Advanced methods and practise

From Valentina Project's Wiki
Jump to navigation Jump to search
This page contains changes which are not marked for translation.

Other languages:
English

Planning patternmaking with Valentina[edit | edit source]

The purpose of this section is not to learn patternmaking, but to help first users of Valentina to avoid beginners' mistakes.

When computerising patterns, the aim is to obtain correct and accurate results as well as a parametric behaviour.

It is important to keep in mind that the patternmaking method itself does not change when using Valentina instead of drawing with a pen, but it requires some planned steps.

For example, it is useless to draft a bodice block that would not be planned for evolving sizes and not adjusted for future transformations.


  • Prerequisites

It is highly recommended to computerize a pattern firstly drawn by hand (and graded if the aim is to obtain a multisize pattern), as well as making a measurements and variables independent table before starting, including every known result to obtain, such as the armhole and neckline lengths.

In this table, organise the variables : measurements, increments, preview calculations, and results to obtain ; this method avoids to have to change afterwards afterwards the categorisation.

A good method is also to list the points labels on the manual draft and to avoid to choose the default labels (A1, A2, ...) ; even if labels can be changed afterwards, the modification may be tedious since it implies to change each calculation where the label point has been used.


  • Lines of construction

As by hand, the vertical and horizontal lines of construction have to be drafted first. There is no particularity there, but do not forget to place the lines according to prerequisite variables.


  • Points of construction

This is a crucial step to obtain a transformable pattern.

The position of some points varies when simply changing the increments values in most patternmaking methods : bust, waist and hips calculations evolve by simply changing the ease values, the armhole height can be modified by modifying an increment value, ...

But the shaping of parametric curves may be a quite long-lasting operation, it is thus wise to plan the drawing such that when moving points, the curve moves also.

This is particularly true when drawing the neckline : when drafting the basic bodice block, you routinely put the 1/2 basic neckline width point, then you draw the neckline curve. The problem is when transforming the basic block, you have to increase the neckline most often, and the beginning of the neckline curve has to be moved along the shoulder line. At this step, if an additional point has not been placed to ancicipate the move of the neckline curve, this curve has to be drafted again.


Planning patternmaking neckline 1.PNG

Planning patternmaking neckline 2.PNG

Shaping curves[edit | edit source]

How to shape a parametric Bezier curve - Example of the neckline[edit | edit source]

This example explains how to shape a parametric Bezier curve. This is only one method amongst many others, but it has the advantage to be both (quite) simple and accurate for non experts in mathematical issues, and to anticipate the transformation of the basic blocks.

This method is based on cubic Bezier curves according to this pattern :


Bezier rec.png


It uses 4 points, A being the curve start point, D the curve end point, points B and C are used as control handles to shape the curve which passes through a point L4=R1. This point L4=R1 is the result of successive divisions by half of segments AB, BC, CD, then L2H, HR3, and at last L3R2.


Applying this method, it is possible to draft the front neckline as follows :


Advanced Methods Shaping Curves Neckline Front.PNG


The curve has to be shaped between points s2 and enc1, the aim is to define the location of points A6 and A17 which are control handles, and to obtain that this location allows a parametric behaviour of the curve.

First we know that the curve angle at point enc1 must be at 90 deg, so point A6 must be a perpendicular point to the front center line. At the beginning, the distance between enc1 and A6 is defined at random with an absolute value.

The angle curve at point s2 varies according to patternmaking methods, at the beginning the best is to define it at 270 deg. The distance between s2 and A17 is defined at random with an absolute value.

The midpoints A18, A19, ..., A25, are created.

It is now possible to adjust the location of points A6 and A17 to obtain the result you wish, by changing the distances enc1A6 and s2A17, and possibly the angle at point A17. This can be done for example if you know by which 3rd point the curve has to pass through, or you know the curve length, ...

Once the optimal result is obtained, it has to be translated in parametric terms, since the distances and angles used to place points A6 and A17 have been defined with absolute values.

The distances can be defined using a simple rule of 3 :

enc1A6=(s1s2)*Absolute_Value_enc1A6_Found_By_Adjusting_Curve/Absolute_Value_s1s2 ;

s2A17=(s1enc1)*Absolute_Value_s2A17_Found_By_Adjusting_Curve/Absolute_Value_s1enc1

The angle of the line s2A17 can be defined by reference to the angle of line s2d1 which is the shoulder line (since in certain patternmaking methods, the angle of the shoulder line varies from size to size).

Once the front neckline curve is drafted and adopts a parametric behaviour, do the same for the back neckline curve where enc2 and s4 are start and end points of the curve, and points A12 and A13 control handles points.

Just be careful about the direction of the curve at point s4 to obtain a smooth adjustement between the front and the back necklines. To do so, the angle of the line s4A12 has to be defined at (180-Angle_Line_s2A17).


Advanced Methods Shaping Curves Neckline Back 1.PNG


When the basic pattern is afterwards transformed, it is very simple to adjust if necessary the neckline curves by just changing the location of the points A6, A17, A12 and A13.

Conditional calculations[edit | edit source]

Basic syntax[edit | edit source]

It is possible to create conditional calculations using C++ style syntax for 'if then else' operator, that is to say ?:

Basically, in patterndrafting, we will most often use this operator to specify to Valentina to apply one value or another when some parameters vary.

Using this specification is nevertheless quite different from simply using the measurements table, since the chosen increment or preview calculation do not necessarily vary according to the general standard of the pattern, but according for example to the difference between the waist and the bust circumferences, which may imply to change the waist darts quantity and/or size.

In this example, A 'Dart_Size' increment is created, specifying that if the difference between the waist and bust circumferences is greater than 15, the dart size will be equal to 1.75, and 1.5 in the other case.

It can be written as follows :

(@TP-@TTf)>15?1,75:1,5

That is to say IF Bust_Circumf - Waist_Circumf is greater than 15, THEN IF TRUE (operator ?) Dart_Size = 1.75, ELSE IF FALSE (operator :) Dart_Size = 1.5

When uploading a new measurements table, Valentina will automatically apply the conditional value according to the waist and bust circumferences.

In the present example, Valentina applies a 1.75 cm value, since the bust and waist circumferences are each 83 and 64 cms, and the difference is 17 cms.


Conditional calculations 1.PNG


Conditional calculations 2.PNG


Evolving conditions[edit | edit source]

It is as well possible to write an evolving conditional expression, by groups of sizes for example.

On the following screenshot, you can see that the shape of the front armhole curve, evolves according to the position of point A19, itself evolving according to the bust circumference called @TP measurement :

@TP<100?1:(@TP<110?1,25:1,35)

It is thus indicated to Valentina that position of point A19 from point A18, is meant to be 1,00 cm when the bust circumference is less than 100 cms ; 1.25 cms when the bust circumference is less than 110 cms ; and 1.35 cms when the bust circumference is equal or greater than 110 cms.


Conditional calculations 3.PNG

Darts[edit | edit source]

Editing in Inkskape[edit | edit source]

Valentina does not provide grading tools nor multisize editing tools for the moment.

You can netherveless edit a graded pattern using free opensource Inskcape software.


Inkscape is a vectorial images software, allowing perfect manipulation of Valentina patterns to create graded versions of patterns, following these steps :


  • Create a folder aimed to contain temporary files to achieve gradation.


  • Open Inkscape and create a template file saved in the created folder.

In preferences properties, define the page size as A1 or another appropriate size.

Create a first layer for the graded patter, then one layer per size to import.

Keep this file blank.


  • To grade a pattern, open the template file and save it as the final file containing the graded pattern.


  • In Valentina, export the pattern in each size as a .svg file, skipping the layout stage.

Do not keep margin seams, and keep labels and the grainline only in one size.


  • In Inskape, import in each layer the corresponding .svg file.


  • In each layer,

→ select the imported image and first set the contour and color parameters (different in each layer) ;

→ the imported image being considered as a single object in Inkscape, cannot be processed as a whole for further gradation, so degroup it, and group again each piece of the pattern ;

→ select all pieces and duplicate, then transfer them to the layer created for the final pattern ;

→ once all pieces in each size have been transfered, open the final layer ;

→ activate the magnetism tool, including magnetism on paths and handles ;

→ anchor each similar piece of pattern to the same point ;

→ place the final pattern on the page ;

→ print the file directly if the printer allows it, or export before printing in a A4 multipages editor (not provided by Inkscape).