Designing in SketchUp

      Avis: SketchUp 2015 est ici ! Quand vous regardez cet article Knowledge Center, soyez sûr de sélectionner « SketchUp 2015 » de la zone rouge ci-dessus pour voir la version 2015 de ce contenu. S'il n'y a aucun sélecteur de version, ce contenu s'applique à toutes les versions de SketchUp.

< Concepts Guide | Drawing Quickly >

SketchUp models are fundamentally created by joining lines as the edges of the model. Faces are automatically created when any three or more lines or edges are in the same plane (an infinite flat 2D space), or coplanar,and form a closed loop. These edge and face combinations are combined to create 3D models. The following image shows three unconnected coplanar lines. These lines were drawn with the Line tool (this tool looks like a pencil).

The following image shows four connected coplanar lines and the subsequently created flat, 2 dimensional, face.




Note: Everything you draw in SketchUp is generically referred to as geometry.


To create a 3D model, simply draw up or down in the blue direction (parallel to the blue axes). The coordinate system (axes) is covered later in this section. The following image shows the first line created in 3D space.

As you continue to draw lines, following the colored axes, faces are created. The following image shows four faces created simply by drawing lines parallel to the three axes directions (red, green, and blue).

There is one line left to draw to finish a 3 dimensional box. Notice that when this one line is drawn in, two faces are created (the top and front faces).

You can do a lot in SketchUp simply by drawing lines to form faces using the Line tool. And, you can draw lines starting anywhere (on another line, on a face, at a point, and so on). Can you recognize the previous 3D box within the model of the following house?

Look around the room you are in. Notice how everything you look at has faces. Some faces might be rounded, some might be flat. Additionally, everything has edges that bound the face, such as the edge of a shelf in a bookshelf.

Note: SketchUp is not the same as Computer Assisted Design or CAD. CAD applications are designed specifically for representing concrete information, while SketchUp is for exploration and design of concepts and ideas (though you are not prohibited from designing models that are as concrete or accurate as those designed in CAD).



SketchUp files can be imported into several different CAD applications for further processing and several different CAD files can be imported into SketchUp to quickly create 3D models.

Introduction to entities

As mentioned previously, lines are combined to create faces in SketchUp. Lines (also called edges) and faces, are just two of the many building blocks (called entities) used for creating models in SketchUp. A full list of SketchUp entities follows.


Name

Notes

Line

Lines in SketchUp are straight. Lines, also referred to as edges, are the most basic building block for all SketchUp models.

Face

Faces are created automatically when three or more coplanar edges form a closed loop. Faces have a front side and a back side. SketchUp attempts to put the front side of all faces on the outside (facing out) of all of your models, though sometime you might have to tell SketchUp the direction for your faces.

Circle

Circle, arcs, and curves are comprised of several lines or edges.

Arc

Polygon

Curve

Polyline

Group

Group entities are used to combine two or more entities in your model for quick operations such as a copy.

Component

Component entities are like groups but can be reused in all of your SketchUp models. Components are just SketchUp models used within other SketchUp models.

Guide Line

AGuide Line entity is a temporary line used as a drawing guide.

Dimension

A notation indicating length of an edge or a radius.

Surface

Surface entities are the result of combining a number of faces to give the impression of smoothness.

Section Plane

Image

An imported raster, or pixel-based, image.

Text

Text can be unattached (floating) or attached to a specific entity using a leader line.

The SketchUp coordinate systems

SketchUp uses a 3D coordinate system whereby points in space are identified by position along three drawing axes: plus or minus X, Y, and Z (above ground/below ground) values. In SketchUp, plus or minus X is represented by solid red and dotted red lines respectively; plus or minus Y are represented by a solid green and dotted green axis lines respectively; plus or minus Z (above and below the ground plane) are represented by solid blue and dotted blue lines respectively. The plane where the red and green axes lines lie is called the ground plane. Finally, the term origin, is used to define the place where all of axes lines start or originate.

The following image shows the drawing axes in SketchUp (the lines have been thickened to make the axes easier to read). The black circle represents the origin.

Understanding SketchUp's coordinate system is important because SketchUp's inference engine (explained next) provides you help with drawing accurately.

Following the inference engine

SketchUp has an invisible inference engine to help you draw accurate and realistic models. The inference engine locates or infers points from other points in your model, such as the center of a circle, the midpoint of a line, a line that is perpendicular to the ground plane, a point on a face, a point on an edge, and so on.

SketchUp notifies you of these points by using both color indicators and tool tips, which are on-screen messages indicating the location of the cursor as you draw an entity. For example, SketchUp displays the string 'On Face' when the cursor is touching a face. The following image contains five common inference tool tips .





Additional information on the inference engine, including inference types, is in the section of this guide.

The first step to drawing in SketchUp is to learn how to draw accurately by following the cues of the inference engine. Simply select the Line tool (it looks like a pencil in the toolbar or tool pallet ) and start drawing. Pay attention to the on-screen tool tips from the inference engine as you draw. Most everything you will create in SketchUp can be created by inference using the Line tool.

You can move on to learning how to draw quickly after you master using the inference engine.

= Functionality only available in SketchUp Pro

< Concepts Guide | Drawing Quickly >