tech 104 – technical graphics communication week 13: 3d modeling basics

TECH 104 – Technical Graphics Communication

Week 13:

3D Modeling Basics


The 3D model is…….

1. The visible representation of the database

2. Holds all its data within the structure of the model

3. Can be edited using Boolean Logic and other commands to add chamfers and fillets, etc.

4. Constructed from 2D geometry and other 3D models

Week 12: 3D Modeling Basics


We already know that within the realm of the 2D world, that all points within a plane can be plotted using the basic XY axis grid system.



Within the 3D coordinate system, a third axis (Z) is added to allow for the construction of volumetric solid and surface models.



As we have already seen, a 2D rectangle can be extruded (pulled) into a 3D prism.

Here we can also see the address of each vertex displayed with their X,Y,Z values.



The UCS icon shown at the bottom of the drawing interface here appears in its 2D format. In this environment, we can construct the foundational 2D components of a 3D model.



For 3D models, we must use an environment that allows for a volumetric model to be constructed. The “Right Hand Rule” allows us to understand the use of 3-axes.

Axis names are given to the first 2 fingers and the thumb.



Points in space can be located using a variety of methods. Here polar coordinates are entered to identify the basic shape that will be extruded into a cylinder along the Z axis.



REMEMBER: When constructing the 2D foundational components of a 3D model, geometry may be created using both absolute and relative commands.

Absolute values Relative values Week 12: 3D Modeling Basics


As we will see, should we wish to add supplemental coordinate systems, we can attach additional local coordinate axes to any part of a 3D model.



Wireframe models, or features within a 3D model, may appear ambiguous due to our visual orientation.



Solid “primitives” (basic 3D geometric shapes) can be combined to make complex 3D models.



Simple primitive shapes, can easily be put together using Boolean logic to create complex solid models.

Let’s look at an example……



Here, we can see that cylinders and cones have been added to prisms to create the basic box shape of the camera.

A wedge is then added to the top to form the view finder.

A cylinder is added to form the film case, and a subtraction was used to provided the angular shape needed.



Primitive data can be unioned (added) subtracted, or intersected (shared) with other primitives.

NOTE:

SUBTRACTION is also known in modeling as DIFFERENCE.



Using the UNION command, we are able to join the 2 parents into a new model.

This new model may be thought of as the “child” of the parent models.

As the child, the model will display some of the characteristics of each parent.


Subtraction (difference) is used to reduce data from one of the parent models.

Primarily, subtraction is used to create negative space, as well as convex and angular surfaces on the parent model.




Intersection is the only Boolean operation that affects only the data within both models that share a common address in space.

Any of data which is not “holding hands” with other pieces of data is ignored in this operation.



Here we have the outline only of 3 standard orthographic views of an object.



The profiles are then arranged in 3D space to show their true alignment with the X, Y & Z axes.



Each of the profiles is extruded a distance great enough to pass through each solid component.

When using intersection, each component’s length is unimportant as long as they each extend past the other components.

Remember: Only data that shares common space will be used to create the model.



What will the final model look like?…

…A combination of each profile!Week 12: 3D Modeling Basics


Consider these two profiles of a solid model…

What will the final model look like?



Step 1: Align the profiles

Step 2: Extrude the profiles and subtract the cylinders

Step 3:Intersect theparent models



Boolean operations use expressions to describe their procedure:

For example:If we had the expression:

(A+B)-C

…we would, union A to B, and then subtract C

from the result.NOTE: Boolean expression follow normal

mathematical rules of order.



Therefore, (A+B)-C, would result in…..



2D geometry of any shape can also be used to generate a 3D solid model. This is done through a variety of sweeping operations.

Here are some examples…..



Linear sweeps are also known as “extrusions”:

Extrusions may be parallel to the Z axis, or move in the Z direction at an angle.

NOTE: in 3D space the names of the axes change:

Z becomes W….X becomes U….Y becomes V



Revolving a “profile” (2D shape) around an identified axis is an example of radial sweeping.

Here, we can see that the profile may be revolved in a full 360 degrees, or in a specified number of degrees less than 360.



Sweeps may also follow a specified path. When the path enters space above the XY construction plane, the geometry used to create the path becomes known as a “space curve”.

Extrusions that are parallel to the Z(X) axis, may also be “tweaked” as shown in Example (B).

Tweaking allows a circle that would normally become a cylinder, to be extruded as a cone shape.



Here, we have an example of a solid model created by sweeping and Boolean operations.



Vehicle Examples



Week 14:

Solid Modeling…continued!


tech 104 – technical graphics communication week 13: 3d modeling basics

Documents

d modeling basicstech

d components

d geometry

d modelsweek

d world

d rectangle

d prism

d format