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Edges and Surfaces

SU Fundamentals 2-1 Edges and Surfaces

0:03 In the world of SketchUp, no matter if you have a simple or complicated model, underneath it all are only two types of entities: Edges and Surfaces.

0:17 The most common procedure you will use in Sketchup is to create a surface with the drawing tools and pull that surface into 3D.

0:28 This is why the core concepts of SketchUp really come down to the line tool and understanding how edges and surfaces behave...

0:39 ...so you can create any shape and draw in any direction that you want.

0:48 Let's practice drawing on a simple rectangle to understand some of the most important concepts within SketchUp.

0:58 Open the example file we've provided for this course.

1:02 Across the top are several tabs related to the exercises. Click on the first tab and let's get started.

1:09 Choose the line tool and find the midpoint inference on one edge. It looks like a cyan dot.

1:17 Draw a line from here, across to the opposite mid-point.

1:23 Now draw another edge, crossing the first, again from mid-point to mid-point.

1:28 Do this again, several times, drawing lines from midpoint to midpoint, that divide this larger surface into multiple smaller surfaces.

1:40 If at any point you accidentally draw an edge too far or to the wrong point, don't worry, simply go to the Edit menu and choose: Undo.

1:52 You can undo as many steps as you need and then redraw those edges until our original surface is divided up into 16 smaller rectangles. in this very

2:04 In this very simple example we can learn a lot about SketchUp geometry.

2:11 Use the selection arrow to click around and select various surfaces and edges.

2:17 Notice that even though we were drawing edges across the full width of the rectangle,

2:24 any overlapping edges automatically break other edges as well as the surface itself.

2:32 Now choose the eraser tool and look at the icon. It has a small circle on the near corner.

2:40 Use this point to click on several edges and watch what happens. When the edge dividing two surfaces is erased those surfaces merge.

2:50 This is an essential concept, that you can divide or combine adjacent surfaces into more complex shapes.

2:60 There are two important factors to making this work.

3:03 One is that there must be a complete loop of edges to define a surface.

3:08 If we erase one of the outside edges, that breaks the edge loop and the surface is deleted.

3:15 However, we can recreate the surface by drawing the edge back in and thus completing the loop. The second important factor is that

3:23 The 2nd important factor is that all of the edges must be coplanar, which is to say that they must be completely flat along an imaginary plane.

3:34 Our rectangle is completely flat, so we can easily divide or merge these surfaces.

3:41 To see an example of non-coplanar edges click on the second scene tab.

3:47 Here are three sets of edges and let's draw a line between the endpoints to see if we can create a surface.

3:54 The first example works fine. All the edges are parallel with the red and green axis so they are naturally co-planar.

4:01 The 2nd example also works which shows that the edges don't have to be parallel with the axis as long as they are still co-planar.

4:11 The 3rd example does not create a surface and we can see why. These edges are not on a flat plane, they are not co-planar.

4:22 The main point to take away from this example is not to worry about drawing on or off axis.

4:29 In fact you will almost always start by drawing shapes and lines on the axis and then you'll move and rotate those shapes off the axis as needed.

4:38 The main point is to realize if you draw a closed loop of edges and it does not create a surface...

4:45 ...then it's likely those edges are not coplanar and you'll need to fix or redraw your shape to create a surface.

4:53 For now, click back on the 1st scene tab and let's explore a few more important concepts within SketchUp.

5:03 As we've already done, use the eraser tool to click on edges and erase them one by one.

5:11 However, there is a faster way to erase these edges.

5:14 Instead of clicking on edges, hold the mouse button down and drag the cursor over several edges.

5:22 They become highlighted as you drag over them and when you release the mouse button they will all be erased.

5:29 Use this method to highlight and erase all the interior edges.

5:34 Remember, you can undo if you erase an exterior edge but let's get back to our original rectangle.

5:42 We are going to draw the same edges as before but as we just saw with the eraser tool many tools in SketchUp can be used by clicking your mouse or by dragging it.

5:54 Draw the edges again from midpoint to midpoint and this time be very careful to click once each time to start and to finish each edge.

6:07 The eraser is one of only a few exceptions where it's better to drag your mouse button.

6:14 Actually, most tools in SketchUp work best when you single click to start them and to finish them.

6:22 Remember: click, move, click.

6:27 After drawing in the edges again, let's focus on a new concept within SketchUp.

6:34 You've already seen how drawing from or to an edge divides that edge,

6:40 did you also notice that when you erase a divided edge it not only heals two surfaces together it also heals the divided edges together.

6:50 When we erase this series of edges to create a larger surface we are joining edges back together.

6:58 What do you suppose will happen if we simply draw a new edge over an existing edge?

7:04 In some software this results in two overlapping edges, but in SketchUp this only results in breaking the original edge.

7:13 You can see we now have three edge segments instead of the one.

7:19 This may or may not be what you intended so be careful when drawing over existing edges.

7:26 At this point you also know how to join these broken edges back together

7:32 We simply need to draw an edge from one endpoint, even out into open space, then hit the ESC key to stop the line tool from drawing additional edges.

7:43 Now we have a dividing edge and as we just learned we should be able to erase this edge and heal the divided edge.

7:57 You may be wondering at this point how to erase just a surface.

8:02 We can erase edges which may also erase the surface but what if we just wanted to delete the surface alone?

8:09 To do this we simply select the surface with a selection arrow and then press 'Delete' on your keyboard.

8:17 Once you have deleted a surface, to get it back we simply need to trace over one of the edges that help form the surface.

8:24 Make sure to draw from endpoint to endpoint, or as we just learned you will also split the edge you are tracing.

8:32 By tracing an edge we can tell Sketchup to recreate the surface.

8:38 We are now ready to move onto other examples.

8:42 If you'd like, take some time and practice what we've just learned.

8:47 Draw additional edges to further divide this rectangle just make sure that you are always drawing from edges or endpoints.

8:56 Use the eraser tool and try to come up with some interesting shapes. We'll see you in the next lesson.