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Lofting problems max/gmax

Willem

Willem

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206
Country
netherlands
Hi all,
i joined Fsdev a while ago, but never posted here before.
Not really a novice (i released an f27 a few years ago and have been working on an AN72 for ages. I now am trying to create a new version of the F27), but i just cannot seem to get decent results with lofting.
I'm trying to create a vertical stabilizer tip using the lofting method:
In side view i created a path line.
In top view i selected the appropriate edges of the stabilizer and created a shape from them.

tip.jpg

(ignore the green line, it is from a backdrop polygon)

I cannot for the life of me get a decent loft out of this, i tried all sorts of things from adjusting the pivots of the shape and path (both in local and in view mode) to adjusting the first vertices of both shapes.
For some reason always the orientation is off, the loft is jumping in all sorts of directions and positions or the normals are screwed up.

So i tried to go back to the basics and drew two simple shapes and experimented with that. I got a kind of okay loft out of that but the loft still lies a lot of distance above the shape...
Also i am unable to change the orientation of the shape on the path in the loft, it just seems that i am missing the obvious here...
Been at it for two nights now, so i'm getting kind of desperate here.:mad:

Can someone please explain how to create a decent loft and how to use the pivots etc??
I did find an old post over at ffds which referred to this tutorial:
http://www.cgarchitect.com/upclose/article2_TB.asp

There is mention of pivots and their relation to a loft:
"The orientation of the shape on the path is a bit more complex. I'll talk you through it here and show an example, then discuss it in more detail later. The local Z axis of the shape aligns itself "down" the path and the local Y axis of the shape aligns with the local Z axis of the path."

But i don't really understand what he means by this, and there is no discussion in more detail to be found further on in the tutorial.
Of course i experimented with all sorts of pivot positions and orientations but i just cannot get a finger behind the principle of all this.

Also i still had an old pdf tutorial from the late Gerard vd Harst on creating a wing in Gmax, but following those steps in my model did not result in success.

Hopefully someone can help me :confused:...:wizard:
 
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Hey Willem,

We recently had a big Lofting 'event' with finding some tutorials on YouTube on how its done. Try here; http://www.fsdeveloper.com/forum/showthread.php?t=21924

As for getting a loft to make that wingtip, which is wide at one end, and pointed at the other, I doubt Loft is the avenue of choice for that. You cannot really get it to pinch, though you could with Taper, but only after you create a Loft and you will probably spend more time on it then needed.

The way the great Gerard would do it, is create a 'Line' and then adjust it into a visible tube mesh (click Visible) and set the diameter of the tube, then make sure it goes to the right locations (top and side views), then delete the inner polygons and then 'Attach' and build out the polygons connecting them from the wing surface to the tube outer edge.

That, at least for me, is the quickest way I know of.

One thing you could do with Lofting on that wingtip is to create a 'edge' only, (the rounded lip edge that goes around the circumference of the wingtip) and then build out from the wing's surface to the Loft lip.


You'll find in that first tutorial on YouTube how to modify the shape angle and size, which I didnt know you could do. Pretty good tutorials....
 
FWIW I recently found that I could not get a loft using a spline extracted from an edge shape.

Don't know if the logic gets thrown out, but some splines won't loft properly, in my experience.
 
hcornea said:
FWIW I recently found that I could not get a loft using a spline extracted from an edge shape.

Don't know if the logic gets thrown out, but some splines won't loft properly, in my experience.
Click to expand...


That was also my issue, but when I found that one tutorial on that link up above, the first tutorial at YouTube, I found that I could then move and scale the 'shape' object and thats when Lofting really opened up for me. Its pretty flexible. Adding in a modifier (which I never really do, ever) also really opens up options for what you can do with a shape 'in the middle of a Loft process'.
 
Hello Willem,

Lofts nearly drove me to despair, but until I can chuck some screenshots together here's a link to some updated material by Gerard.

Gerard's low-poly tutorial

The post in that thread you want is on post 11, but beware of Mathias's correction in post 20

Thanks again to Mathias for preserving this classic material!
 
I found that lofting occasionally worked/did not work as expected depending on the active viewport window. Possibly worth trying out.
 
Once you make a few parts with it, Lofting becomes alot more easier.

Just have to get your hands dirty and see how far it can go in making some wierd parts. Each tool though has its 'area' of need or capability.
 
Oh man...
Finally i had success!!
I did it the dirty way, i found out that from Gerard's wing tutorial i could create a loft the way it was meant to be.
The only thing different from my setup was that the stabilizer is orientated in another way. (indeed it seems that the active view has something to do with it)
So i rotated the stabilizer 90 degrees so that it was in a "flat" position like a wing would be.
I then created the shape and the path again, with the stabilizer in that corrected position.
Now the loft worked, though it was still rotated by 90 degrees about the path and the normals were incorrect, but it was stuck to the path and not dangling above it.

After the loft is made, click on the modify tab and there you can use the Twist function (under Deformations), i dragged the graph to 90 degrees and there it was in the correct position, the loft rotated 90 degrees in the correct direction.
As for the normals, under Skin Parameters it is just a matter of checking the box at Flip Normals.

Then it was a matter of altering the shape of the tip to conform to the profile of the stabilizer. This can be done under Deformations, using the Scale function. The graph that opens controls the scale of the loft. Just drag the most right control point to 0 and the loft is tapered to zero thickness.
It is possible to insert additional control points on the curve, right clicking on the control point and setting it to bezier smooth or bezier corner makes sure that the deformation of the loft ends up nice and smooth.
Of course you can drag the bezier handles to control the tension and direction of the bezier.

After that i rotated the whole lot back into the vertical position and all that is now left to do is filling the gaps.

stab_tip.jpg


Those tutorials on youtube are also gold man!
I never knew you could insert different shapes in a loft.

Oh and many many many thanks for that link to that old low poly aircraft modelling tutorial from Gerard!!!:eek:
Been searching high and low for that, all i could end up with was an incomplete website from the internet archives website with no images.
Excellent stuff in that tutorial!!!

Thanks a lot guys!! :):)

grt
Willem
 
Congratulations! Those tutorials are truly a God send!

I needed to create a moulded plastic door frame a few months ago and had a tough time because of not having practiced lofting in quite awhile.

I selected the "edges" of the existing door cutout, create a Spline Object from them, and then drew a lovely Shape...

...after lofting the Shape along the line, the silly thing was backwards (facing outwards instead of inwards)...

It took me quite a long time to "remember" to use the Deformation modifiers to fix my problem. :scratchch

Boy, did I feel like a dimwit when it finally "clicked!" :rotfl:
 
That is BRILLIANT! I never knew you could create such a tear drop wingtip with Lofting. Twist did that??? Nice..

Gerard was an amazing modeler. The entire time he was chatting with us, sharing his talent, he was in pain with a rare desease, bed stricken most of the time. A great loss when he went away on his next journey.
 
Actually the teardrop shape you can make by using the Scale function under the tab Deformations and adding control points to the graph where needed and drag them as needed. Also remember that you can change the type of control point to bezier smooth, bezier corner or corner for the best smooth result by right clicking on the control point.

With Twist you can rotate the loft around the path.

grt
Willem
 
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