Same down here, but we're just giving it different places to look for and then different fill color in case this is true. So this logical and here means that both of these have to be satisfied in order to execute this command. The first one says that, if the cursor is greater than 100 and x and less than 100 and y, to make the fill this color. And then we have two if statements, one after another. Here in the draw block, we're setting a default fill color. And we're telling it what size to make the display window. First thing we do is tell it to make the background the color that we set up here. Up here, we're setting a color variable with these values. Here's what this program does line by line. Both the circle and square change color depending on the cursor's position. The circle follows the cursor around the display window. This program draws a square and circle to the screen. You can take advantage of this by telling your program to do various things depending on where the cursor is. It also stores the most recent previous position of the cursor in the variables pmouseX and pmouseY. It stores that position inside the variables mouseX and mouseY. Processing stores the position of the cursor as long as the cursor is inside the display window. Instead, I can package it into a module, place that within a shared folder and import it each time I desire to use it.Syntax introduced: mouseX mouseY pmouseX pmouseY mouseClicked() keyPressed boolean elseĪnother fun thing to do is write programs that involve interactivity via the keyboard and the mouse. Putting it all togetherĪs I plan to reuse this code, It is not within my interest to copy-paste each time I wish to apply it. The actions however can be anything the user desires - for instance, if we wanted to translate the position, we could use += X instead. Here deltaX and deltaY represent the relative change of the mouse cursor throughout the drag event. canvas.addEventListener(' mousedown', function (evt) We do this by listening for a mousedown event on our canvas element. The first check we want to make is to see if our user has pressed the mouse button - as without this we do not have a ‘drag’ event. var mouseDown = false, mouseX = 0, mouseY = 0 Mouse Down Here we have a logical ‘is the mouse down?’ mouseDown variable, and the cursor position variables. We begin by defining a set of default variables which our program will update. We can get this by using let canvas = renderer.domElement Default Variables In our case, it is the canvas upon which the THREE libraries is plotting on. As the user ‘drags’, we need to know when they click, move and then release the object - in JavaScript, this is done through the use of event listeners.Įach Event ( mousedown, mousemove and mouseup) is attached to a DOM element within the webpage. To determine what is happening within our program we start by observing a number of mouse events. If you wish to apply the same principles to Data-Driven Documents (d3.js), have a look here The Event Listener If you are new to the THREE.js library, have a browse through the following materials: here The only difference falls upon what goes into the dragAction function at the end. The code discussed within the article can apply to any HTML element, although the emphasis, in this case, is placed upon THREEjs. Although it provides both a orbitalControls and dragControls functions for object or scene manipulation, but what if we want a more personalised response on drag events? - this is what we shall cover here. THREEjs is a cross-over JavaScript library that allows us to unleash the potential of GPU driven graphics within the web browser. The Master Chemical Mechanism - Daniel Ellis 2020
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