CAD Lighting

There are four different types of lighting available when rendering in a 3D modelling package. These are:

  1. Ambient light
  • Provides a constant illumination to all surfaces of a model.
  • Is always there and does not originate from ant particular source.
  • Ambient light on its own does not produce good rendered images.
  1. Distant Light
  • Gives a parallel beam in a particular direction
  • The user specifies the target point and the light source location.
  • Think of a torch shining on an object.
  1. Point light
  • A point light emits light in all directions from its position.
  • The user specifies the point light location.
  • Think of a light bulb.
  • Point lights are used for general lighting effects.
  • Point lights are used with spot lights for lighting effects.
  1. Spot Light
  • Gives a directional cone of light.
  • The user specifies the direction of the light and the size of the cone.
  • The intensity of the spot light diminishes with the distance from the model.
  • Spot lights have hot-spots and fall off angles that determine how the light diminishes at the edge of the cone.
  • Spot lights can be used to highlight specific features on a model.

3D modelling terms

Thickness

Thickness is an object property that gives the object a 3D effect. If you apply thickness to lines, circles, ellipses, arcs, polylines, solid fills, and traces they will acquire some height. Thus by changing the shade mode they will look like 3D surfaces and/or solids.

Ruled Surface

TABSURF and RULESURF are two of those commands that create 3D Meshes. The first command builds a surface with the help of a path curve and a vector. The second one connects to curves with a 3D mesh. Both commands are affected by the value of SURFTAB1 system variable.

  • Revolved Surface (surfaces created through revolution)

The REVSURF command enables you to create a surface, based on the revolution of a curve about an axis. The curve can be a line, spline, polyline, arc, circle, ellipse, or elliptical arc. The SURFTAB1 and SURFTAB2 system variables control the number of divisions in the final 3D mesh

Solid Primitives

A primitive solid is a ‘building block' that you can use to work with in 3D. Rather than extruding or revolving an object, AutoCAD has some basic 3D shape commands at your disposal. From these basic primitives, you can start building your 3D models. In many cases, you get the same result from drawing circles and rectangles and then extruding them, but doing it one command is generally faster. Using these with Boolean operations can be a very effective way of drawing in 3D. There are 6 six different shapes that you can choose from

SHAPE / COMMAND / ICON / DESCRIPTION
BOX / BOX / / Creates a solid box after you provide 2 opposite corners.
SPHERE / SPHERE / / Creates a solid sphere from a center point and radius.
CYLINDER / CYLINDER / / Creates a straight cylinder from a center point, radius and height.
CONE / CONE / / Creates a tapered cone from a center point, radius and height.
WEDGE / WEDGE / / Creates a triangular wedge from 2 opposite points.
TORUS / TORUS / / Creates a torus (donut shape) based on center point, radius and tube radius.

You can use the Boolean operations to create complex solid models out of primitives.

Intersect: Defines a new solid object based on the common volume between selected solids.

INTERSECT (same in Inventor)

This command creates a new solid from the intersecting volume of two or more solids or regions. AutoCAD will find where the two objects have an volume of interference and retain that area and discard the rest. Here is an example of this command shown below:

The INTERSECT command combines the volume of one or more solid objects at the areas of interference to create one solid object

Union/Join: Defines a new solid that consists of common and uncommon volume between selected solids.

UNION (Join in Inventor)

Below left, there is a box and a cylinder. These are two separate objects. If you want to combine them into one object, you have to use the union command.

The UNION command combines one or more solid objects into one object

Subtract/Cut: Select two set of solids. A single solid based on the removal of the second set from the first one will be created

SUBTRACT (Cut in Inventor)

The subtract command is used to cut away, or remove the volume of one object from another. It is important to check the command line when using this command. Remember that AutoCAD always asks for the object that you are subtracting FROM first, then it asks for the objects to subtract. Here is an example:

The SUBTRACT command removes the volume of one or more solid objects from an object
COMMAND / INPUT / ICON / DESCRIPTION
UNION/JOIN
(Boolean) / UNI / / Joins two or more solids into creating one based on the total geometry of all.
SUBTRACT/CUT
(Boolean) / SU / / Subtracts one or more solids from another creating a solid based on the remaining geometry.
INTERSECT
(Boolean) / IN / / Creates a single solid from one more solids based on the intersected geometry.