By popular demand, we have implemented a very intuitive system of managing fixed bond angles and lengths when drawing structures in ChemDoodle v1.4.0. Previously, angles and lengths were fixed by default and you could break from both restraints by holding the shift key. This system was not completely manageable as there were no default settings for controlling fixed angles or lengths. We have competely changed the drawing system to provide easy management of these restraints and even provided an extra snap-to-grid feature for even further control. The following image shows the effects of fixing angles and lengths.

UPDATE: ChemDoodle v1.4.0 was released on 12/19/08.

To begin, there are now two options in the Preferences dialog under the General tab for setting the default restraints on angles and lengths as shown in the image below (Also notice the new snap-to-grid options). You may individually restrain either angles, lengths or both.

Placing bonds when drawing molecules is now more controllable as they will follow certain rules based on which restraints you have enabled. To make things even more manageable, the shift and alt keys will toggle fixed lengths and fixed angles respectively. These keys modify your settings in XOR fashion. A break down of the combinations for fixed lengths is shown in the following table.

Is the fixed bond length setting selected? Is the shift key being held? Are bond lengths fixed?
yes yes no
yes no yes
no yes yes
no no no

This entire system may seem overly complicated, but once you try it out, I guarantee it is intuitive and very powerful. These settings will take effect when adding new bonds or when moving a atom in a bond that has nothing connected to it on at least one side. Also, don’t forget the blue optimize zone circle that will choose the optimal position for a new bond when you move your mouse pointer inside of it.

Lastly, let me just describe the new “snap-to-grid” feature. In the same section of the Preferences dialog (see the above image), there is another new option for managing the grid. You may have gestures snap to a 5 pixel grid, a 10 pixel grid, or no grid by default. This new grid option will help you to place items and align them with ease. Also note that there are new object alignment and distribution functions that have been added to ChemDoodle v1.4.0 to help in all aspects of producing quality figures.

ChemDoodle v1.4.0 will contain new features for managing how structures are drawn. Using these features, you may more efficiently draw structures and more quickly finish your figures. It is a goal of ours to create a chemical drawing tool that is intuitive and adapts to the user’s drawing preferences. We believe this feature is a great way of providing that versatility. Expect to see ChemDoodle v1.4.0 released in late November.