SecuriDesign Pattern Generator
Envelopes tab of the SecuriDesign Pattern dialog controls how the envelope curves are treated. An envelope curve is one of two curves that were selected before running Pattern Generator and which define how the pattern is built.
The Envelopes tab contains two identical sections for the two control curves used to build a pattern. The first envelope is outlined with blue in the preview window, the second is drawn in red; and each section of the dialog is keyed with the same color.
Each envelope settings section contains the following options:
Closed Path Origin
The beginning of a curve is assumed to be at the first curve node. If
this is obvious for open curves like lines, it could be hard to determine
the beginning of a circle. Also, when a closed curve is rotated, its
starting point moves as well making the two envelopes to start at
different places. This would result in distorted pattern:
The small colored dots on each envelope curve mark the curve beginning. You can see that the second (red) envelope was rotated clockwise by about 30°.
To align the two curves and straighten the pattern, you can offset the beginning of either envelope to bring them to the same geometrical point. The Closed Path Origin serves this purpose. Its value is measured in tenths of percent (0.1%), thus a value of 500 equals to 50% of curve length. In the above example, the offset of 30 degrees corresponds to about 8.3% of the total curve length (30°/360°), then entering "-83" in the Closed Path Origin field for the second envelope should bring the beginning of the curve inline with the first envelope.
The direction of a curve is determined by the way it was created. If
the preview shows the pattern messed up like in the following
illustration, this means that the two envelope curves follow opposite
directions. Reverse the direction of either envelope to straighten the
You can see that the first (blue) envelope starts at the right side while the second one starts at the left side according to the markers.
After you reverse the direction of the first envelope, you get an
Uniform Distribution and Use The Following Settings
When the pattern is created, each envelope curve is sampled uniformly along its whole length. This is the default behavior of Pattern Generator. However you can add irregularities to the pattern by choosing Use The Following Settings option. In this case, use the controls below the option button to specify the way the irregularity is formed.
The same pattern but "Sin" function with frequency = 3 used
for the first envelope:
Here is another example how irregular pattern can change the look of a
security design. The same pattern design shown in the very first dialog
screenshot on this page but this time with non-uniform pattern
Function, Frequency, Amplitude, and Phase
These settings specify how the irregular patterns are created. The Function list shows a function to use to modulate the distribution of a pattern.
The second list to the right of the function list allows to choose which function component to use. Every function in SecuriDesign actually contains two function component definitions - X and Y. This list allows to choose the function component to use. See Function Editor for more information on creating and using functions.
Frequency specifies how many "peaks" of distortion to be created.
Amplitude determines the amount of irregularity to add to the pattern. 0 means no disturbance while 100 denotes a very strong distortion.
Phase Offset specifies the position of the disturbance peaks. For example:
Phase Offset = 0%:
Phase Offset = 50%
Use Source Function
This option is only available for envelopes created with Contour Generator which stores special information along with the contour curves that allows to recreate the contours each time a pattern is created to produce better mathematical fit for the patterns within the envelopes.
Let's illustrate this on the following example. Let's take a base curve like this and build two parallel curves using Contour Generator:
When a pattern is created, uniformly distributed sample points are placed at equal distances on both envelope curves and the resulting pattern follows the direction of lines connecting corresponding sampling points. The following pictures illustrate the pattern built using the two generated envelopes as if they were hand-drawn in CorelDRAW (without using the special information stored with the curves by the Contour Generator):
However if the sampling points are placed on the base (control) curve first and then reflected to the envelopes using the same methods that were used when creating the contour curves, the resulting distribution of sampling points along the envelope curves will be non-uniform but the pattern generated now has the expected effect:
Click the button to swap properties of the envelope curves. The first (blue in the preview window) envelope becomes the second one (red) and vice versa.
Copyright © 2002 by Alex Vakulenko. All rights reserved.