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Drawing Bézier curves

From: Interactive Data Visualization with Processing

Video: Drawing Bézier curves

The last shape that we're going to learn to draw is a Bezier curve which is a very common function in computer graphics, because it allows you get to get nice smooth flowing lines that are used in a lot of illustrations. For instance, if you work with Adobe Illustrator, you'd be doing a lot of Bezier curves there as well. The format of the Bezier function and Processing is similar to what we've seen already and that you specify what are called anchor points, those are the beginning and end of the curve and the X and Y coordinates for each of those as well as control points which are not drawn, but influence the shape of what does appear, so let me show you how this works with an example.

Drawing Bézier curves

The last shape that we're going to learn to draw is a Bezier curve which is a very common function in computer graphics, because it allows you get to get nice smooth flowing lines that are used in a lot of illustrations. For instance, if you work with Adobe Illustrator, you'd be doing a lot of Bezier curves there as well. The format of the Bezier function and Processing is similar to what we've seen already and that you specify what are called anchor points, those are the beginning and end of the curve and the X and Y coordinates for each of those as well as control points which are not drawn, but influence the shape of what does appear, so let me show you how this works with an example.

First, I'll begin by labeling the drawing, setting the size of the window, turning on anti-aliasing, put in the background color, I'm going to use a relatively neutral color. Let's see what we've got here, okay, pretty neutral gray. Then what I'm going to do. Always, I'm going to turn off the fill, we've seen before leaving that fill on can get some unexpected results. I'm going to draw two curves in this example, so I'll call this one The First Curve and I actually have here The curve itself that'll make sense in the moment.

What I do here is I'm going to change the color that it's draw in. It is kind of a dark red and in this case there is going to be 791F33 and I'm going to give it a strokeWeight of 3 pixels and then the function name is bezier. Now there is technically there's an accent on the first E, but we don't do that here in Processing, so don't insert that, and then I give the coordinates, I gave the X and Y for the first anchor point that's the end of one end of the curve, so this is actually drawn.

In this one, I use 150 as an X and Y coordinates for the first anchor point, then I give the coordinates for the control point associated with it. The control point is not drawn, but it influences the shape. This one I'll give 250 and 50, then we do the control points, which again do not print, don't show, for the second part of the curve this one I'll do 100 and 150; and then I give the coordinates for the end of the curve which is drawn 250, 150; and we save that and run it, I get a nice little S curve in a dark red.

Now it can be helpful to actually see where the control points are and the lines associated with them, so I'm going to add separate code to draw where those lines would be, but normally you wouldn't, but it's helpful for this particular purpose. So I'm going to add it right here under the control points and what I'm going to do there is I'm going to change the color of the stroke to a much lighter color, I am going to make them slightly lighter in weight, so they're going to be only 2 pixels thick and then I'm just going to use the line function, and the first one starts at hundred, so 100 over 50 down and 250 over, 50 down.

The second line that I'm going to draw just moved over slightly. All right, and now when I draw that, and by the way I put them above the curve, because I want them to be drawn underneath it, so I save it and I run that and now you can see where the control points are and how they influence the shape of the curve that they sort of twist it around with a lever. To make this clear, I'm going to now draw a second curve and its control points and I come back here and I'll just copy this information, the Second Curve.

And for the Second Curve, it's control points, I'll leave in the same color in the same weight, they are going to be in different places though, 350 and 75 and then at 500 and 25. The second control line I'm going to have at 350, 125 and then at 500 and down at 175 then the curve I'm going to drawn a slightly different color BA3D49, we'll leave it at three points.

Then it's going to get a different set of coordinates there are 350, 75, 500, 25, 175, oh I've lost something in there 350, 75, 525, oh there we go. I need to have another 500, 175 in there and then I can finish up with 350 and 125.

All right, and then I Save that and Run that and now you see two very different curves and it has a lot to do with the control, you see how the control ones on the second one are pointing in on the same direction and they are twisting it, arching it at in that particular direction. And again this gives you some interesting possibilities for drawing smooth lines and also for being able to move points along lines in later sketches. And so that, the Bezier curve, is the final shape that we're going to cover in our introduction here and how to work with Processing for interactive data visualization.

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This video is part of

Image for Interactive Data Visualization with Processing
Interactive Data Visualization with Processing

72 video lessons · 12730 viewers

Barton Poulson
Author

 
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  1. 3m 16s
    1. Welcome
      58s
    2. What you should know
      1m 22s
    3. Using the exercise files
      56s
  2. 11m 51s
    1. Overview of data visualization
      11m 51s
  3. 11m 53s
    1. Installing Processing
      3m 38s
    2. Overview of Processing
      4m 5s
    3. Exploring libraries
      4m 10s
  4. 1h 1m
    1. Basic setup
      7m 31s
    2. Drawing points
      4m 37s
    3. Drawing lines
      5m 6s
    4. Drawing ellipses and circles
      5m 24s
    5. Drawing arcs
      6m 54s
    6. Drawing rectangles and squares
      4m 58s
    7. Drawing quadrangles
      3m 25s
    8. Drawing triangles
      2m 55s
    9. Drawing polygons
      3m 37s
    10. Drawing simple curves
      4m 54s
    11. Drawing complex curves
      6m 46s
    12. Drawing Bézier curves
      5m 38s
  5. 54m 3s
    1. Introduction to variables
      10m 44s
    2. Understanding variable scope
      6m 53s
    3. Modifying variables
      9m 8s
    4. Creating arrays
      9m 53s
    5. Modifying arrays
      6m 37s
    6. Creating strings
      7m 3s
    7. Modifying strings
      3m 45s
  6. 1h 2m
    1. Incorporating randomness
      7m 59s
    2. Using Perlin noise
      4m 24s
    3. Shuffling with Java
      3m 30s
    4. Specifying line attributes
      8m 2s
    5. Changing placement modes
      5m 45s
    6. Understanding color attributes and functions
      4m 16s
    7. Exploring color spaces
      7m 44s
    8. Using color palettes
      7m 5s
    9. Transforming the grid
      8m 38s
    10. Exploring the attribute matrix
      5m 33s
  7. 52m 7s
    1. Building code blocks
      5m 57s
    2. Writing a while loop
      3m 52s
    3. Using for loops
      5m 35s
    4. Creating conditionals
      14m 50s
    5. Working with easing
      10m 51s
    6. Creating spirals
      11m 2s
  8. 18m 55s
    1. Mouse tracking
      3m 54s
    2. Hovering and clicking
      11m 16s
    3. Understanding keyboard interaction
      3m 45s
  9. 27m 32s
    1. Specifying fonts
      6m 43s
    2. Using images
      5m 51s
    3. Playing a video loop
      6m 20s
    4. Exporting video
      3m 47s
    5. Adding sound
      4m 51s
  10. 20m 49s
    1. Creating functions
      11m 48s
    2. Creating classes and objects
      9m 1s
  11. 31m 10s
    1. Using embedded data
      5m 26s
    2. Working with appended text data
      6m 4s
    3. Working with appended tabular data
      10m 26s
    4. Reading XML data
      9m 14s
  12. 48m 17s
    1. Generating dot plots
      11m 11s
    2. Building scatter plots
      10m 0s
    3. Making line plots
      9m 55s
    4. Creating bar charts
      9m 12s
    5. Checking out examples of maps, hierarchies, and networks
      7m 59s
  13. 20m 57s
    1. Introducing some principles of 2D design
      13m 44s
    2. Understanding color theory
      7m 13s
  14. 24m 46s
    1. Interacting with zooming, rotating, and sliding
      6m 26s
    2. Implementing slicing
      6m 47s
    3. Using rollovers
      5m 58s
    4. Introducing the GUI libraries
      5m 35s
  15. 10m 35s
    1. Sharing via OpenProcessing and other sites
      3m 19s
    2. Saving as a desktop application
      2m 42s
    3. Saving as JavaScript
      1m 47s
    4. Saving as an Android application
      2m 47s
  16. 2m 38s
    1. Where to go from here
      2m 38s

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