3D graphics and polygons

General Discussion Other

chitas

in General Discussion • Other • 1 year ago

1. How do you "plot" data points that are generated instead of using the built in functions?

For example, a 3-dimensional array stores the x, y, & z coordinates, which would be fed into a function that graphs

the points.

2. If you generate points from an object, how can they be mapped to polygons, which would then be graphed?

Replies(12)

Chrisir

Re: 3D graphics and polygons

1 year ago

1.
you can use point(), it has 3D : x,y,z
use strokeWeight to make them more thick

2.
use beginShape and vertex which is also 3D

chitas

Re: 3D graphics and polygons

1 year ago

also line() is 3D in itself

Chrisir

Re: 3D graphics and polygons

1 year ago

please show the first 20 lines of your 3-dimensional array

chitas

Re: 3D graphics and polygons

1 year ago

My first approach was to "scan" and store the values in the 3-dim array.

However, I realized that I do not know what the object/image is and therefore, I need the program to do the scanning.

Basically, I want to scan pixels of the image/object such that it can be viewed from far to close at different levels of precision and then graph them.

Thank you again.

void method1(float[][][] lengthCyl)

{
float rotationAngle = 180.0/100;
float heigh = 10.0;
float distance = 10.0;
float rad = 10.0;
float pitchAngle = atan(heigh/distance);
float pitch, rotation, h, yCorrection;
for (int i = 0; i < 100; i++)
{
    pitch = (float)i * pitchAngle/100.0;
    yCorrection = tan(pitch) * distance;
    for (int j = 0; j < 100; j++)
    {
      rotation = rotationAngle * (float)j;
      lengthCyl[i][j][0] = rad * cos(rotation); //x remains the same for changes in pitch
      lengthCyl[i][j][1] = yCorrection + rad * sin(rotation); //y changes for changes in pitch
    }
}
}

Chrisir

Re: 3D graphics and polygons

1 year ago

are you starting from an 2D image of some sort that you load from the hard drive or the internet?

you don't need a 3D array to store a 3D point btw.
that's a misunderstanding.

you could have a 1D array holding PVector as data type

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

thus you would have an array of all your points

// array
PVector[] myPVectors = {
};
size (700, 700, P3D);
// build the array
PVector currentPVector = new PVector(100, 150, 30);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(100, 60, 10);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(210, 110, 110);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
// Show the array
println (myPVectors.length);
stroke (255, 2, 2);
strokeWeight(4);
for (int i = 0; i < myPVectors.length; i++ ) {
point ( myPVectors[i].x, myPVectors[i].y, myPVectors[i].z );
}

or with lines

/** PeasyCam **/
import peasy.*;
// Camera
PeasyCam cam;
// array
PVector[] myPVectors = {
};
void setup() {
size (700, 700, P3D);
cam = new PeasyCam(this, 1440);
// build the array
PVector currentPVector = new PVector(100, 150, -130);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(100, 160, 10);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(150, 110, 10);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(210, 110, 10);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
currentPVector = new PVector(100, 70, 10);
myPVectors = (PVector[]) append(myPVectors, currentPVector);
println (myPVectors.length);
}
void draw () {
background(0);
// Show the array with points
stroke (255, 2, 2);
strokeWeight(4);
for (int i = 0; i < myPVectors.length; i++ ) {
point ( myPVectors[i].x, myPVectors[i].y, myPVectors[i].z );
}
// Show the array with lines
stroke (255, 2, 222);
strokeWeight(1);
for (int i = 0; i < myPVectors.length-1; i++ ) {
line ( myPVectors[i].x, myPVectors[i].y, myPVectors[i].z,
myPVectors[i+1].x, myPVectors[i+1].y, myPVectors[i+1].z );
}
}
//

chitas

Re: 3D graphics and polygons

1 year ago

It would be a 3D image from a file that was generated separately from this or uploaded.

To make a 3D image based on points would be difficult since the 3D points would have to be mapped to a 2D field.

So, it would be easier to have the program figure out the pixels for the image and afterwards it can be manipulated.

Chrisir

Re: 3D graphics and polygons

1 year ago

what do you mean by 3D image?
What data format, SVG?

Chrisir

Re: 3D graphics and polygons

1 year ago

ok, probably you need a kind of image recognition or point / edge detection

maybe there's a library for that but I dunno

http://processing.org/reference/libraries/#computer_vision

chitas

Re: 3D graphics and polygons

1 year ago

Maybe a simple example would be good to start with.

For example, we have a 3D cup as an image/object in the program. (Where can I get such a picture?"

As the mouse moves, the view size - distance between the "camera" and cup changes.

So, the amount of detail needed for the far view would be less and therefore less pixals would be generated.

The example java/examples/3D/Camera/Perspective.pde is basically what I want.

However, how would I "scan" it? Also, since it is a defined object in the example, only its corners need to be defined. But, I want to scan it now, so when the object is not "known" or not a defined object, the whole object would be scanned at different precisions.

PhiLho

Re: 3D graphics and polygons

1 year ago

So you want an implementation of the Level of Detail algorithm. Not sure if Processing library implements that, never heard of that (but I haven't played much with 3D in Processing, yet). Perhaps OpenGL does that automatically.
Note that you need that only if you have lot of objects, or very complex objects going from far away to close of the eye, and really need a speed up from this method.
I think it isn't obvious to implement... Some libraries can take a 3D data model and reduce the number of triangles, which is what you want. I suppose you need to do this reduction up-front (before starting to display the sketch) or in a separate thread, as it can be CPU heavy.

chitas

Re: 3D graphics and polygons

1 year ago

Thank you for your response.

Besides OpenGL, is there a way to do this in JAVA or C++?

Google Maps is similar to what I am trying to do - albeit simpler. At close, trees, houses, and cars are generated and can be seen. But afar, they are not generated at all.