolved (on a lathe) around a fixed axis.
lattice structure one approach to surface model building is to create an elaborate network of inter-connected curves that are then used to create boundary surfaces. Some people use "lattice structure" to refer to this curve network.
linear linear refers to a straight line (geometry) or a uniform rate of change of function. ie. something that increases or decreases in a constant fashion rather than the accelleration or decelleration that would be the result of using a quadratic or sine function, etc.
loft a loft is a type of surface construction. Lofted surfaces smoothly connect 2 or more curves in a continuous fashion. In Alias a loft is called a skin. In Pro/Engineer it is called a Blend.
match surfaces when creating surfaces, there is frequently an option or necessity to join the new surface to existing geometry. A surface can be "matched" to its neighbour with either positional, tangent, or curvature continuity.
merge a merge is a boolean union between 2 surfaces.
nacelle This is a nice word that has its origins in the Latin word for boat. Today, it is mostly used to refer to the streamlined enclosure for an aircraft engine. Nacelle also is used for any kind of bump, blister, or housing that houses the crew on a hot air balloon, aircraft, or dirigible.
nurbs Nurbs are a specific mathematical definition of a curve or surface. Nurbs stands for non-uniform rational B-splines, where the "B" refers to Monsiour Bezier. Bezier was an engineer at Renault in the 1950's and also a clever bastard. Nurbs are defined by their order (mostly 1,2,3 or 5), their control points (points in space that can be dragged around), and knots (these provide control on how much the control points influence the curve).
obround A 2D shape that is a combination of oblong and round. Its basically 2 straight, parallel lines connected by 2 semi-circles at either end. Another word for obround is racetrack. Obround is most frequently used in the world of sheetmetal punches where they are used to provide clearance holes for bolts.
ogee A shape where a convex curve flows into a concave curve. This form is most commonly found on architectural details such as crown moulding.
organic organic surfaces tend to be smooth, soft, and flow together seamlessly, possibly resembling forms found in nature. They may also be asymmetrical or blobby. One might say that the opposite of organic is geometric.
oval A generic term for an egg-shaped form. It is not well defined like an ellipse and can refer to a variety of symmetrical and asymmetrical (eg. eggs) shapes.
overbuilt A construction technique whereby surfaces are created that are larger than necessary. This ensures that there will always be a clear intersection line when trimming or merging (surfaces that are built line-to-line may run into tolerance related failures when merging). It also makes the model more robust in the sense that it can be scaled up during future design changes with less chance of failure.
ovoid something that looks like an egg.
parabola A "U" shaped conic section that is frequently found in natural forms. An path of an object, such as a cricket ball, thrown in the air can be defined by a parabola.
patch the smallest element of a nurbs surface is a patch.
perforated something with lots of holes in it.
pillow(ed) a pillowed surface is one that is plumped up (like a pillow). Same as a crowning except that pillowing is almost exclusively associated with 3D whereas crowning can refer to 2D.
pip a pip is often used to define a tiny geometric bump on a surface. An example might be the pip for blind people found on the number 5 key of most cellphones.
pivot direction in Pro/Engineer, the pivot direction was a term used to describe a type of variable section sweep. The section being swept was always aligned with the pivot direction. It is now called "normal to projection". I used to think of an upright soldier square-bashing and pivoting on one foot when making a turn. His body is the constant normal or pivot direction with respect to the ground. I'm sure that's not what they had in mind.
positional continuity this is the lowest level of continuity. Two curves or surfaces that are connected at a point or along an edge, but are not tangent or curvature continuous, have positional continuity (G0).
proud a surface that protrudes more than its neighbour can be described as proud. Compare with recessed and flush.
punched a solid or surface that has an extruded cut made through it, can be described as punched. Same as cookie-cutter.
quadratic A second-order equation.
racetrack A rectangular shape with a full-round at both ends. Same as obround.
rail A rail is a trajectory along which a curve can be swept to create a 3D surface. Such a sweep may have one or more rails.
rake Rake describes the angle at which something is designed with respect to the vertical. For example, a streamlined car might have a heavily raked windscreen.
revolved surface a surface that is created by rotating a section around a fixed axis.
ribbon A surface with a short, straight, constant cross-section that sweeps along a 3D trajectory. In surface construction, ribbons are often used as structures to define tangency for boundary surfaces.
robust A 3D model can be defined as robust if random features can be modified slightly without the model failing. Making changes to verify robustness is known as "flexing" the model.
round a round is the softening of an edge by the removal of material. The new surface is tangent to the original two surfaces. If the edge is at the 90 degree intersection of two planar surfaces, the round is a quarter-round (a qudrant of a cylinder sliced longwise). Rounds are normally circular in section, but some CAD programs also allow for conic rounds. Rounds are similar to fillets.
ruled surface a ruled surface is one that can be produced by sweeping a straight line along a trajectory. Planes, cylinders, and cones are examples of a ruled surface. All ruled surfaces have zero gaussian curvature. An understanding of ruled surfaces is useful for designing parts in sheetmetal. All sheetmetal parts that need to be "developed" must be comprised of ruled surfaces (in order to create a flat pattern).
saddle point the point on a surface that is shaped like a horse saddle. Seen from one direction the surface forms a "u". Seen from another direction (at 90 degrees) it forms an "n". The form can also be compared with the shape of a mountain pass.
scan data the mass of point data that is created when an object is digitally scanned with a laser scanner. This raw data is typically then processed to create more useable file types, such as tesselated data or nurbs.
scoop scoops are air intake devices frequently found on the bonnet of cars. A scoop can be used to describe many oriented inlets to a fixed volume.
sculpt the act of adding or removing material in real life with real materials or digitally with Computer Aided Design
shell a shell is a wall of constant thickness. A solid that has its insides "consumed" to create a thin wall is said to be "shelled out" (think of a snail being removed from his/her shell)
skinning skinning is another word for lofting which is creating a smooth, continuous surface through 2 or more curves. The term "skinning" is frequently used by Alias users.
soft point soft points are points on a spline that reference existing geometry. They are created by the user during construction of the spline by selecting an edge or vertex. They are "soft" in the sense that the spline will be forced to update when the referenced geometry changes.
solid model in 3D CAD terminology a solid model is once that has a finite closed volume that can be measured. Any closed surface can be made into a solid. Solids can be added to an subtracted from each other using Boolean operations. When removing material from a solid, the part is cut whereas for a surface it is trimmed.
spline A 2D or 3D curve defined piecewise by polynomials. The term piecewise simply means that different polynomial expressions are used to define the curve for different pieces or sections of the curve. A spline is a simplified approximation of what might otherwise be a very complex mathematical expression. A Bezier curve is an example of a spline. The term "spline" is borrowed from boatbuilding where it refers to a thin strip of flexible wood (in East Anglian dialect). This wooden strip held between two fixed points on what will become the ships hull assumes a smooth shape in order to minimize the energy held in the wood. Wooden splines were also used in the early days of aviation and automobile design.
split line the common line or split between 2 adjacent components. See also cut-line
spoiler a spoiler is an aerodynamic device that is attached to a car that may be used to increase downforce by reducing the air going under the car or by directing air by means of a wing type design.
spun surface see revolved surface
step Standard for the Exchange of Product model data. STEP is an ISO standard (ISO 10303) and is used to transfer model geometry data between different CAD programs. STEP is a more robust alternative to IGES.
strake strakes are two different but related things depending on whether you're discussing boats or planes. For boats, they are the long planks of wood or steel that run longitinally down the boat to create the hull. For a jet plane, strakes are an extension of the wing that runs along the fuselage of the plane to create improved aerodynamics.
surface modeller any CAD program such as Rhino that models with surfaces. Naturally, it follows that one uses a solid modeller to create and modify solids. Most mainstream CAD programs such as Pro/Engineer and Solidworks are known as hybrid modellers since they can function in a mixture of both modes.
surface normal all points on a surface have associated surface normals (normal simply means a vector at 90 degrees to the direction that the surface is going). It is typically more convenient to use the surface normals rather than a surface tangent vector. The surface normal is also used to define which of the 2 sides of any surface is the positive one. This is akin to describing the inside and outside of a surface. This (mathematical) information is used to decide what happens when merging 2 surfaces together.
swage line a swage line is any raised styling line or crease on an automobile such as the beltline. Some time back, it was not possible to create an entire door from one piece of sheetmetal. Instead, two stamped pieces were swaged (mechanically joined through deformation) together to create a single part with a raised line through it.
sweeten to refine curves in order to improve surface aesthetics. This may be a matter of eliminating defects, improving smoothness or flow, or simply adjusting the design.
tangent two curves can be described as being tangent at a given point if they point in the same direction at that point. Surfaces that are tangent to one another across a common boundary join are joined together in a reasonably smooth manner.
teardrop teardrop can be used to describe a shape that is basically a triangular form with a full round at each end.
top-down the best way of describing "top down" is to describe the opposite which is "bottom up". If you start to build a model by grabbing a bunch of Lego blocks and sticking them together, this is "bottom up" where "bottom" is the smallest part or feature in the model. If we start of by considering the space claim and functional requirements of the top-level of the assembly or part we are designing, this is "top down" design or construction. The lower level sub-assemblies and parts will all be driven by this initial high level design. In practice, when using CAD, these top-down considerations are controlled by a single "master model" that defines that boundaries of each part and the manner in which each part relates to its neighbour.
transition a transition is any region of variable geometry that, possibly a sweep or round, that allows a various parts of a design to fit seamlessly together, Unless you're designing a sphere or and I-pod, there's a good chance that your model will be comprised of various distinct geometric regions. These will be connected by transitions.
trim when surfaces are cut down to a smaller size, they are "trimmed". A solid is cut. A surface is trimmed.
tweak to "tweak" is to marginally refine a feature so that it meets functional or aesthetic requirements.
Utah Teapot the standard 3D reference model for rendering that was created at the University of Utah in 1975. The teapot is useful because it is a relatively simple model and yet looks very nice when rendered. It also contains convex and concave surfaces, saddle points, and is self-shadowing due to the handle and spout.
UV NURBS surfaces are constructed in two directions like a grid. The two directions are nominally called U and V.
vertex a vertex is a sharp point on a surface where two edges meet.
voxel voxel is the big brother of pixel. Whereas a pixel is the smallest element in a 2D image, a voxel is the smallest element in a 3D "scanned" image.
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