How to create multiple curves ending in multiple points?

Hello all

Hello, I try to redo this: https://www.reddit.com/r/blender/comments/v3dfyb/as_requested_heres_a_little_tutorialbreakdown_of/
the redditer won the day on r/blender!

I cant create these curves between the origin and the multiple points. This is the start to center step in the video.

I tried to set an arc as base curve, the position input does not plug into the end position of a curve. I guess this is a fields thing, a field of vectors on one side and single vector on the other.

I am not so familiar with the field concept and often stuck on this kind of issue on multiple objects.

I would try first to set the start point of the instanced curves at the center of the effect.
That should give you something straight and ugly. But then you can convert this curve to a spline rather than a poly curve. And then use the handles to give it an arc.

In some ways this is close to that :

Good luck and if you’re still stuck post a .blend so we can look into it.
The technique is quite clever , once you get the basic idea it looks simple to redo.

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Hello, thank you for your answer.

Although it is an interesting tutorial and it has taught me things, it does not answer my initial question. It is basically the equivalent of an extrusion along the curve on multiple points from a star primitive.

I’m still stuck at the same point. Which is that instances will behave locally relative to their instancing object. Curves like curve line with two vectors as input will not accept global positions, because it’s a different field. Maybe vector math could fix that, so far not.

I understand that I am not on the right approach, or I am ignoring something key.

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Hum, it’s hard to give you pointers without knowing the specifics about what you’re doing.
If not, that would mean I should recreate the setup as a example and share the .blend file with you.
In the end I’m just guessing here but it’s limited …

You need an object like an empty that will be the center position.
Then you need to realize instances on all the curves.
From there it should be possible to take one point of all these curves ( start or end) and set their location to the empty location. Is it something that you can do ?

Then you’ll have something working, but you should make it prettier, and then you can apply the logic from the tutorial to do that.

Feel free to share a .blend; that will be simpler to see if something is wrong, and or provide solutions !

I think the question may already have been raised here:

Thank you, indeed this is what I was looking for: the Endpoint Selection node make possible to set a global position on an instanced curve end point.

Not sure how and why this node exists, it is pretty obscure since I barely know the underlying logic of it.

@sozap, thank you too, you point the realize instance node that I missed at first.

Since I am not trying to mimic the mimic, i’ll eventually post a file and some pictures about it. I try to make something like the arcs of fluid matter at the surface of a sun, some of them being repulsed by a force field.

Cool !
It may be tempting to start learning geometry nodes with a simple practical goal like you do, but that can be a bit overwhelming and it may not be the simplest way to understand the system.
The best is to do simple, boring stuff that only involve a few nodes and concentrate on one or two functionality. Without a particular goal in mind. And at some point you’ll be ready to do much more complex stuff.

What is a bit different from shading and compositing nodes here, is that many nodes works in context.
You have a position node, depending on where it’s plugged it doesn’t represent the same thing.

The end point selection node works that way too.

The blender manual seems well written : https://docs.blender.org/manual/en/latest/modeling/geometry_nodes/fields.html

That and a few basic tutorials should get you started quicker and once you get the logic it will be much more simple.

Thanks but I am quite experienced… I was doing similar things with Softimage 10 years ago. I am confused sometimes with geometry nodes, very familiar sometimes , and sometimes not. There was nodes like “if” or “switch context”, i wish they were here. Also I started geo nodes before 3.0, adding more confusion on top of it.

Anyway it’s quite unpleasant to be taken for a beginner, but ok i guess. I hardly read docs until it comes necessary so it must be it.

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Hey !

It’s possible to do conditional statement with the compare node and switch node. I don’t know ICE so it may be a bit different. Because GN use very minimalist building blocks, you’ll have to add other nodes to complete the condition.

And, sorry if what I said felt condescending !
I see a lot of people asking questions here and I find that they start learning GN with a goal in mind without taking time to really learn the basics of how it works. That sound quite difficult to me.
Then of course they quickly get stuck with basic issues, leading me to the same generic answer.

If you’ve got a lot of prior experience with similar systems you should know better than me how to learn them and find your way into them. Some tools are intuitive and you can count on prior experience to find your way without going back to basics, some others don’t work that way.

Before GN I did a lot of scripting and that helped me a lot in the long run, but still I had to start over from the basics, because it’s a different system with different rules of the game. You can start playing the game and guess the rules by trial and errors. Or just learn them before starting to play, it’s kind of boring but that may help you to get faster to the point.

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