1. Curvy Stuff 102 4 - Continuity and Lofts
Edward Eaton Product Design Services Aurora, Illinois
Curvy Stuff 102
4 - Continuity and Lofts

2. Continuity C0 – Contact Continuity C1 – Tangent Continuity
C2 – Tangent and Curvature continuity

3. Why should I care? C0 – harsh, unappealing
C1 – abrupt blend, optical illusion of concavity
C0 – harsh, unappealing
C2 – smooth blend,
visually appealing

4. Why should I care? Curvature plot Stress points No stress points
Smoother objects require less material
5.75
5.47
5.41
Curvature plot
No stress points

5. Continuity ALONG loft Here’s a profile Profiles set up for loft
Loft algorithm connects profiles with a spline based skin
Each segment in profile makes a sheet (is its own loft!)
Profiles set up for loft
Here’s a profile
Loft profiles together

6. Continuity ALONG loft
#Sheets = max # of segments in any of the contributing profiles
5 sheets

7. Continuity ALONG loft Sheets usually make algorithmic (C2) faces
Where possible, sheets will try to be planar
Sheets usually make algorithmic (C2) faces

8. Continuity ACROSS loft
An algorithm sometimes forces C1 continuity between sheets
Lofts are C2 continuous along each sheet, but not between
Lofts are only C0 continuous across sheets

9. Continuity ACROSS loft
Maintain Tangency
Forces non-analytical sheets into single C2 sheet based on sketch tangency
Change profile so planar sheet can’t exist

10. Continuity ACROSS loft
Maintain Tangency is not a great solution
Only way to guarantee quality continuity across loft is to do it manually
Ugly
Will work when ellipse split here
Will not work when ellipse is split at control point

11. Curvature Lofted faces have spline skins
Controlling lofts requires understanding splines

12. Splines & lofts – section planes
Design intent
Could have predicted this with sketch
Even section spacing
Lofts always connect sections with spline based skin!
Loft planes through spline points
Need 5 sections to match
Attach sections to curve
Need 12 sections to match

13. Splines & lofts – adding sections
Design intent
Loft is as predicted
insert section

14. Why should I care?
Use sketch splines to predict and diagnose lofting problems

15. Splines & lofts Concept: Why should I care?
Spline points in straight line
Why should I care?
Lofts can follow straight lines
without guide curves

16. Splines & lofts Concept: Why should I care?
Spline point moved a little
Loft gets wiggles
Why should I care?
Minor variations send shockwaves throughout loft

17. Ripples get clamped out
Splines & lofts
Concept:
3 points in tight grouping
Ripples get clamped out
Why should I care?
Can use tightly spaced sections to clamp wiggles

18. Splines & lofts Concept: Why should I care?
Spline broken into two tangent splines
Wiggles eliminated
Why should I care?
Break loft into sections to squash wiggle propagation

19. Splines & lofts Concept: Why should I care?
Cannot match with a spline!
Design intent is line and tangent arc
Loft fails to match too
Why should I care?
Cannot use lines and arcs to accurately lay out lofts

20. Loft achieves design intent
Splines & lofts
Concept:
Can match with two splines
Loft achieves design intent
Why should I care?
Must break up lofts at C1 changes

21. Splines & lofts I wanted a smooth lofted model
Break loft into sections to eliminate wiggles
Don’t want wiggles to effect the smooth end
Perimeter laid out in splines

22. Splines & lofts Would like end curvature to match Unfortunately…
Now forward section can match smoothly
Unfortunately…
Cut back to where curvature is as intended

23. Homework assignment Experiment heavily with splines
Experiment with tangency

24. -Disclaimer- Loft profiles are parallel
Spline evaluation is compromised by angled sections
Loft profiles are
parallel

25. -Disclaimer- Sections are all balanced
Spline evaluation is compromised by unbalanced sections
Sections are all balanced

26. -Disclaimer- Single patch follows intent
Spline evaluation is compromised by multi-section lofts
Single patch follows intent

27. Loft Guide curves
Guide curves add pressure to a loft

28. Loft Guide curves Guides need to be curvature continuous No guide
Guide curve made of tangent lines and arcs
Guides curve made of splines
No guide

29. Loft Guide curves
Pressure from guides cause loft to miss sections

30. Loft Guide curves Another loft Edit to add guide curves
Pressure from guides split the sheets
Edit to add guide curves

31. Loft Guide curves rules
Best bet is to use curves as a construction tool
Can use curves to modify loft
Design intent is preserved

32. Loft Guide curves rules
This is how sweep with guide curves works!
Loft profiles are generated automatically
Set up path (which defines planes)
Set up layout curves
Set up section

33. Loft Guide curves rules
Legitimate reasons to use guide curves
Tell profiles how to connect

34. Loft Guide curves rules
Legitimate reasons to use guide curves
Control edges

35. Guide curve trick
All lofts have guide curve…

36. Guide curve trick
Loft guide curve trick…

37. Guide curve trick
This ‘pick’ guide curve is problem on closed sections

38. Guide curve trick
Here’s the workaround

39. Loft Guide curves rules
Do not use to model transition region (unless you don’t really care about quality)
One guide can be used successfully on lofts made up of closed contours

40. End of Continuity, curvature, and lofts
Onto Awful modeling challenges