Photography

Making the square rotate Let's start by making the square rotate. The first thing we'll need is a variable in which to track the current rotation of the square: var squareRotation = 0.0 ; Now we need to update the  drawScene()  function to apply the current rotation to the square when drawing it. After translating to the initial drawing position for the square, we apply the rotation like this: mat4 . rotate ( modelViewMatrix , // destination matrix modelViewMatrix , // matrix to rotate squareRotation , // amount to rotate in radians [ 0 , 0 , 1 ] ) ; // axis to rotate around This rotates the modelViewMatrix by the current value of  squareRotation , around the Z axis. To actually animate, we need to add code that changes the value of  squareRotation  over time. We can do that by creating a new variable to track the time at which we last animated (let's call it  then ), then adding the followi...

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Matrices can be used to represent transformations of objects in space, and are an important tool to use in visualizations on the Web. This article explores how to create matrices and use them with  CSS3 transforms  and the  matrix3d  transform type. While this article uses CSS3 for the ease of explanations, matrices are a core concept used by many different technologies including WebGL and shaders. This article is also available as an  MDN content kit . The live examples use a collection of  utility functions  availabile under a global object named "MDN". What is a transformation matrix? There are many types of matrices, but the ones we are interested in are the 3D transformation matrices. These matrices consist of a set of 16 values arranged in a 4x4 grid. In JavaScript, it is easy to represent a matrix as an array. The typical starting point is to show the identity matrix. When this matrix is multiplied against another point or matrix then the result...

In the last chapter we made some  basic animations  and got to know ways to get things moving. In this part we will have a closer look at the motion itself and are going to add some physics to make our animations more advanced. Drawing a ball Section We are going to use a ball for our animation studies, so let's first draw that ball onto the canvas. The following code will set us up. < canvas id = " canvas " width = " 600 " height = " 300 " > </ canvas > As usual, we need a drawing context first. To draw the ball, we will create a  ball  object which contains properties and a  draw()  method to paint it on the canvas. var canvas = document . getElementById ( 'canvas' ) ; var ctx = canvas . getContext ( '2d' ) ; var ball = { x : 100 , y : 100 , radius : 25 , color : 'blue' , draw : function ( ) { ctx . beginPath ( ) ; ctx . arc ( this . x , this . y , this . radius , 0 , ...