Creating Surfaces from three or more points.

robert_melascaglia

Greetings all

I have solid geometry and I like to select four points to create another surface area.  How does one go about this, thanks.

Robert

konstantin_shiriazdanov

Hi, try to make closed contour by using briging curve or spline through a number of points and then use Fill feature

billy2

like @konstantin_shiriazdanov says and try to figure out some curves. The problem will be position & direction. Direction will be the most difficult.

Here's some steps to take. It's a little winded, but there's a concept that needs to be had.

Below I have 4 random points in space:


From here I create 2 vectors (bridge curves) defined from 3 points:

One thing to note about creating curves with points, direction ain't possible:


Let's move on, there's an answer at the end. Create a plane from 2 vectors using sweep:


Remember a sweep with 2 linear curves produces a plane that I can sketch on. 

I create a sketch and another vector in the sketch:


Now I have direction defined in a sketch:


I can drag the direction around in the sketch giving me the control I want:




This is a long winded answer to your question and I'm trying to illustrate a concept used in surfacing. Sometimes you have to build a surface to build another surface. It's like chess and requires thinking 1 or 2 moves ahead. Worry about direction and your constructs based on direction vs. worrying about position. Position's easy.

Don't try and build a surface from points   vs.   try and build the constructs that are going to control and build your surface.

Don't freak out, when I'm designing, it take minutes to build my surface constructs. I blast through it.

It's a 2 step process: build the surfaces to build a surface.

 

michael_mcclain

@billy2 creating a surface from another surface as you showed is something I hadn't considered. I dont use intense surfacing very often but the explanations of position and direction are very useful when planning how to make curves and surfaces.

On a side note, couldn't you use a three point plane instead of the swept surface? I understand this was for illustration purposes, but I'm wondering if there is a specific reason I'm not aware of.

billy2

I'm not not a plane or axis type guy. I don't make friends during a plane & axis conversation.

There's so many ways to describe a plane, any will do. A plane is just a point & vector. If you want to control the "x" direction, then it's 2 vectors. With sweep the "x" direction is defined by picking sweep & path, the curve you pick 1st is typically defining the "x" direction and you need to figure out how they're  doing it. In my case, I don't care which way horizontal & vertical are oriented as I'm not aligning to 'x' in any down stream operations. Sketch direction in this example isn't important.

There was a time when the thought was the world should be thought of as points & vectors. Then someone thought up a boundary representation. 

Solid modeling and those 3 planes has simplified things so much, we've forgotten about position & direction. It's old school, it's cool.

To me surfacing is easier than solids and the controls you get allows you to build anything.

michael_mcclain

That some interesting insight. I will have to play around with some examples to see how it can be applied to my modeling style.

billy2

So here's how the plane & axis conversation goes for me.....

I have a lot of SW files inside OS and none of the datums came over through the translations: IGES, STEP or Parasolids. I have the geometry and no datums. I've lost the design intent. Where's the project skeleton? I'm only getting half the puzzle pieces from SW and those who use planes & axis. Had they used curves, edges & surfaces. Guess what pops up in a translation? I get everything if you use surfaces.   

I use analytic surfaces in my OS designs and when they go back to SW, everything is there. The data returning to SW is better than the data I received from SW.

billy2

@michael_mcclain there was guy at SW world a long time ago who gave a curvy 101 lecture. He said the best time to learn surfacing is a Saturday morning with a warm cup of coffee. The time not to learn surfaces is when you have to get something done. I agree with his statement. Start breaking things down to a position and a direction from that position. 

robert_melascaglia

Billy2 - Agree without a doubt.

robert_melascaglia

Billy2  - thanks for the detailed example; will no doubt try your examples in a test case.  However, sure I will learn more about surface modeling, thanks.