Loft Node (follow curvature as option)

[zeffii]

This one is self explanatory, but before I tackle it I'd like to know if anyone had plans or has started their own Loft Node, or has objections to one.

[ly29]

I had one planed after cleaning up some older nodes and done interpolation. But going for really simple just place at vertices. Go for it.

[nortikin]

Alex preparing something interesting for us, and yes, lets take as rule to share plans for some nodes. i doing fractal node, that will make fractals by iterating something on vertices or centers of polygons or other way.

[nortikin]

generated fractal

[enzyme69]

I am waiting in anticipation on that Fractal thing, thanks Nikitron.

many incoming new nodes make Poly feels like NURBS and that is very interesting too.

I supposed to work on character generator using Sverchok. But currently playing wih Renderman also. And thinking of learning Swift.

Brain fragmented in deed.

[nortikin]

@enzyme69 , sverchok not for character modelling. it is better to usr mesh inside blender. but for me sverchok could be used to generate some animation or even interaction in future - i.e. bacteria life and virus life and behaviour with particles boids from blender - this is possible usage

[enzyme69]

Could be for generic type of procedural characters, because Edge => Skin Modifier. With weight and connection of lines with proportion and parametric, we can create: spider, centipede, bugs, insects and grasshopper and crickets.

[zeffii]

I plan to make this little friend in sverchok purely parametric

So loting needs

• donor proflie
• recipient trajectory
• scale trajectory (for scale per segment)

These features of the Node are planned, and flash infront of my eyes whenever I think about it. Perfect for flora, fauna and architecture.

[enzyme69]

Yes, same here. I know it's weird, but the reason Sverchok in Blender can do more.

Procedural Spider in Houdini. https://www.youtube.com/watch?v=2b11iiBjS9Y

[zeffii]

this is so bad -- i thought it would be humorous to share :)

https://gist.github.com/anonymous/6d1e05555353e438b262

[nortikin]

try to output only grouped vertices, than lines connection node to connect

[zeffii]

yes. will do -- does lines_connection node accept cyclic edge lists ?

[nortikin]

http://www.pasteall.org/blend/29667 cyclic only for one direction, i didn't finished lines connection node, there are many thoughts of it to make universal node.

[zeffii]

[zeffii]

yeah, mode to set cyclic in u or v would be great.

[nortikin]

will do

[zeffii]

your profile .blend shows me how I should think about fixing the Loft algorithm :) but will sleep on, let brain process over night

[zeffii]

[nortikin]

now i will upload full line connect (some to fix and to clean code left for later) try possibilities:

[nortikin]

i thinking of renaming this node to something like Connection or Geometrise

[zeffii]

or UV EdgeSurf ?

[ly29]

Line Connection is great indeed.

@zeffii How do you handle orientation of profile and rotation around curve? I always needed to determine profile normal and a orientation vector.

[zeffii]

I haven't done serious code yet.

but a few thoughts:

• It might be necessary to provide a profile normal, if the profile is not co-planar or to achieve some effect.
• Trajector may also need similar 'guiding' for the initial steps, then rotation in x,y,z are cumulative on each subsequent trajectory point

[ly29]

Sounds good, here is an old layout to illustrate the problem I had with twist. I did an old layout with normal for the profile in January sometime, updated it a bit now with interpolation and line connections which makes it simpler. Didn't solve the twisting problem. https://www.dropbox.com/s/4jbdyjqawul7mrt/updated-loft-test.blend

[ly29]

In the above case the profile normal could have been easily guessed by the software, also the rotation should be minimized, didn't figure out how to do that in a layout.

[zeffii]

yeah, the twisting is an interesting emergence, and why so prominently at that one corner?

[zeffii]

I know Three.js has some useful implementation of this : http://threejs.org/examples/#webgl_geometry_extrude_splines

I thought lofting was on that list at one point.. must have been seeing things

[ly29]

The rotation axis gotten from the cross product changes sign.

[nortikin]

if you have triangle, than you have normal - use previouse and next points i made example with snake, but it use only tangent to point

loop tools loft has the same problem - they didn't solve it correctly. no approximation or normal searching

[zeffii]

let's visualize the problem. Step 1 (n, n+1, n+2)... {0..n-2}

[nortikin]

yes. optionally it could be replaced by user defined vector normal + vector tangent (concerning current point) or even vectorized user-defined normals. such way we could let user (and us) to make loft in different ways and control over all stages

[ly29]

Two problems with that approach: If 3 points are in line or close to being in a line normal might point anywhere or have big changes for almost straight lines. And more seriously, it isn't that good an approach, as seen here that leads to more twisting than needed. We want to minimize the twisting, in general. To have minimum rotation between the vector and say (0,0,1). What I did above was to define the orientation/direction/tangent, d[i] for a point n[i] by taking d[i]=n[i+1]-n[i-1], from this we can rotate the profile using rotation_difference between profile normal and d[i], however then we need to rotate the profile around d[i] for minimize twist. I am sure there are better approaches... For this to work maybe we should allow over sampling of input and only use every nth point to actually place a profile.

And to have more control we need be able to provide rotation data for each part.

ps And of course d[0]=n[1]-n[0] and likewise for d[n]

Just for fun, my original attempt at this, page 14 in the sverchok thread: http://blenderartists.org/forum/showthread.php?272679-Addon-WIP-Sverchok-parametric-nodes-for-architects&p=2549433&viewfull=1#post2549433

[zeffii]

multi-sampling - yes! As option? not all lofts will need twists n crazy turns

[nortikin]

that is it