virtual wind vane

Programming Questions

theguilty..

in Programming Questions • 9 months ago

i m creating a virtual wind vane on processing using a potentiometer .Using an Arduino for the same .

So the data to the processing program would be a number between 0 and 360 ( 0 corresponds to north exact ).

Say 0 is North exactly ,so a line starting from origin will point to 0 on a background picture of a degree wheel Im using .

I want the line to rotate by an angle according to the incoming data .

One way of doing this is to find the co-ordinates where i want the line to end on the picture and use switch() .But this makes the program too long .....imagine 360 cases .

Please tell me if u have an alternate idea to implement this .I hav included a sample code using switch() that I tried out and also the picture.
Thanks!!!

int i=0;
PImage img;

void setup()
{
size(500,500);
img = loadImage("degree-wheel.png");
}

void draw()
{
println(mouseX);
println(mouseY);
   image(img, 0, 0);
   i++;
   drawNow();
   delay(1000);
}

   void drawNow()
{
    if(i>4)
    {
     i=0;
    }
    switch(i)
{
case 1:
    line(250, 250, 249, 5);
     break;
case 2:
    line(250, 250, 292, 9);
     break;
    case 3:
    line(250, 250, 372, 38);
     break;
    case 4:
    line(250, 250, 407, 62);
     break;
}
}

Replies(2)

PhiLho

Re: virtual wind vane

9 months ago

I see a delay(1000); in your code.
Don't use that, it makes the sketch unresponsive.
You can change the frameRate() if you want to slow things down. A more sophisticated way uses miliis() tests in draw().

To answer your question, you need to look into Trigonometry.

B_Free

Re: virtual wind vane

9 months ago

Since I assume you're wanting the line to be drawn the same length no matter which way it's pointing, I recommend you start by making a variable called length.

Since I also assume that your line is always going to start in the same place (the center of your degree wheel) you can also store that as a variable, then the only thing you need then are the X,Y coordinates of the end point.

By fiddling around with Cosine, Sine and hypotenuse, you'll find that for any angle you get from the arduino (we'll call the angle Theta)...
the X coordinate of the ending point will be: sin(Theta) * length
the Y coordinate of the ending point will be: cos(Theta) * length

Although when you program this you'll have to tweak it a little! The equations above assume the point (0,0) is at the center of your screen and of course it's really the top-left corner of your sketch window.
Also you'll want to check the reference page to make sure the sin() and cos() use degrees rather than radians.

Hope this helps, your program sounds fun!

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