Help creating Celtic knots in Designer 2

[CJRM]

My searching skills failed to turn anything up, so I'm asking for help from the Forum brains trust.

I'm working on a project that involves recreating some Celtic knot work. The first attachment shows a guide I'm using to create a part of the knot. The finished end on the left is the look I'm going for.

I could draw it all in pieces, but I was playing with the v2 features to see if I could shortcut things. My hope was to use Shape Builder to stitch together the knot sections after drawing the overlapping paths of the knot in some way.

I drew a section of knot work as one long thin line (see the second attachment), fattened the line, and then used Expand Stroke to create a wide 'path' from that. Unfortunately, where the line crosses itself, Expand Stroke just merges everything into the same shape. Instead of one path crossing over or under another I now have 'road intersections' were the crossing paths are merged, as per my third attachment.

I tried to use the Contour tool, but it causes the same issue. Where the line crosses itself the offset does not preserve the overlap. See the fourth attachment which shows the result of using the Contour tool twice, once inward and once outward. The original line runs through the middle.

I could break the original thin line apart and use Expand Stroke or the Contour tool on each separate piece, but the pieces won't connect properly and I'll probably spend more time fixing things up than I would just drawing each piece of the knot the hard way.

Any thoughts?

[v_kyr]

2 hours ago, CJRM said:

My searching skills failed to turn anything up, so I'm asking for help from the Forum brains trust.

Search this way ...

• celtic knots site:forum.affinity.serif.com

[lepr]

4 hours ago, CJRM said:

I could break the original thin line apart and use Expand Stroke or the Contour tool on each separate piece, but the pieces won't connect properly and I'll probably spend more time fixing things up than I would just drawing each piece of the knot the hard way.

Any thoughts?

Shape Builder Tool will clean up quickly, as in attached video.

 

 

[CJRM]

Thank you! That showed me what I was overlooking. The step I was missing was breaking apart the line before performing Expand Stroke. My bad.

[firstdefence]

I think that not only could you create a celtic knot layout document you could Asset the various curve shapes so that making a celtic knot becomes a process of dragging assets onto the celtic knot layout with snapping to grid set as an aid to alignment.

[CJRM]

Indeed. And that seems to work!

[CJRM]

Thanks for the advice. Particularly @lepr. Still working on the more advanced pieces, but I have what I need to make it all work now.

[Hangman]

Hi @CJRM,

This may or may not be of interest... It was something I played around with just after the Shape Builder tool was added to version 2 and shows how the tool is perfect for creating this kind of artwork, though it does use a bit of a technical approach...

Step 1

• Create a new 100 mm x 100 mm, 300 dpi document
• Add horizontal, vertical and 30° guides centred of the canvas
• Create three circles with a diameter of 20 mm and a 10pt centred stroke
• Distribute the circles horizontally at their stroke centres
• Group the three circles

Step 2

• Duplicate the group of three circles and further duplicate the circle on the right to create a fourth circle
• Transform the X, Y coordinates of the fourth circle mathematically along a 60° path to ensure accurate positioning

Radius R = 10 mm
Angle θ = 60°

X Transform
X = R x cos(θ)
X = 10 x cos(60)
X = 5 mm

Y Transform
Y = R x sin(θ)
Y = 10 x sin(60)
Y = -8.660254 mm

 

Step 3

• Select the circles from Step 1 and convert to curve’s
• Cut curve’s along their common horizontal centres and delete alternate sides

Step 4

• Join the remaining curve’s to create a single curve

Step 5

• Create a circle to indicate the outer edge of the graphic and to act as a positioning guide for the curves. As the Chord length (C) and the Angle (β) are known, the radius of the circle required can be calculated using some basic trigonometry

Chord length C = 60 mm
Angle β = 30°
Height H = 1/2C x tan(β)

H = 30 x tan(30)
H = 30 x 0.57735
H = 17.320508 mm

The radius of the required circle will be the hypotenuse of the right angled triangle…

Height H = 17.320508 mm
Base 1/2C = 30 mm

Hypotenuse R = √(Height² + Base²)
R = √(17.320508² + 30²)
R = √(300 + 900)
R = √(1,200)
R = 34.641016 mm

 

 

Step 6

• Select the curve and rotate it 240°

Step 7

• Move the curve along a 30° path by distance H until the ends of the Chord touch the circular guide created in Step 5 at the 90° and 120° points by transforming the X and Y values as follows:

X = 1/2C / 2 = -15 mm
Y = H / 2 = -8.660254 mm

Step 8

• With the curve selected set its transform origin to the centre of the canvas
• Duplicate the curve and rotate it by 60°
• Step and repeat to create a total of six curves

 

Step 9

• Select the group of four circles created in Step 2 and convert to curves
• Cut the three horizontally aligned curves along their common horizontal centres and delete alternate sides

Step 10

• Join the three curve’s to create a single curve
• Cut the fourth offset curve at its 120° and 300° points and delete the right side

Step 11

• Rotate the grouped curve's 60°
   

Step 12

• Transform the X, Y values of the rotated curve's

X = 1/2C / 3 = -5 mm
Y = H / 6 = -2.8867513 mm

Step 13

• Select the grouped curve's and set their transform origin to the centre of the canvas
• Duplicate the curve's and rotate by 60°
• Step and repeat to create a total of six grouped curve's

Step 14

• The combined curve's rotated and positioned
• Realising the points at which the curve's overlap and intersect are not correct change the stroke width for all curve's to 8.75pt

 

Step 15

• Select all curve's and Expand their Strokes
• The curve's can’t be joined where they meet because doing so prevents the Shape Builder tool from merging the curve's correctly
• Go to town with the Shape Builder tool merging the curve's so they over and underlap appropriately

Step 16

• Create additional circular guides to mark the points where the Red, Yellow and Blue curve's join
• Select the node at each joining point and move it until it snaps to the circular guides

Step 17

• Add a stroke to the curve's and remove their fill

 

Conclusion

• The key takeaway for me was that precision is key when doing something like this, the Shape Builder tool works flawlessly when everything is positioned perfectly.

 

[CJRM]

@Hangman it says it can't show me whatever you included because I "do not have permission to see it." Strange.

[Hangman]

8 hours ago, CJRM said:

 it says it can't show me whatever you included because I "do not have permission to see it." Strange.

Not sure what is going on there, it looks like there's some sort of glitch... I've updated the previous post so you can see the approach I took to creating the Celtic Knot using the Shape Builder tool, it's a bit technical but it worked really well...

[Oufti]

14 hours ago, CJRM said:

it says it can't show me whatever you included because I "do not have permission to see it."

Refreshing the page solved it for me. 

[CJRM]

@Hangman That's an extremely clear explanation. Nicely done! And I have to highlight your comment about "when everything is positioned perfectly" as I learned that the hard way on this work. Small deviations in positioning points on a curve would cause unexpected problems. Your approach using exact math may look harder at first, but it will save a lot of time in the long run.

[Hangman]

Hi @CJRM,

Exactly, when I attempted to create the Celtic Knot originally without that level of precision I ended up with loads of tiny shapes when using the Shape Builder tool because the lines weren't overlapping in exactly the right place and subsequently things looked messy in the final version which was the main reason for adopting a more mathematical approach which worked out perfectly when applying the shape Builder tool.

It probably looks way more complex than it is but it's really only some quite basic maths used for positioning the various elements.

You'll have to upload some of your finished designs, it would be great to see what you produce...