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spline with delicate details

Valued Contributor
Valued Contributor
I'm not sure whether this post raises questions you've already answered me for many times previously. If so, please let me say sorry!
 
As you know, a curve from designers' hand sketch may often have some very delicate details. Such kind of of curves are sometimes be regarded as "sexy", and loss of even a small detail might make it "plain" or even ugly.
 
To repoduce a designer's hand drawing curve precisely in the model, may often lead to a dilema:
 
  • good pole structure + many segments or
  • ugly pole strucure + single segment
 
As I learnt from many of you, both the ugly pole structure and many segments would be trouble for surfacing.
 
It seems that I have no choice but to spend huge amount of time to try again and again to get a balanced segment/pole without loss of some key details. Is there any simple principle I should stick to?
 
Hope to have your suggestions. Even very few words would be appreciated!
 
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8 REPLIES

Re: spline with delicate details

Legend
Legend

I don't know a lot about spline mathematics, but for what I do, I find that when I want a smooth surface, I can always do better shaping a spline by poles instead of trying to move the actual points on the spline.

 

Another thing that is useful is to look at the curvature combs, and/or to look at the resulting surfaces in the reflection using True Shaded.

 

Here is what you started with, showing the curvature combs.

 

spline-combs.jpg

 

Here is what I get if I just play dumb and quickly sketch a spline on top of what you started with, and then shape the poles to be close to what you had. I try to keep the poles "flowing" from point to point, so that they don't jump back and forth from side to side, and I try to keep them reasonably spaced.

 

spline-by_poles-combs.jpg

Notice the arrangement and spacing of the poles.

 

If I extrude my spline and look at the resulting surface using True Shading with relfection lines, Notice the evenly spaced reflections.

spline-by_poles-reflection.jpg 

If I do the exact same thing to your original spline, notice the distinctly different look to the reflected lines.

spline-original-reflection.jpg 

What someone sees as "sexy" is in the eye of the beholder, and I can't judge your tastes. But to me, the eye of the beholder is literaly in the reflection. I think that is usually what a consumer sees when they are judging the sexiness of a product, also.

 

Re: spline with delicate details

Siemens Phenom Siemens Phenom
Siemens Phenom

So I would do this as 5 curves.

Spine for top, spline for bottom, spline for side.

Then either splines between or bridge between.

The whole shape is too much for one spline.

 

In reality would probably go to 3D before doing this whole profile.

Would create simple splines that are oversize for top, side and bottom.

These splines intersect each other crossing further

then surface.

later do blending surfaces. even trim and attach surfaces before blending.

 

Steve V

Re: spline with delicate details

Valued Contributor
Valued Contributor

Hi @MarkLawry

 

 Here is what I get if I just play dumb and quickly sketch a spline on top of what you started with, and then shape the poles to be close to what you had. I try to keep the poles "flowing" from point to point, so that they don't jump back and forth from side to side, and I try to keep them reasonably spaced.


This manul work is what I'm trying to do. I don't mind it may be very time-consuming. The problem is that, great effort in reproducing a multi-segment spline with single or less segments,  almost always results in loss of some key details, which the designer could "feel" quickly. It's really very frustrating.

 

Thank you for sharing some key points in handling and evaluating splines!

Re: spline with delicate details

Valued Contributor
Valued Contributor

Hi @StevenVickers

 

So I would do this as 5 curves.

Spine for top, spline for bottom, spline for side.

Then either splines between or bridge between.

The whole shape is too much for one spline.


I understand your solution as that I would need to settle on a multi(5+)-segment spline to keep all the necessary details intact.

 


 In reality would probably go to 3D before doing this whole profile.

Would create simple splines that are oversize for top, side and bottom.

These splines intersect each other crossing further

then surface.

later do blending surfaces. even trim and attach surfaces before blending.


Oversizing the splines and blending surfaces later --- this seems to make reproducing precisely the designer's aesthetics a much bigger challenge.

 

Thank you for your suggestions!

Re: spline with delicate details

Phenom
Phenom
@surfactant,

Keep in mind, previous discussions with you have been about general practices for creating high quality surfaces (aka Class A surfaces) and not replicating poorly constructed surfaces. You may have to abandon the general practices if the intent is 1:1 replication. In a manner of speaking, you're comparing applies to oranges when you take existing splines/surfaces and try to recreate them using the previously discussed preferred practices.

You're seeing things that should have been critiqued by the previous designer, had they truly intended to create high quality surfaces.

I agree with Steve in that a better approach at the beginning would have been to break up the surfaces into smaller patches. Now it's more work for you, but you will end up matching the original more closely and the quality of your surfaces should be better (look prettier when analysed with reflections, etc.).
-Tim

Re: spline with delicate details

Valued Contributor
Valued Contributor

Hi @TimF   Thank you for your great patience with the topic!

 

This is really not an easy job. The artists need to be satisfied, the engineers need to be satisfied ... Everybody need to be satisfied. Sleepless night after sleepless night ... Thanks again!

Re: spline with delicate details

Phenom
Phenom
@surfactant,

Quality surfacing isn't easy at all in many cases - trying to replicate surfaces and correct less than desirable geometry can be even more difficult.

I don't recall anyone giving you information that suggested this type of work would be easy but you're obviously discovering that on your own.
-Tim

Re: spline with delicate details

Valued Contributor
Valued Contributor

Hi @TimF   Maybe this is the life. No choice but to work harder. Thank you for your invaluable guidance!