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This example introduces a couple of new things starting on line 13:
float radius = dist(mouseX,mouseY,width/2,height/2);
Here the distance from the mouse pointer to the window center centre is determined (see Pythagoras).
radius = map(radius,0,width,1,4);
The original range is from 0 to the width of the window. The target range is from 1-4. Now radius is transformed from original range to the target range.
Exercise 8
Modify the program so a small smiley orbits around he big smiley, in the direction of the mouse position. -atan2(mouseX - (width / 2),mouseY - (height / 2));
The atan2 function returns the angle in radians at a given coordinate from the 0 point. In this example we shift the 0 point to the centre of the screen by subtracting width/2 from X and height/2 from Y.
Image Credit: wikipediaExercise 8
Create a new program where a simple car follows the mouse on the screen from left to right. The car should be drawn from the side, and include wheels that rotate. You may use the example code to get started.
| Code Block | ||
|---|---|---|
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int rotation;
void setup()
{
size(900, 400); // def. window size
}
void draw()
{
rotation++;
}
void car(int x, int y) {
fill(100);
beginShape();
vertex(0, 0);
vertex(5, -50);
vertex(50, -50);
vertex(70, -80);
vertex(150, -80);
vertex(190, -50);
vertex(265, -45);
vertex(270, 0);
vertex(0, 0);
endShape();
wheel(60, 0);
wheel(210, 0);
}
void wheel(int x, int y) {
int radius = 25;
fill(150);
stroke(0);
strokeWeight(7);
ellipse(0, 0, radius*2, radius*2);
strokeWeight(4);
line(0-radius, 0, 0+radius, 0);
line (0, 0-radius, 0, 0+radius);
noStroke();
}
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Possible Solution:
| Code Block | ||||||
|---|---|---|---|---|---|---|
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int rotation;
boolean forward = true;
int xScale = 1;
void setup()
{
size(900, 400);
}
void draw()
{
background(255);
int mouseMovement = mouseX-pmouseX; //pmousex gives us our mouse x value from the last frame. Subtracting from the current position give us the distance moved per frame
if (mouseMovement<0) { // if the movement is negative, then we flip everthing backwards with a negative xcale
xScale = -1;
}
if (mouseMovement>0) { // if the movement is positive, then our xscale is positive
xScale = 1;
}
rotation+= abs(mouseMovement);
car(mouseX, height/2);
}
void car(int x, int y) {
pushMatrix();
translate(x, y);
scale(xScale, 1);
fill(100);
beginShape();
vertex(0, 0);
vertex(5, -50);
vertex(50, -50);
vertex(70, -80);
vertex(150, -80);
vertex(190, -50);
vertex(265, -45);
vertex(270, 0);
vertex(0, 0);
endShape();
wheel(60, 0);
wheel(210, 0);
popMatrix();
}
void wheel(int x, int y) {
int radius = 25;
fill(150);
stroke(0);
pushMatrix();
translate(x, y);
rotate(radians(rotation));
strokeWeight(7);
ellipse(0, 0, radius*2, radius*2);
strokeWeight(4);
line(0-radius, 0, 0+radius, 0);
line (0, 0-radius, 0, 0+radius);
noStroke();
popMatrix();
}
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