how to know if a point in 3d is visible or not?

General Discussion Other

miguel.si..

how to know if a point in 3d is visible or not?

in General Discussion • Other • 2 months ago

can somebody tell me how can i know if a point is visible or not

(if existes shapes draw in th top of the point)

i need this because when i select points, i only want to be able to selecte the ones that i can see.

can somebody help me with this task??

:DD

Replies(2)

asimes

Re: how to know if a point in 3d is visible or not?

2 months ago

Unless someone has written a library to do this (I am not too familiar with the Processing libraries) code has to be written to do this. The general idea is:

- Imagine a point in 3D that represents the user (their "eye", as if they had one eye instead of two).

- Imagine that the screen is a 2D plane in front of the user

- If a line from a point to the user intersects the screen then it is visible to the user

There are some 3D to 2D functions in Processing, these may be all you need:

http://processing.org/reference/screenX_.html

http://processing.org/reference/screenY_.html

asimes

Re: how to know if a point in 3d is visible or not?

2 months ago

PVector somePoint = new PVector(0.0, 0.0, 0.0);
float count = 0.0;
void setup() {
size(600, 600, P3D);
}
void draw() {
somePoint.x = cos(count)*600;
count += TWO_PI/500;
background(255);
pushMatrix();
translate(width/2, height/2);
translate(somePoint.x, somePoint.y, somePoint.z);
sphere(10);
popMatrix();
float threeToTwo = screenX(somePoint.x, somePoint.y, somePoint.z);
if (threeToTwo < -300.0 || threeToTwo > 300.0) println("Off Screen");
else println("Visible");
}