Coordinate values arent stored in processing

I really have no idea why the x and y values wont go to the drawLines function

float x, x1, x2;
float y, y1, y2;
float rad; //radius
int lines = 30; //number of lines
int colorNumber = 1;

void setup() {
background(#FFFFFF);
size (800, 600);
rad = 8;
}

void draw() {
}


This creates the three dots or vertices of the mathematical envelope

void mouseClicked() {
float x = mouseX;
float x1 = mouseX;
float x2 = mouseX;
float y = mouseY;
float y1 = mouseY;
float y2 = mouseY;
if (colorNumber == 1) {
fill(#9393ff);
ellipse(x, y, rad, rad);
} else if (colorNumber == 2) {
fill(#FF9393);
ellipse(x1, y1, rad, rad);
} else if (colorNumber == 3) {
fill(#93ff93);
ellipse(x2, y2, rad, rad);
}
}


This is supposed to draw the envelope using the coordinates of the vertices

void drawLines(int numLines) {
for (int i = 0; i < numLines; i = i + 1) {
float x = mouseX;
float x1 = mouseX;
float x2 = mouseX;
float y = mouseY;
float y1 = mouseY;
float y2 = mouseY;
float t = (float) i/(numLines-1);
float startX = x + t * (x1 - x);
float startY = y + t * (y1 - y);
float endX = x1 + t * (x2 - x1);
float endY = y1 + t * (y2 - y1);
line (startX, startY, endX, endY);
}
}

void mouseReleased() {
colorNumber++;
if (colorNumber == 4) {
colorNumber = 1;
}
println(colorNumber);
}

void keyPressed() {
if (keyPressed == true) {
background(#FFFFFF);
}
}


this last stuff just tells the code if you press a key, it will reset the backround

x

y

mouseX

drawLines

drawLines

processing

1 Answer
1

I understand your intention with using mouseX and mouseY to specify the coordinates of one of the 3 points of the envelope on click. The current issue is that all 3 points are being set to the same coordinate with each click. You need to introduce a variable to keep track of which coordinate to set on-click, such that only one pair is set. Then, only once all 3 coordinates are set, drawLines() can be called.

I propose the following:

Introduce 2 variables, one to keep track of which point is being modified; the other an array of PVectors (just to make it cleaner).

int index = 0;
PVector coords = new PVector[3];


Modify mouseClicked() to include the following:

void mouseClicked() {

ellipse(mouseX, mouseY, 8, 8);
coords[index] = new PVector(mouseX, mouseY);
index += 1;
if (index == 3) {
drawLines(lines);
}
index %= 3;
}


drawLines() becomes:

void drawLines(int numLines) {

for (int i = 0; i < numLines; i = i + 1) {
x = coords[0].x;
x1 = coords[1].x;
x2 = coords[2].x;
y = coords[0].y;
y1 = coords[1].y;
y2 = coords[2].y;
float t = (float) i / (numLines - 1);
float startX = x + t * (x1 - x);
float startY = y + t * (y1 - y);
float endX = x1 + t * (x2 - x1);
float endY = y1 + t * (y2 - y1);
line(startX, startY, endX, endY);
}
}


Finally, since your drawing on a black background, and the default stroke colour is black, use strokeColour() to change the colour of the lines so that you can see the envelope once its drawn.

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