Node Editing: The Basics

I am sure you know that you can easily draw lines, curves, ellipses, circles, squares, rectangles, stars, polygons and more with CorelDRAW®, but what about other shapes? What if, for example, you wanted to draw a heart? How would you go about doing so? CorelDRAW doesn’t provide a “heart-shape” drawing tool. The only option is to roll up your sleeves and do some node editing.

Nodes are the foundation of any drawing program. Every line, even a simple straight line or curve, contains nodes. Figure 1 shows a diagonal line with a node at each end.

Figure 1 A straight line with a node at each end

Shapes drawn with the Rectangle, Ellipse, Polygon, Spiral and Grid tools contain nodes, too. These nodes, though, behave a little differently than nodes in curves. To create various shapes by editing nodes you really need to start with a curve. Fortunately, you can create a curve from any object you create with the various shape tools. The exceptions would be a spiral (which is already a curve) and a grid (which can’t be converted to anything else).

Between the nodes are what is known as segments. Segments can be either lines (straight segments) or curves (curved segments). Each type can be converted into the other type if need be.

There are several different types of nodes and the type of node determines how the associated segments will be shaped and how they will react as you push and pull at the control handles. The control handles are similar to nodes and they are stationed at the end of control lines that are drawn through each node. Normally you won’t see the control lines or the control handles; they only become visible when you click on a line, or shape, or select a node with the Shape tool.

This isn’t true in all cases, though. For example, if you draw a straight line with the Freehand tool as I did to create figure 1, and select one of the nodes with the Shape tool you won’t see any control line or control handles.

On the other hand, if you draw a curved line with the Freehand tool (or convert the line to a curve) and then click one end of that line with the Freehand tool, you’ll see the control line and the control handles (see figure 2).


Figure 2 A curved line with the control line and control handles visible

Note that the control lines are one-sided at the ends of the curve (with only one control handle) and that the node in the middle of the line has a two-sided control line with control handles at each end.

Clicking and dragging a node with the Shape tool will change the position of the node as well as changing the shape of the curve. Clicking and dragging a control handle will change the shape of the curve without moving the associated node.

If you haven’t already, fire up CorelDRAW and draw a curve with the Freehand tool. After drawing the curve, select the Shape tool and play around with the nodes. Move the nodes around and then try dragging the control handles. You can move the control handles inwards and outwards from the node they’re connected to as well as moving them around the node. Moving a control handle inward as you move it around will decrease the curved-ness of the curve while moving it outwards will accentuate the curve.

Note that you can move a selected node using the Arrow keys. You can’t move a control handle in this manner, though.

Different Types of Nodes
Earlier, I mentioned that there are different types of nodes. These are Cusp, Smooth and Symmetrical.

A symmetrical node has control handles that move in unison. The control lines on each side of a symmetrical node are always the same length. As you move one control handle toward the node, the other handle will move inward as well. This is equally true if you move one of the control handles away from the node. If you move one control handle of a symmetrical node upward, the other handle will move downward and vice-versa.

All of the above causes the curve that runs through a symmetrical node to be, well… symmetrical. That is, the curve will be similar on both sides of the node (see figure 3).

Figure 3 A curved line with a symmetrical node

A smooth node also has a straight control line that runs through it. This control line also has two control handles. However, unlike the symmetrical node, the sides of the control line can be of different lengths. Consequently, the curve, while smooth, will not necessarily be symmetrical (see figure 4).

Figure 4 A curved line with a smooth node

Cusp nodes are quite interesting. Not only can the control lines be of different lengths, the control handles at each end can move in different directions totally independent from each other. This allows the curve to bend sharply at a cusp node (see figure 5).



Figure 5 A curved line with a cusp node

The cusp node is just the thing we need to create a heart shape from a curve.

Drawing the Heart Shape
To get started with drawing your heart, open a new file in CorelDRAW and, using the Ellipse tool draw a vertical ellipse (see figure 6).


Figure 6 – Start with a vertical ellipse

Choose Arrange, Convert to Curves (CTRL + Q). Optionally, click the Convert to Curves icon on the Property Bar.

Doing so will convert the ellipse into a curve and enable you to select and edit the nodes.

Select the Shape tool, then click and drag a rectangle that encompasses the nodes at the top and bottom of the ellipse.

Press the Down Arrow key ten times. You’ll notice that the two nodes move downward. You’ll also notice that this changes the shape of your ellipse; in fact, it may start to resemble a shield.

Click and drag a rectangle around the leftmost node. Press the Left Arrow key six times.

Click and drag a rectangle around the rightmost node. Press the Right Arrow key six times.

You should start to see the beginnings of a heart shape (see figure 7).



Figure 7 Starting to take shape

Right-click the topmost node and choose Cusp from the Property Bar.

Press the Down Arrow key six times.

Click and drag the right control node straight up so that the curve on the right of your shape rounds upward to form the top right curve of the heart. Do the same with the left and you should have something that resembles figure 8.

Figure 8 Almost there

Note how changing the node to a cusp enables you to have that sharp point where the top halves of the heart meet.

Right-click the bottom node and choose Cusp from the menu.

Click and drag the right control handle up toward the control handle of the rightmost node.

Do the same with the left control handle, dragging it toward the control handle of the left node.

You should end up with a (nearly) perfect heart shape (see figure 9).

Figure 9 Final node editing

In figure 10, you can see my final shape. I moved the left and right nodes outward a little more and filled the shape with red.


Figure 10 Final heart shape created by node editing an ellipse

There’s a lot more you can do by editing nodes. I encourage you to play around and see what you can come up with.

Using Powerclips

We all know that Corel DRAW is great for illustration and for drawing shapes. Wouldn't it be great if we could use those shapes in combination with bitmaps, say photographs for example, to create some interesting and original artwork. It might be nice to be able to place a photograph inside a shape so we could use that in a newsletter, brochure or poster. "Masking" off the bitmap with a shape (and the shape can be pretty much anything you can create in Corel DRAW, including text) would be pretty fancy and you might expect it to be difficult to do. You may be surprised to find, then, how easy it is to accomplish in Corel DRAW. Embedding shapes or other objects, such as bitmaps, within other shapes or objects is called PowerClipping in Corel DRAW and it's fairly easy to do. Once you've added a PowerClip to another shape or image, you can manipulate the entire object as though it was just another simple shape. You can rotate and resize the object, for example, and you can even modify the embedded object. This article will show you how this can be accomplished with relative ease.

Getting Started
The first thing you'll want to do is open a new graphic in Corel DRAW. You can do this, after running Corel DRAW, by choosing File, New. Doing so will leave you with a clean slate in which to create your PowerClipped image.

Importing a Photograph
With the new file ready to go, it's time to add a bitmap image. You can choose one of your own photographs that you've created with a digital camera or scanned into your computer from a print, or you can search the Web for a photograph to use. If you use something from the Web and you'll be using it for more than simply this exercise, be sure to obtain any rights you may need to use that material.

You can add the bitmap image to the newly opened graphic by choosing File, Import. Doing so will open the Import dialog box (see figure 1).

After you have selected the image you want to import, the cursor will change and you can then click and drag the cursor to define where the imported image should be placed. Don't worry about getting it perfect because you can easily move and resize the imported image afterward.

Once you've defined where your bitmap image should go, release the mouse button and your image will appear. I'm using a photograph of an old corvette that I took a couple of summers ago while on vacation (see figure 3).


Adding Text
I'm going to place the image inside some text to create an image that might be used to advertise a classic car show. You may think that placing the photograph inside some text would be more difficult than placing it inside a simple shape. The truth is, though, it involves the same process and it's extremely easy to do.

With the imported photo added to the graphic, you can now add some text. This text will be used as the "container" for the photograph. To add the text, select the Text Tool, and click somewhere away from the imported photograph. I'm going to type the word "CARS" (see figure 4).



Lining Things Up
At this point it's time to line up the imported photograph and the newly entered text. To do so, simply choose the Pick Tool and move the text until it covers the imported photograph. You may need to resize the photograph and/or the text. You can do so using the Pick Tool. To do so, select the Pick Tool and click the object you want to edit and then click and drag one of the eight handles (the four corners and four midpoints). The goal here is to get the text to mostly cover the imported photograph (see figure 5).



Adding the PowerClip
With the text placed properly over the imported photograph, select the photograph using the Pick Tool. With the photograph selected, choose Effects, PowerClip, Place Inside Container. You'll see a large black arrow icon. Use the large arrow to click on the text (see figure 6).



Clicking on the text will turn it into a container that will contain the imported photograph (see figure 7).




Adding an Outline
With the imported photograph inserted in the text container, it's time to get a little fancy and finish up the poster artwork.

Right click one of the colors from the Color Picker to set the outline color. I'll use black for the example. With a color set, double-click the small pen icon in the lower right corner of the window. Doing so will bring up the Outline Pen dialog box (see figure 8).



Set the Character Spacing
To get even fancier, choose Text, Format Text and set the Character Spacing to a negative value. In my example I've set the spacing to -15.0% (see figure 9).



You can play with the value to see what works best for your choice of text and the imported photograph. The goal here is to scrunch the letters together to help the photograph show through in such a manner as to be recognizable (see figure 10).


Finishing Up
To finish up the poster, I added a blue rectangular background by drawing the shape using the Rectangle Tool. I then moved the rectangle to the back by choosing Arrange, Order, To Back. A final touch was the addition of the word "Classic" in a bold handwriting font. You can see the final image I created in figure 11.


There's more you can do, including editing the contents (the imported photograph) in place, and even manipulating the container and the contents using the Pick Tool… but I'll leave some of that for a future column. In the meantime, play around with this idea. It can be used to create original artwork for everything from greeting cards and invitations to posters, brochures and signs, as well as logos for Web sites. As an alternative to using an imported photograph and text, you can try using grouped shapes. Allow your imagination to guide you towards some really cool artwork.

How to draw mechanical threads

When it comes to drawing realistic-looking threads for either illustration or engineering drawings, many users often puzzle of just how to tackle the shape and shading aspects. Here's one basic technique you can try on your own using the tools available in CorelDRAW 11 to create machine-bolt style threads around a cylindrical object.

1. For the thread spiral, you'll be welding three basic objects together (two triangles and a rectangle). Draw a square by click-dragging with the Rectangle Tool (F6) while holding the Ctrl key to constrain its shape. Immediately convert the object to curves by choosing Arrange, Convert to Curves (Ctrl+Q).

2. Choose the Pick Tool (Spacebar) and double-click any of the four corner nodes in the shape. This will turn the square into a triangle to represent one end of the thread shape. This triangle will represent one end of the spiral thread.

3. Using the Rectangle Tool again create a rectangle to represent the middle of the thread. Make its thickness roughly two thirds that of your triangle (or scale it later to suit). Using the Pick Tool, position your triangle at one end. Rotate the triangle to point away from the rectangle center with the triangle's longest side touching the end of the rectangle.


4.Next, create a copy of the triangle for the other end of the rectangle. For a quick copy, use the Pick Tool and drag while clicking the right mouse button. Position the new copy at the other end of the rectangle. With the copy still selected, use the Property Bar Mirror buttons to flip the orientation of the triangle to point away from the rectangle center. With the objects exactly positioned, select all three at once and click the Quick Weld button in the Property Bar. This will cause all shapes to be combined into a single closed object (shown next).




5. To angle your new thread object, you'll need to use a Skew transformation. To do this quickly using the Pick Tool, click to display the rotation/skew handles and hold Ctrl while dragging a skew handle to constrain movement to 15-degree increments. Release the mouse button once the object has been skewed 15 degrees.


6. Create a new rectangle object to represent the screw cylinder to occupy the space between the two triangle ends of the thread. You'll need to layer it in back of the thread spiral by pressing Shift+PageDown. Then, make copies to create additional thread spirals by holding Ctrl as you drag while clicking the right mouse button. Then, use the Repeat command (Ctrl+R) for as many threads as you need. This will create the basic thread arrangement (as shown next).




7.Once your thread arrangement is complete, add color and shading to simulate depth and remove any applied outline colors. Using the Interactive Fill Tool (G) to create custom linear fountain fills. The next illustration shows a simple linear fountain fill using Green-White-Green applied to the cylinder object, and a similar color scheme applied to the threads. The cylinder's white highlight is offset slightly to simulate lighting direction. You will need to set the angle of the linear fountain fill applied to the threads to match the angle of created between the endpoints of the thread spiral.




8.By varying the cylinder size or the size, angle and/or frequency of the threads, you can quickly create any number of variations. Typical metallic color schemes can also be used to simulate different materials for your thread. Metals such as gold, copper, or steel can be characterized using the contrasting color values applied to their highlight and shadow colors. For gold, set the highlight color to 20 % yellow and the shadow color to 20 % magenta+20 % black+100 % yellow. For copper, set the highlight color to 5 % cyan+20 % magenta+20 percent yellow and the shadow color to 20 % cyan+80 % magenta+80 % yellow+10 % black.