I learned the other post how to use Fixed Curve Tool with Intersect XY Tool to be able to create a pattern suitable for sewing.
I mean You have said Control Handles has to be perpendicular to the Sewing Lines.
Adjusting the Control Handles on the Interactive Curve Tool may cause problems both Grading and Drawing.
So I want to learn the same concept for “Spline - Fixed Tool” (Maybe with an extra 2 guide nodes.)
Can you give me an example for that?
Here is a part of a tutorial I’m busy writing based on the tutorial that I posted in the topic Super Easy Way to do the Armhole Curves:
BHC1 - In my example, I have used the Point – on Perpendicular tool and click on the shoulder tip point A2 and then on the neck side point A5 to create a point at 90° to the back shoulder line. The formula entered for the length is Line_A_A4_Across_Back/3. No other setting needs to be adjusted.
My reason for using this formula is that I would like an even curve stepping inwards a distance and downwards a distance, but since the distances involved won’t form a circle, but rather a portion of an ellipse, it is divided by 3 instead of by 2 which would happen if I was creating a portion of a circle.
If the curve handle should protrude into the fabric of the back bodice too much, I would divide the longest line by 3.5 or 4 (or more), instead of 3. This applies to all of the curve handles as they are easily adjustable, individually, to create the most pleasing curve.
BHC2 – Here, I’ve used the Point – On Line tool and the length formula CurrentLength/3. This is actually the same formula as in the previous tool and I could have use the formula Line_A2_BCH1 but I may wish to change the formula, so I’d rather keep the two formulas totally independent of each other.
BHC3 – Again, I’ve used the Point – On Line tool but the length formula CurrentLength/2 because this is more a portion of a circle than an ellipse.
BHC4 - I have used the Point – on Perpendicular tool and clicked on the armpit point A3 and then on the back seam side point A6_Side_Seam_Back to create a point at 90° to the back side seam line. The formula entered for the length is Line_A1_A3/1.5 because I would like a slightly deeper circle portion. Change the Rotation to 180° to place the point correctly.
Back Curve = Pick up the Spline – Fixed tool and click on points A2, BCH1, BCH2, A4_Across_Back (section 1), BCH3, BCH4, A3 (section 2). Hit Enter.
Question 1) I don’t understand why you did click A5 (the Neck Point) in the first place while using Point On Perpendicular Tool?
The line created is not perpendicular to the shoulder line (A2-A5) here.
???
Question 2) I don’t understand what does this formula mean?
Line_A_A4_Across_Back/3
Is that “Across Back measurement * 1/3?”
Question 3) You did not tell how you draw BCH1?
Question 4) What does this formula mean?
Line_A2_BHC1
Question 5) What does this formula mean?
CurrentLength/3
Yes it is… Line_A2_BCH1 is prependicluar to Line_A2_A5 or Line_A5_A2 whichever way the tool was drawn:
“Line_A_A4_Across_Back”… no. It’s the line length from point A to point A4_Across_Back.
“* 1/3”… yes. Sort of. The “/” (backslash) is the division symbol… so it means the length of Line_A_A4_Across_Back divided by 3. While equal in value, it’s semantically different. Plus you would probaby have to write it as:
Line_A_A4_Across_Back * (1 / 3)… but it just makes more sense to write it as Line_A_A4_Across_Back / 3.
BTW… I recomend to put spaces between values and operators - it’s easier to read. And personally I would eliminate some of the underscores so it reads:
Line_A_AcrossBack / 3
but that’s my preference.
Yes she did:
BHC1 - In my example, I have used the Point – on Perpendicular tool and click on the shoulder tip point A2 and then on the neck side point A5 to create a point at 90° to the back shoulder line. The formula entered for the length is Line_A_A4_Across_Back/3 .
The length of the line from point A2 to BHC1.
Let me break it down…
Line_ means the length of a line. A2 is the First point. “_” seperator - variable names can not have spaces in them. BHC1 is the second point.
If it had been AngleLine_A2_BHC1… then it would have been the angle of the line from A2 to BHC1.
CurrentLength is an Alias variable name. For example:
Length = 5.5 cm
When creating a “Mid” Point - On line on the Line_A2_A5 the tool just uses the current length of the line, which is the same as writing Line_A2_A5.
Length = 5.5 cm
“/2”… divide by 2. In other words the Midpoint tool divides a line in 2, and create a point.
Pick up the tool and do exactly what I say in the instructions. Then you will see why I give such detailed instructions.
It means the line between A and A4_Across_Back divided by 3
See question 1
It’s the line that you would’ve created in Question 1 if you’d followed the directions.
It is the distance between the 2 nodes selected if there’s a line between them, divided by 3.
Sorry, @Douglas , I didn’t see that you’d replied.
How did you create
Question 1) The node A?
Question2 ) The Node “A4_Across_Back
Aaaah… it’s the base point of the 1st draftblock. It’s created when you start a New pattern"
The basepoint name & dot of any block is always in Red.
Look at the properties of the tool… it will tell you. In this case it is the midpoint between A and A1.
Question 1) How did she find the node A2. The shoulder Point from the node A?
Question 2) I didnt’ understand the logic when I see the created curve line with Spline Fixed tool?
Because the line did not go through the points BCH1 BCH3 BCH4
???
I had assumed It followes the nodes you created?
You can not estimate how the curve line’s gonna be while creating the guide nodes?
Question 3) Is there a way to draw a curvy line which follows your guide nodes?
I only used measurements for the armhole area. The rest is only there to give an idea and the main idea was to teach others how to make curves, not how to draft a bodice. Often, when drafting, A2 is about 1cm from A in my picture.
No, the curve line doesn’t go through the control handle points, but it does go through the main points of the armhole.
You can read up a bit about it here: Curvature handles on spline points — Onshape
Here’s another one: Spline
and here’s one that you can move around to see what happens: Interpolating cubic B-spline
Yes, you’ll just have to create a whole lot more of them very close together.
I prefer my way. 
Question 2.2) I confused with the terms.
As far as I understand (From your previous answers) Fixed tools do not have Control Handles.
Rather than Interactive Tools have control handles? Like Curve - Interactive Spline - Interactive So you can adjust by dragging those control handles manually?
Maybe there are two terms on Spline Fixed Tool? A) Main Nodes B) Secondary Nodes (As you say Control Handle nodes) etc.
Question 3.2) Can you draw a example for this?
Because those are control points that control the bezier curve. The curve does not go through the comtrol points, but is cotrolled by them.
Yes… use the Spline - Interactive tool instead.
But then you have to deal with the control handles in a different manner to make it properly resize to different measurement files.
Does a curve created with
Question 1) Spline - Interactive Tool redrawn properly when Grading applied?
Question 2) Splne - Fixed Tool redrawn properly when Grading applied?
They both can resize. The control points are handled different. With Interactive curves the control points are within the curve / spline tool, where with the fixed curves the control points come from other tool points. By nature the fixed curve control points are porbably already adjusting to the tool’s formula, where with inter active cuvres you have to add formulas to the control pints to get smooth curves that resize properly. The topic has been discussed ad nauseam on the forums so I’m not going to rehash the topic.
You can try this topic…
Ok, I’m going to explain this once more. The only difference between the 2 splines is that the Spline - Interactive tool uses the formulas inside the Properties & doesn’t need the control handle points and the Spline - Fixed tool has points placed outside of the curve that are used when making a curve. Either way, the 2 tools use the same formulas to place the control handles at the same places to create a curve that is controlled and should maintain its shape over a number of sizes (when grading is applied).
The same formulas for the length and angle of the control handles are used in both tools, the interactive tool has the formulas internally and the fixed has the formulas externally.
If you choose to use the Interactive tool without the formulas (choosing to drag the control handles around until the curve “looks” good), there is nothing anchoring the control handles to the pattern, so they won’t resize and the curves will become distorted when grading.
Here, I have drawn an interactive curve over the fixed curve. The control handles are visible and the curve handles have been dragged over the control points previously created. This is a size 32:
This is a size 42:
Notice that the curve handles are now shorter than the control points and that the values in the formulas didn’t change.
An even better example on the bottom of the armhole curve. Size 32:
Size 42:
Now, instead of just dragging the control handles, I’ve used the control point formulas in the formula boxes. Size 32:
Size 42:
Notice that the curve remains true to the curve below it, that the curve handles remain on top of the control points and that the formulas remain the same but the values change between sizes.
This means that it is grading properly over a number of sizes and that you have 2 methods that achieve the same results and 1 that doesn’t. You are welcome to choose which method you would like to use and you may develop other theories on formulas to use - everyone does, I have myself which I have shared with everyone.
I think that this is most clear now.
Thank you very much for sharing your method as well. I appreciate your detailed answers.
Then I’ll add formulas to keep the curve while drawing in Spline - Interactive tool.
Another question for Spline Fixed Example
Question 1)
A3 : It looks like Underarm Armhole point. A6 : Side Seam Back??? Where is It? It is not shown in the images.
Question 2) What does Rotation do while drawing BCH4?
As mentioned before, this is only a partial pattern that I drafted to get the armhole for a different tutorial that I’m working on, but you can see exactly where all of the points are in this image. Please note that the side seams are usually a lot further away in a full pattern, than in this image.
A6 will normally be at the waist and the angle of the line will normally be established by the bust to waist reduction used in the darts of the pattern.
Normally you will only enter 180° in here to switch the point to the other side of the starting point, but mostly it will remain at 0°.
