Very Basic Coding Question..

Programming Questions

ddalgibba..

in Programming Questions • 1 year ago

Hello...

I'm very new to Processing and I'm having trouble trying to rotate my drawing on the Y-axis...

Basically, I'm trying to get the fish to flip over when it gets to the left side of the window.

I have:

import processing.opengl.PGraphicsOpenGL;
int fishX = 247;
int fishY = 138;
int x;
int changeX = 1;
void setup() {
background(231, 253, 255);
size(800, 400, OPENGL);
smooth();
}
void draw() {
x = x + changeX;
int newWid = width-fishX;
translate (newWid-x, height/2-fishY/2);
if (x < 0 || x > width-fishX) {
changeX = changeX * -1;
if (x < 0) {
rotateY(PI);
}
else {
rotateY(0);
}
}
fish(); }

while fish() is just a method I created to draw my fish..

My code isn't working.. the fish just bounces off the left wall and continues backwards....

What am I doing wrong? Do I need push and popMatrix()?

I know it probably isn't the most efficient way to do this... But I just want it to work... T_T

Thank you!

Replies(4)

jbum

Re: Very Basic Coding Question..

1 year ago

You current code isn't working, because transformations, such as rotation, are reset at the beginning of each call to draw(). In your current code, you are only rotating when the fish hits the wall, and otherwise you are not rotating.

Create a global variable called rot, outside of your draw routine.

float rot = 0;

Change your draw code to always rotate this amount, at the same time you do the translation.

translate (newWid-x, height/2-fishY/2);

rotateY(rot);

Then change this bit

if (x < 0) {

rotateY(PI);

}

else {

rotateY(0);

}

to this:

rot = rot + PI;

ddalgibba..

Re: Very Basic Coding Question..

1 year ago

Thank you so much!

I also have another question..

My fish flips but it flips outside of the window before moving right.

Is there a way to make it flip within the window?

I tried by using push and popMatrix() and tried to translate it to the length of my fish but it doesn't work...

Sorry I am very unfamiliar with Processing..

this is my new draw function:

void draw() {
x = x + changeX;
int newWid = width-fishX;
pushMatrix();
translate (newWid-x, height/2-fishY/2);
rotateY(rot);
if (x < 0) {
rot = rot + PI;
translate(fishX,0);
changeX = changeX * -1;
}
else if (x > newWid) {
rot = rot + PI;
changeX = changeX * -1;
}
fish();
popMatrix();
}

Thanks again!

jbum

Re: Very Basic Coding Question..

1 year ago

On the left side, your fish flips when x < 0. If you want it to flip earlier, use a bigger number than zero. Experiment with different values til you find one that works. The right side is using similar logic, and can be fixed by using a smaller number.

ddalgibba..

Re: Very Basic Coding Question..

1 year ago

but if I use any number greater than 1 (for x <0), my fish doesn't translate.. it just rotates.. creating this weird mirror flickering image... is this because I made a mistake somewhere else on my code?

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