Summary

This is an exercise in creating a 2D YinYang in OpenSCAD. The objective is to provide an example of the steps taken and tools used in OpenSCAD to create a simple 2D model.

The programming is broken into more modules than required in order to make the individual steps and concepts more understandable. This should not be taken as a "best practice" approach to OpenSCAD programming.

How I Designed This

OpenSCAD

            <div><p>Created using OpenSCAD version 2017.01.20 with the Customizer enabled.</p></div>

Program

Pseudocode

            <div><p>Step 1 - Create predefined variables.  These variables can be changed if the user is using Thingiverse Customizer or the OpenSCAD Customizer plug-in.<br>Step 2 - Create calculated variables.<br>Step 3 - Draw half of the large circle.<br>Step 4 - Cut out the medium circle portion of the large half circle.<br>Step 5 - Add a medium half circle to the modified large half circle.<br>Step 6 - Add a small circle below the modified large half circle.<br>Step 7 - Cut out a small half circle from the modified large half circle.<br>This is the Black portion of the YinYang.<br>Step 8 - Rotate and raise a copy of the shape created in Step 7.<br>This it the White portion of the YinYang.</p><ul><li>border()<br>Create border.  The diameter of the border is the diameter of the large circle plus two times the border thickness.</li><li><p>main()<br>Start execution of the program, call the border() module if required and assign colors to the two portions of the YinYang.</p></li><li>In Step 8 the 2D object is built on a different XY plane to avoid display flickering that can occur due to overlapping 2D shapes.</li></ul></div>                <p class="detail-title"><strong>User Definable Variables</strong></p>            <div><ul><li><p>borderT<br>Border thickness in mm.  Can be .25 to 1.</p></li><li><p>borderF<br>Border On/Off flag.  True of False.</p></li><li>largeCircleD<br>Diameter of the large circle in the YinYang.  This is used to calculate all other dimensions.</li></ul></div>                <p class="detail-title"><strong>Predefined Modules</strong></p>            <div><ul><li><p>circle()<br>Create a 2D circle.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle</a></p></li><li><p>color()<br>Assign a display color to the object.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#color">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#color</a></p></li><li><p>difference()<br>"Subtract" all subsequent shapes from the first listed.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/CSG_Modelling#difference">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/CSG_Modelling#difference</a></p></li><li><p>if()<br>Execute code based on a test.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Conditional_and_Iterator_Functions#If_Statement">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Conditional_and_Iterator_Functions#If_Statement</a></p></li><li><p>square()<br>Create a 2D square or rectangle.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#square">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#square</a></p></li><li><p>rotate()<br>Rotate the object on the X, Y and Z axis.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#rotate">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#rotate</a></p></li><li>translate()<br>Move the object on the X, Y and Z axis.<br><a rel="nofollow" href="https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#translate">https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#translate</a></li></ul></div>                <p class="detail-title"><strong>Programmer Defined Modules (See Pseudocode for descriptions)</strong></p>            <div><ul><li>border()</li><li>main()</li><li>step1() - step8()</li></ul></div>                <p class="detail-title"><strong>Programming Concepts</strong></p>            <div><ul><li>Customizer markup.</li><li>Parametric code.</li><li>Programmer defined modules.</li><li>if() with a boolean variable.</li></ul></div>

YinYang 2D Model - Parametric