ART.01: ESTRUCTURA DE SEGURIDAD

Width A larger than Width B, which is larger than Width C.

Save this model as House.skp.

This form will be used to explore three ways to make a uniformly sloped roof:

Method 1: Set Slope and Double

Constraints

This method is probably not what you’d use to actually solve this problem, since it’s complex and there is an easier tool to use (Follow Me). But it’s a great way to practice using double constraints.

1. On the house form, draw the two valley lines and three ridge lines. The following references points will be used:

The slope we want to use for all roofs is 8:12. The

slope, we need to first create an 8:12 construction line along a face that is perpendicular to H-E. Since Face A is perpendicular to H-E, it will be used to create the construction line. The construction line will then be moved to an appropriate location for raising the roof ridge into place.

2. Use Protractor to draw a construction line starting at Point C. Align the protractor with Face A and align the reference line along C-F.

3. Use the cursor to indicate the direction of the roof angle (above, not below, line C-F), and type 8:12; this ratio is automatically entered in the VCB. Press Enter to create the construction line.

Because the ridge lines will be moved upward using Point E, the construction line needs to be positioned correctly.

4. Move the construction line in the red direction from Point D, to the point where it intersects Line B-E. This is so the slope of the roof will be aligned properly with the center section of the house.

5. Select all three ridge lines and move them up by Point E until it meets the construction line.

6. Because the construction line is no longer needed, right-click it and select Erase.

7. Since we’ll want to refer back to this state of the model later, save the file as

RoofIntersections_before.skp.

8. Because it’s a good rule of thumb to save your model after every few steps, make another copy of this file, which you will continue working in, called

RoofIntersections.skp.

Now the main section’s roof has an 8:12 pitch. The other two roofs, however, have different slopes. We’ll start fixing this by focusing first on the wider, perpendicular wing.

9. Draw an 8:12 construction line on Face B, from either Point A or Point C. The current pitch is too flat, so fill in the missing material.

10. Push/Pull this chevron face back to the valley intersection with the main roof (Point D).

11. Now spin the house around so that you can see the intersection area that needs to be resolved. The lower point on the chevron apex needs to be moved, but you can’t move it as long as the chevron is a single face. Therefore, divide the chevron by drawing a vertical line at the apex.

12. Use Move to drag the lower middle chevron point to Point E.

14. The last (upper) chevron point needs a double constraint to move into the proper position. Start dragging this point along its ridge line (along an axis) and Shift-lock this direction.

15. Keep pressing Shift. Because it is the rear face of the center roof (Face D) that will be extended to connect with the modified (higher) roof, place your cursor anywhere on this face. When the line-face constraint appears, click to relocate the chevron point. This will place the point at the correct location along the ridge line to generate the same 8:12 slope as Face D.

16. Clean up the rear face by deleting the extra line.

17. Now the slope on the interior corner needs to be readjusted. To do this, you need to create a valley line from Point D that lies at the correct angle on the center roof. So draw a line from Point D that is constrained to Face E. Press Shift to lock this constraint.

18. Now place the cursor anywhere along the center ridge line. Use this double constraint to create the new valley line.

19. To complete this corner, draw the line shown.

21. Now swing around to face the front of the diagonal wing. Create another 8:12 construction line on this face. This time the roof is too steep. Draw another chevron shape as before, which will be used to remove material from the roof.

22. Push/Pull the chevron face back to the valley line of the center roof (Point I). You can’t go any further than this point. As before, draw a vertical line at the chevron apex.

23. Move the top point of the chevron apex to Point H.

The lower apex point also needs to be moved, and needs to be constrained along the diagonal roof ridge line. This point can be moved freely along the ridge line, but the ridge line can’t be used for a double constraint because it is not parallel to any axis. 24. Therefore, create a construction line along this ridge.

25. Drag the chevron point along the ridge line, locking it to the construction line. Constrain this point to Face D.

26. Erase the extra line on Face D, as well as the construction line. Now the triangular face at the exterior corner is the only one whose slope is not 8:12.

27. Orbit to face this area. Move the top triangle point so that it is constrained to the center roof ridge line (in the red direction), press Shift . . .

28. . . . and constrain to Face F as well., to match its slope.

29. Erase all extra lines at this corner. Now all three roofs have the same slope. Be sure to save the file

(RoofIntersections.skp), because you will use it

later.