Calculating points on a curve

Making my way through the Calculating points on a curve recipe from the Processing 2 Creative programming cookbook source code on GitHub.

In this recipe I learned how to use the bezierPoint and curvePoint functions to calculate points on curves and splines. bezierPoint uses five parameters. The first four are coordinates for the anchor and control points (40, 120, 300, 600) of the bezier curve and the fifth is parameter is a number between 0 and 1. This Sketch uses noise to generate the number. curvePoint works in a similar way to bezierPoint, except it’s for Catmull-Rom splines. I also learned how to use:

  • the first four parameters and the last four parameters of the bezier curve’s anchor points as the parameters for the red lines used to simulate the curve’s ‘handle’
  • noise to animate the point as it’s moved along the curve
  • rectMode to change the location from which the rectangle is drawn. For this example, CENTER is used to specify the first two parameters of each rect (120, 40 and 300, 240) as the shape’s centre point.

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Drawing curves

Making my way through the Drawing curves recipe from the Processing 2 Creative programming cookbook source code on GitHub.

In this recipe I learned how to use the bezier and curve functions to draw Bezier curves and Catmull-rom splines in the display window. For the Bezier curves in this example, 0 and 20 are the coordinates for the first anchor point. 50 and 10 are the coordinates for the first control point. 80 and 100 are the coordinates for the second control point, and the 30 and 200 are the coordinates for the second anchor point. The bezierDetail and curveDetail functions are used to change the detail of the curves and the curveTightness function is used to set the tightness of the curve. Use a value of 0.0 to connect the points of the curve with straight lines and values between -5.0 and 5.0 to create curves with varying tightness.

In this recipe I also learned how to use the translate function with a for loop to create multiple curves and then translate (position) them from left to right (x parameter) at a specified distance apart (20) in the display window. The pushMatrix and the popMatrix functions are also somehow involved in the translation of the curves, but I’m not quite sure how just yet. The Processing 2.0+ reference for these two functions functions provides a description and an example, but I’m not sure when to pop and when to push and why. I guess I’ll play around with them both and figure it out!

Worth noting, since this recipe was created the OpenGL library has been included as part of Processing 2.0. That means you no longer have to import the library. Nice!

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Oh yeah, gradually increasing the tightness of the curve by moving the mouse from left to right (current horizontal coordinate of the mouse) is also pretty cool!

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