Cineversity

Hi,

I searched tutorials but not find any where I can understand concept.

In spline and its intermediate point where and when have to change it mode and what does its effect in modeling….? Whats is the Professional way to set the spline mode and its angles…?

Anyone who can suggest a link of a tutorial….!

Greets.

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Hi Iacdxb,

The simplest way to see the effect of the intermediate points, is given with the Circle Spline Primitive. Call one up and while it is active, go to the Attribute Manager and set under Object the Angle to 90º. Now it is a square.

Why is that? The Circle is described as Primitive only by four points, anything else is based on intermediate points, which are points set by the application based on the rules are given to them. In the case above, if the direction change is create/equal to 90º, a new point would have been set (internally), but the four points inside the default (MAXON) definition is already sufficient for the 90º rule, hence the square.

These intermedia points are not visible or selectable in the Spline itself. If you make the Spline “editable”, you will have acces to those, but then the option to adjust them in the Attribute Manager is gone.

There is an option to have None, Natural, Uniform, Adaptive and Subdivided. The rules are simple, if a certain change would be in the spline, the intermedia point will be set, and this describes the degree option., which is the case in Subdivided and Adaptive. Then there is a certain distance, e.g., in the Subdivided option, what ever comes first will set a point. Natural and Uniform use a fixed number of intermediate points, but with a different set of rules. Of course there is None, which leaves only the visible points given.

Place a any Primitive-Spline or Spline object under an Extrude [NURBS] with and a “Movement” of Z = 200, and set the Display mode to anything with Lines if you like. Now adjust the Intermediate points and have a look how they change the result. I have attached an example, which I have animated, just to visualize it.

These points are more than often responsible for the results, but MoGraph (see example) use here only the default definition, not the intermediate points.

The Help Content has a written Tutorial. I have discussed this theme back in time with R8 - but I can’t find them either. There was nearly no change in the last decade, except that the Subdivided was added at one point.

I hope the example will shed some light on it. Especially with the Sweep [NURBS] these adjustments are very important.

Let me know if there is another question. I do not like to just copy and paste the Help Menu here, as you have it with a CTRL/CMD or right mouse click on the parameter instantly.

All the best

Sassi

Images [left] Help Menu Content, [right] attached scene file.

Hi Mr. sassi,

Thanks for the quick and detailed reply.

Greets.

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You’re welcome, iacdxb.

If there is anything else, I’m happy to look into it.

My best wishes

Hi, one more…. a little.

In circle spline and adaptive mode, Angle 5, subdivides are not equal and at angle 6 seems equal and at 7 not….;
what are the angles which have equal divides OR how to calculate angle to get equal divide…?

Greets,
Imran.

Good observation, Imran!

One might assume that 5º and 6º should result in something with equal distances (90º divided by 5º or 6º should get some “even” values)

Well, tiny little tolerances who becomes cascaded forward. Check the file, I set the steps to 72 Uniform and rotated one Circle a little bit. I colored these to showcase it more. can you see what I see, they are not congruent, but they should.

If you have degree as measurement, or trigger to set a new point, if it goes a little bit earlier (or later) each time, for what ever reasons, it accumulates. It is the change of the spline, not the degree from the center point of the circle, as splines can have a very free path after all, so the change of the path/spline is the measurement. OK, I would theoretically assume that the start and end point is 90º in distance, but if not, the given points (one of the four) ends the calculation for a moment and starts from there newly. So, the precision is not infinite, and if you take 5º, if each one is only a 0.05º off (18*0.05=0.9º) so roughly the last one is ~1º off. It adds each time, as the 5º measurement starts again from that new point. Which is visible. To be honest, 0.05º sounds pretty good by itself. but 18 times accumulated not so much. If then the definition of the circle has a little bit difference on the “four” poles [default points], then it might add.

For a circle, to get preciser divisions, use the Natural or Uniform should work better. For a free form spline, that might be a different story, as the given points have some influence on the intermediate points.

You ask how to get it calculated, I’m not certain as I don’t have the information how the primitive is “coded”.

I hope that helps. Perhaps if you need a second opinion—perhaps the support can tell you more perhaps.

My best wishes