Using Curve Tool to draw complex arrows, an apple and DNA
July 27th, 2006
Curve Tool is also useful for drawing more complex objects. Here we describe how to draw complex arrow, objects like an apple and DNA segment that could be used to create the impression of twisted DNA. Refer to Essential Drawing Tools I, Setting up Your Personal Workspace and Using Curve Tool previous articles for more information on basics drawing strategies in PowerPoint.
Drawing curved arrows. In addition to drawing line with three editing points, one can create the same final object using two editing points and a Bezier method. These editing points have properties that could be accessed in Edit Points dialog box as described in Fig 38a in preceding article. The procedure is illustrated in Fig. 40 below. First, draw the straight arrow using Arrow Tool, highlight the arrow, click the right mouse button and select Edit Points from the menu in dialog box. Next point the pointer to the upper anchor point, click the right mouse button and select Smooth Point from the menu. An additional rectangle (open) with a straight line originating from the selected point will appear below the mouse pointer. This is the Bezier Tool. Drag the Bezier handle (open rectangle) toward the right and see the appearing bend in the line. The same could be performed with the lower anchor point to achieve symmetrical effect. Note that the bent could be controlled by the position of the Bezier handle.
Figure 40. Drawing steps leading to curved arrow using Bezier Tool. Note that the shown arrow has only two editing points: beginning and the end.
More complex arrow could be transformed using the same Bezier Tool. In the Fig. 41 on top an arrow was drawn using 4 anchor points. The same effect could be achieved using just two anchor points in a straight arrow and Bezier Tool to induce the curvature.
Hint: When drawing more complex objects it is very useful to have Grid and Guides on the screen. These do not print and neither show in on screen presentation. They are only on your screen computer to aid in drawing objects and help maintain symmetrical proportions, horizontal and vertical positioning. To activate Grid and Guides select View pull down menu and click Grid and Guides. In the subsequent menu click Display grid on screen (this dialog box is shown in Fig. 7 from Drawing pentagon, hexagon and other cyclic structures).
Figure 41. Drawing steps leading to a complex arrow.
Drawing an apple using Curve and Bezier Tools. Having gained some PowerPoint drawing experience, we can make more complex object such an apple. We begin with the four anchor points containing symmetrical oval, drawn using Curve Tool. Use the grid to maintain proportions. The shape closes automatically when the fifth (double) click is made directly over the first anchor point. The step-by-step procedure to draw an apple is shown in Fig. 42. To induce top and bottom cleavage, introduce two additional anchor points. At the step 4 copy the finished apple shape and overlap it with the original. The bottom object will have changed color and serve as a template to maintain the shape during further manipulations. To make the bite site we add a single additional anchor point on the left. However, in contrast to selecting Smooth Point from the menu Edit Points as we did before, we select Corner Point to produce sharp turn at the upper and lower side of the prospective bite (Fig. 42). Any imperfections at the original bottom left anchor point could be smoothened using Straight Point Tool.
Figure 42. Drawing steps leading to an apple.
Drawing DNA. The basic strategy in drawing DNA molecule is somewhat different from previous objects only because this complex molecule consists of many small basic shapes. The most important building block for DNA is an 8-anchor point shape illustrated in Fig. 43.
Hint: When drawing objects that later may be part of more complex structures it is very useful to draw them well magnified using the full space of the slide. In the full scale it is much easier to take advantage of the grid and work out small glitches of the drawing. After they are finished you may downsize them without changing proportions using Format>AutoShape> dialog box and Size tab with selected Lock aspect ratio.
Figure 43. Drawing steps leading to DNA.
Drawing the initial building block for DNA construction may require some tweaking before short DNA molecule is assembled. Additional small cylinders that are necessary for the final DNA molecule are easier to build from common rectangles. To preserve the proper DNA turning direction it is important to work with Bring to front and Bring to back buttons at each of the DNA turns. Useful hint: try to envision that DNA, when looked at from left to right, is turning toward you. Then place each basic block either in front or in the back, relative to each other, accordingly.