Processing简介
Processing是一种开源编程语言，专门为电子艺术和视觉交互设计而创建，其目的是通过可视化的方式辅助编程教学，并在此基础之上表达数字创意。Processing也指Processing语言的集成开发环境。2001年，MIT媒体实验室的 Casey Reas 和 Benjamin Fry 发起了此计划。
情景 Situation
It is required to develop a program that can evaluate the average speed at any time t, where average speed = ( s(t+△t) - s(t) ) / △t km/h.
In order to do this we take small values of ∆ hours and let ∆ approach zero. This is an example of what the program needs to do: if the time is = 0.2 hours then the average speed of the car is calculated by adding time intervals, 0.01, 0.001, 0.001 h, ...etc. to the time 0.2 h and substitute the new time in equation 2 :
( s(0.2+0.01) - s(0.2) ) / 0.01 = 30 km/h
( s(0.2+0.001) - s(0.2) ) / 0.001 = 29.806 km/h
( s(0.2+0.0001) - s(0.2) ) / 0.0001 = 29.804 km/h
The solution will be reached when the difference between two consecutive results is very small.
任务 Task
- You need to write a Processing program with the sketch size of 500 x 500.
- The initial screen of the program should look like (Figure 1) showing all the time
intervals (t) at the bottom. - If we click on any of these time intervals (value of t), the program should change
the colour of that button and should show the results similar to the example in
figure 2 below. - The results should be calculated using the time interval clicked (t) and the value
of ∆ ranging from 0.1 – 0.00001.
行动 Action
打开Processing编译器，copy以下代码，点击▶️start / 播放按钮。
int[] xArr = {25,125,225,325,425};
String text = "Average speed at (△t) ";
float[] tArr = {0.1,0.01,0.001,0.0001,0.00001};
void setup(){
size(500,500);
background(255);
fill(0,0,255);
textAlign(CENTER);
text("Click any of these time intervals to show the results",250,50);
for(int i=0;i=25 && mouseX<=75 && mouseY>=400 && mouseY<=450) {
fill(255,0,0);
rect(25,400,50,50);
float t = tArr[0];
text(text+t+" = "+averageSpeed(t),250,100);
fill(255);
text(""+t,50,425);
}
else if (mouseX>=125 && mouseX<=175 && mouseY>=400 && mouseY<=450) {
fill(255,0,0);
rect(125,400,50,50);
float t = tArr[1];
text(text+t+" = "+averageSpeed(t),250,150);
fill(255);
text(""+t,150,425);
}
else if (mouseX>=225 && mouseX<=275 && mouseY>=400 && mouseY<=450) {
fill(255,0,0);
rect(225,400,50,50);
float t = tArr[2];
text(text+t+" = "+averageSpeed(t),250,200);
fill(255);
text(""+t,250,425);
}
else if (mouseX>=325 && mouseX<=375 && mouseY>=400 && mouseY<=450) {
fill(255,0,0);
rect(325,400,50,50);
float t = tArr[3];
text(text+t+" = "+averageSpeed(t),250,250);
fill(255);
text(""+t,350,425);
}
else if (mouseX>=425 && mouseX<=475 && mouseY>=400 && mouseY<=450) {
fill(255,0,0);
rect(425,400,50,50);
float t = tArr[4];
text(text+t+" = "+averageSpeed(t),250,300);
fill(255);
text(""+t,450,425);
}
}
float distance(float t){
return 40*pow(t,3)+20*pow(t,2)+17*t;
}
float s = distance(0.2);
float averageSpeed(float t){
return (distance(0.2+t)-s)/t;
}