Displaying a P3D buffer problems

GoToLoop

Re: Displaying a P3D buffer problems

3 months ago

Anyway, is your main surface using P3D as well?

You can't mix default JAVA2D w/ the other methods in Processing 2+.

In the same way you couldn't mix any other mode w/ OPENGL in previous Processing 1.5.1-.

quarks

Re: Displaying a P3D buffer problems

3 months ago

Any ideas how to overlay my P3D buffer onto my main one?

Are you trying to merge two 3D scenes to create a 'combined' 3D display.

If that is the case then you are not going to be able to do it. The only way is to draw both 3D scenes to the same display buffer/screen. The very act of rendering a 2D scene means you lose all 3D data associated with it and get a 2D image.

tehsage

Re: Displaying a P3D buffer problems

3 months ago

You're right. I was trying to do that.

Then perhaps you could offer a solution? I have a list of data points that model an orbit of one celestial object around another. When I wrote this model in 2D, I drew the ellipse to a buffer and overlayed it so that it wouldn't have to consistently draw the path. I want to do the same for my 3D model.

Any ideas?

quarks

Re: Displaying a P3D buffer problems

3 months ago

While drawing the 3D screen you could use the screenX and screenY functions to translate a 3D coordinate into the corresponding 2D position it whill have when drawn. Then use the 2D coordinates to draw the 2D orbit.

tehsage

Re: Re: Displaying a P3D buffer problems

3 months ago

Perhaps I'm misunderstanding you. I want to draw an ellipse (in 3D, so, I guess a bunch of small spheres?) that represents the path of the object moving.

path = createGraphics(1280, 720);
path.beginDraw();
for(Planet p: planets){
for(Point3d point: p.path){
//path.point((float)point.x, (float)point.y, (float)point.z);
path.pushMatrix();
float x = screenX((float)point.x, (float)point.y, (float)point.z);
float y = screenY((float)point.x, (float)point.y, (float)point.z);
path.point(x,y);
path.popMatrix();
}
}
path.endDraw();

quarks

Re: Displaying a P3D buffer problems

3 months ago

No the misunderstanding is mine - so forget the screenX/screenY stuff what you need is a 3D shape which is effectively an elliptical ring.

What are you using to draw the planets?
Why are you using the Point3D class rather than Processing's PVector class?
Are you using any contributed libraries?

The reason that I ask these questions is that I suspect you could use the Shapes3D library to achieve want you want.

tehsage

Re: Re: Displaying a P3D buffer problems

3 months ago

1) I calculate the path of the planets in the beginning of the program and just draw from list of points. I iterate through a list of planet objects and call it's draw method which just does this:

void draw(){
PVector currLoc = getLocation();
pushMatrix();
translate(currLoc.x, currLoc.y, currLoc.z);
sphere(10);
popMatrix();
}

2) Good point. I fixed my code to utilize PVector

3) No.

Edit: I'm checking out Shapes3D right now. Perhaps the Toroid is what I need? The documentation is a little confusing.
Edit2: Or wait, maybe the PathTube. Idk. I need to read more.
Edit3: It looks like PathTube might be useful although I'm not really following this path generator I need. If I have a list of PVectors, is it possible to use that?

quarks

Re: Displaying a P3D buffer problems

3 months ago

The path generator is any class that imlements I_PathGen e.g.

public class Orbit implements I_PathGen {
public float x(float t) {
// change this to return the calculated x
// position along the path
return 0;
}
public float y(float t) {
// change this to return the calculated y
// position along the path
return 0;
}
public float z(float t) {
// change this to return the calculated z
// position along the path
return 0;
}
}

The t value is the normalised distance along the path so
t            angle round orbit
0            0
0.25      90
0.5      180
0.75      270
1            360

The radius generator is any class that implements I_RadiusGen and it will define the radius of the tube at any point along the orbit. Since you want a constant small radius you can use

public class OrditTubeRadius interface I_RadiusGen {
public float radius(float t) {
return 5; // replace with your own radius
}
public boolean hasConstantRadius() {
return true;
}
Object getController() {
return null;
}
}

Then use the PathTube constructor to create the orbit tube.

tehsage

Re: Re: Displaying a P3D buffer problems

3 months ago

Fantastic! Thank you. I made the PathGen class an inner class for each planet object so that it can correctly calculate the correct x,y, and z values.

My only question now is what exactly do I do with the other two values in the constructor (i.e. nbrSlices and nbrSegments)

I've been setting arbitrary values to see what it does but I'm not sure exactly what I should set it to be.

I'm also running into this weird problem where some lines are drawn that don't seem like they should be there. Here is what I mean.

quarks

Re: Displaying a P3D buffer problems

3 months ago

These control the smoothness of the shape
nbrSlices = number of sections round the orbit
nbrSegments = number of sections round the tube circumference

I'm also running into this weird problem where some lines are drawn that don't seem like they should be there.

Would need to see the actual code for the path generator but I suspect there might be problems with using invalid values of t so in your class try this (repeat for y and z)

public float x(float t) {
t = constrain(t, 0.0, 1.0);
// change this to return the calculated x
// position along the path
return 0;
}

tehsage

Re: Re: Displaying a P3D buffer problems

3 months ago

It looks like I was using degrees instead of radians. I fixed that. Now I'm just running into a physics problem. The planets should speed up as they approach the perihelion and should slow down as they approach the aphelion. It's doing the opposite.....

I wouldn't suppose you have any ideas?

class Planet {
float a, e, phi;
float period, angularVelocity;
List<PVector> path;
int timeStep;
int pointCounter;
Orbit orbit;
Planet(float a, float e, float phi){
this.a=a;
this.e=e;
this.phi=phi;
this.period =(float)( (2 * Math.PI) * Math.sqrt(Math.pow(a, 3) / MU));
this.angularVelocity =(float)( (2 * Math.PI) / period);
this.path = new ArrayList<PVector>();
this.timeStep=10;
this.pointCounter=0;
double r,x,y,z;
float theta;
for (int i = 0; i < period; i += timeStep) {
theta = angularVelocity * i;
theta %= (2 * Math.PI);
r = getRadius(theta);
x = width/2.0 + r*sin(theta)*cos(phi);
y = height/2.0 + r*sin(theta)*sin(phi);
z = r*cos(theta);
path.add(new PVector((float)x,(float)y,(float)z));
}
this.orbit = new Orbit();
}
PVector getLocation(){
return path.get(pointCounter);
}
void incTimeStep(){
pointCounter++;
pointCounter%=path.size();
}
I_PathGen getOrbitPath(){
return orbit;
}
double getRadius(double theta){
return ((a) * (1 - Math.pow(e, 2)) / (1 + (e * Math.cos(theta))));
}
void draw(){
PVector currLoc = getLocation();
pushMatrix();
translate(currLoc.x, currLoc.y, currLoc.z);
sphere(10);
popMatrix();
}
class Orbit implements I_PathGen {
public float x(float t) {
// change this to return the calculated x
// position along the path
float theta = radians(t*360);
float r = (float)getRadius(theta);
float x = width/2.0 + r*sin(theta)*cos(phi);
return x;
}
public float y(float t) {
// change this to return the calculated y
// position along the path
float theta = radians(t*360);
float r = (float)getRadius(theta);
float y = height/2.0 + r*sin(theta)*sin(phi);
return y;
}
public float z(float t) {
// change this to return the calculated z
// position along the path
float theta = radians(t*360);
float r =(float) getRadius(theta);
float z = r*cos(theta);
return z;
}
}
}

It seems like the star is at the wrong foci in the ellipse...

I did run into this problem when I did this in 2D so I added 2*a*e to the x coordinate and it drew it correctly, although I'm not sure this will work here.

Edit: I also welcome cc.

Thank you for all you're doing for me :)

Edit 2: I figured out my problem with the physics. I needed to offset my z-axis. /shrugs

Anyway everything is working great. I also picked up PeasyCam and that helped a lot.

Thank you very much for everything you did, quarks.