[Below is a sample from the second part of the tutorial]

We're going to create two contrasting variants based on the same initial model. These concepts will be somewhat more refined than the first model, with a bit more detail and attention to surface quality.

(Sample videos are hosted on YouTube. Videos in the actual tutorial are, of course, larger and sharper. For full-quality video you can download a more extensive "demo CD" here)


5. Begin by moving the first column of points of the side window surface out by 3.4 inches.

6. Angle the side greenhouse surface in with Shear. Select the lower front End of the surface for the Origin Point, pick an arbitrary point straight up for the Reference Point, and specify an Angle of 15 degrees.

Origin Point
End Snap

7. Move the whole surface out by 3 inches.

8. Use MergeEdge to combine the pieces of the top edge of the side surface. The split edge either won't be used in this iteration, or will have to be moved anyway.

9. MatchSrf the roof back up to the side surface. Specify Position continuity and use the Match Edges by Closest Points option. This will need more tweaking, but we'll look at other areas first.

In this phase we're going to pay more attention to surface quality issues. Examining the top greenhouse surface with Zebra and CurvatureAnalysis shows some tight curvature around the side surface. That will have to be dealt with, after doing some work on the nose.


10. Move two points on the fender out by 1.4 units. The crease is going to be moved out and slightly straightened.


11. Move the top point out 1.1 units.

Zebra analysis shows the side fender surface flattening out a bit right at the front.


12. Move the second point in the first column up by 2 inches and out 0.7 inches.


13. Move the top point in the 5th column out by 0.6 inches.


14. On the 6th and 7th columns, move their top points out by 0.3 units.

15. ChangeDegree the side surface to 3 from 2 along it's height.


16. Move these 4 points in by 1 inch


17. Draw a Curve in the Right view redefining the character line(because it's simpler to explain than editing the original.)

18. Trim off the side surface with the previous curve. It is convenient for editing to keep edges untrimmed, but trimming allows you to modify that edge without adding excess control points to the surface, which is also good for point-editing.

19. MatchSrf the upper nose surface to the side surface. Specify Position Continuity and Match edges by closest points. Leave the other options unchecked.

Without using the Refine option, there are small visible gaps between the surfaces, but we'll 'nail those down' after refining the overall shape.


20. Align and place these 2 points in the first row using SetPt. Specify Set X and Set Y, Align to CPlane, and type the coordinates with the Right view active.

21. Delete the small front surface.

22. ExtrudeCrv the edge of the top nose surface down by 7 inches. By default the edge won't be extruded straight down, that's adequate for now.

End Snap

23. Split the upper nose surface with the Isocurve option and Shrink set to Yes. Snap to the corner of the trimmed edge with the End snap.

24. UnTrim both pieces of the split surface.


25. Move three points on the new top fender surface out 2 inches and down by 1 inch.

26. Move the inner front point in by 1 inch and back 0.1 inches.


27. Give the fender a hint of compound curvature by moving these two points up by 1 unit and out by 1.

28. ChangeDegree the fender surface to 3 along it's width.

29. MatchSrf the upper fender surface to the front surface. Specify Position Continuity and use Match edges by closest points.

30. MatchSrf the upper front nose surface to the upper fender surface, just for now. Specify Position Continuity and use Match edges by closest points.

Now to begin figuring out how the nose, windshield, and A-pillar are all going to come together.


31. Draw a Curve in the Front view.

32. From the Front view, Project the curve onto the top greenhouse surface.

33. Rebuild the projected curve. Specify a Point Count of 7, a Degree of 5, and Delete Input.

It's important to remember that Rebuild doesn't 'care' about maintaining the direction of a curve or surface at it's ends.

34. Use SetPt to align the second point from the centre to the first point. Specify Set X and Set Y, Align to CPlane, then snap to the End of the curve in the Right view.


35. Since it would be hard to edit, just Delete the nose vent surface made in the first phase.

36. Use ExtrudeCrv in the AlongCurve Mode to build a new surface. For the Curve to extrude, pick the curve on the windshield, and for the path curve pick the centerline curve used for the original vent surface. The surface is built as if the path curve was aligned with the curve to extrude.

Curve to Extrude
Path Curve

Looking at the model under Zebra striping, the top greenhouse/windshield surface seems to be just a little too flat right at the front corner--or perhaps the rest of the windshield is not flat enough--and too curved along the edge further back. We could point-edit this, but in the context of a tutorial it's simpler to reconstruct the sweep, the surface has a large number of control points and many would have to be very finely tweaked.

End Snap

37. Turn on the control points for the curve used for the section of the initial greenhouse surface. Move the outer point, snapping to the End of the side greenhouse surface.


38. Move the next point from the outer end out by 1.5 units and forward by 0.7. The CurvatureGraph tool was used to figure out how much to move it--the goal is to make the curvature at the outside equal or more curved than the centre.


39. Move the inner two points back slightly, by 0.2 inches.

40. Use DupEdge to extract a curve from the back edge of the greenhouse.


41. Move the second point from the outside in by 1.0 units, back by 1.82 units and down by 1.32.


42. Move the second point from the inside out by 0.3 units.


43. In the Right view draw a Section curve through the top greenhouse surface. This was done instead of using ExtractIsocurve just because it's simpler to place a section at a precise location.

44. Rebuild the section curve. Specify a Point Count of 4, a Degree of 3, and Delete Input.

End snap

45. As we did earlier, use SetPt to align the second point with the end point to restore the tangency.

46. Move the middle points out by 1.8 inches.

47. Move these three points down by 0.3 inches.


48. Move the third point down by another 0.4 units.

49. Delete the original greenhouse surface.

50. ExtrudeCrv the curve drawn at the centerline of the greenhouse a few units. Even though all the section curves are perpendicular to the centerline, this is still necessary to make sure the surface will mirror smoothly.

51. Build a new surface with Sweep2. Do not specify any cross-section curve options and set Tangency continuity to the centerline edge.

Section curve
Section curve
Section curve

Two of the section curves for this surface were edited so that they did not touch the rail curve. You can see how this affects the resulting surface. [End of sample section, return to Hydraulic Design.]