You'll spend a lot of time creating sketches - collections of circles, lines, arcs, etc. - as the basis for 3D models. It's important that this is easy to learn and fast to do. Alibre Atom3D has a great sketching environment.
An example of a 2D sketch and the resulting 3D model.
A 2D sketch is a profile on a plane - a cross section of a particular part of the 3D model. Sketches contain figures like lines, arcs, and splines, as well as reference figures, dimensions, and constraints.
Modifying the dimensions of a sketch will result in the sketch figures changing shape or location to match the new input. Design intent is built in with equations and 2D constraints like "Parallel" or "Concentric".
A 2D sketch that controls the general shape of this part. Only one side has to be defined because a mirror operation is used.
Core sketch figures define the geometry of your model. Lines, rectangles, circles, arcs, ellipses, polygons, and splines.
Reference figures are guides for regular sketch figures. Use them as a reference or mirror across them. Reference figures do not contribute to 3D geometry.
Create text figures to create embossed labels, logos, instructions, indicators, and more.
A sketch with lines, arcs, circles, and green reference figures that help with positioning.
Sketch Constraints like Parallel, Equal, and Symmetric enforce design intent upon sketch figures. An example of design intent is, "these 4 circles should always be the same size."
Constraints ensure that model changes are simple and true to the design intent. They also reduce the number of dimensions that must be created to fully define a sketch.
Constraints tell a model how to behave. Dimensions dictate the size and location of model components. Dimensions can be created on-the-fly or at any point.
Dimensions can be lengths or angles and can be between most any sketch figures or existing 3D model entities.
Build design intent into the model by using equations as dynamic dimensions. Reference existing dimension values and apply formulas to result in dynamically updating geometry.
For example, Width = (Height * 1.5) - 2.
Projecting To Sketch
Bring existing geometry or previously created sketches into a new sketch to use as a reference or as actual geometry. You'll use this constantly to speed up your workflows.
This also allows the creation of a master sketch that contains the high level geometry shapes and sizes that can then be reused across many features. Editing the master sketch modifies all the features.
Guides work in the background to make lining up sketch figures easy and visually intuitive.
Automatic Sketch Analysis
Every time you leave Sketch Mode, the sketch is analyzed for potential problems that might prevent feature creation. If issues are found, the analysis tool shows you exactly where the problems are.
Customizable snapping makes connecting figures a breeze. Set the snap distance in options to suite your preference and monitor. Snap to endpoints, midpoints, and to any point along a figure with visuals that are easy to see.
Tons Of Tools
Linear Pattern, Circular Pattern, Mirror, Offset, Fillet, Chamfer, Move, Rotate, Trim, Extend, and Intersect make quick work of otherwise tedious modeling tasks.
Smart Popup Menus
Reducing mouse travel and seeing the right tools at the right time is key to efficiency. Smart menus speed up the most common sketch tasks by showing tools relevant to the selection right at the mouse.
Color Coded Issues
Creating fully defined sketches that have no degrees of freedom is a best practice, but it can be hard to know when you've achieved it. Color coded sketching shows you sketch-wide issues at a glance, simplifying the issue discovery process. When everything is fully defined, the sketch is done.
Use images as a visual reference while sketching. Set images to a known real-world size using the Calibration tool. Sketch on top of them to trace objects so they can be reproduced.
Use Tracing Images for reverse engineering or creative work.