How to draw a line with just dots

bjordal

Re: How to draw a line with just dots

3 years ago

this isn't the best way of doing it but it is a way and maybe it can give you some idea :)

void drawLine(float x1,float y1,float x2,float y2){
float angle = atan2(y2-y1,x2-x1);
float currentX = x1;
float currentY = y1;
while(abs(currentX-x2) > abs(cos(angle))){
point(currentX,currentY);
currentX += cos(angle);
currentY += sin(angle);
}
}

EDIT: this is more of the graph way of doing it - it is (as far as i can tell) faster but not as accurate

void drawLine2(float x1,float y1,float x2,float y2){
float dx = x2-x1;
float dy = y2-y1;
if(dx == 0){
for(float i = min(y1,y2);i<max(y1,y2);i+=1){
point(x1,i);
}
return;
}
float k = dy/dx;
float m = y1 -x1*k;
for(float i = min(x1,x2);i<max(x1,x2);i+=1/max(1,abs(k))){
point(i,k*i+m);
}
}

owaunandr..

Re: How to draw a line with just dots

3 years ago

Thanks a lot bjordal, the second one is indeed faster, and it appears to be more accurate to me.

I will post my results here.

owaunandr..

Re: How to draw a line with just dots

3 years ago

How can I modify this code to draw a 3d line using the z-axis ?

Will this have to involve vectors ?

toxmeister

Re: How to draw a line with just dots

3 years ago

You should really check out my toxiclibs, which allows you to handle geometry stuff like this very easily:

import toxi.geom.*;
Line3D l=new Line3D(new Vec3D(-100,-200,-300),new Vec3D(100,200,300));
beginShape(POINTS);
// split line into segments of 10 units distance
// the "null" means we don't yet have a list to store the points in (will be created automatically)
// the "true" means we want to include the first point
for(Vec3D p : l.splitIntoSegments(null,10,true)) {
vertex(p.x,p.y,p.z);
}
endShape();

You could even get rid of the beginShape/endShape block by also using the ToxiclibsSupport utility class:

import toxi.processing.*;
ToxiclibsSupport gfx;
void setup() {
size(400,400,P3D);
gfx=new ToxiclibsSupport(this);
}
void draw() {
...
Line3D l=new Line3D(new Vec3D(-100,-200,-300),new Vec3D(100,200,300));
gfx.points3D(l.splitIntoSegments(null,10,true));
}

Toxiclibs downloads: http://hg.postspectacular.com/toxiclibs/downloads/

Project website: http://toxiclibs.org/

owaunandr..

Re: How to draw a line with just dots

3 years ago

Thanks toxmeister, I will check it out.

owaunandr..

Re: How to draw a line with just dots

3 years ago

toxmeister I am having a little difficulty with the syntax. Can you post a working example ?

toxmeister

Re: How to draw a line with just dots

3 years ago

Oki, this is the "new" syntax finally possible in Processing 1.2 (introduced to Java about 6 years ago)... Makes working with lists/collections much more pleasant & concise. The example below is creating a wireframe cube of 8 edges with each edge/line rendered as dots only. Adjust the "step" variable to create different densities:

import toxi.geom.*;
List<Line3D> edges = new ArrayList<Line3D>();
// cube radius
float s=100;
// step size between points on each edge
float step=20;
void setup() {
size(400,400,P3D);
// define a cube
// 4 front vertices
Vec3D a=new Vec3D(-s,-s,s);
Vec3D b=new Vec3D(s,-s,s);
Vec3D c=new Vec3D(s,s,s);
Vec3D d=new Vec3D(-s,s,s);
// 4 back vertices
Vec3D e=new Vec3D(-s,-s,-s);
Vec3D f=new Vec3D(s,-s,-s);
Vec3D g=new Vec3D(s,s,-s);
Vec3D h=new Vec3D(-s,s,-s);
// create edges
// front
edges.add(new Line3D(a,b));
edges.add(new Line3D(b,c));
edges.add(new Line3D(c,d));
edges.add(new Line3D(d,a));
// back
edges.add(new Line3D(e,f));
edges.add(new Line3D(f,g));
edges.add(new Line3D(g,h));
edges.add(new Line3D(h,e));
// sides
edges.add(new Line3D(a,e));
edges.add(new Line3D(b,f));
edges.add(new Line3D(c,g));
edges.add(new Line3D(d,h));
}
void draw() {
background(0);
translate(width/2,height/2,0);
rotateX(mouseY*0.01);
rotateY(mouseX*0.01);
stroke(255);
// iterate over all edges in the list
for(Line3D e : edges) {
// for each edge compute in-between points every "STEP" units and iterate over them
for(Vec3D p : e.splitIntoSegments(null,step,true)) {
point(p.x,p.y,p.z);
}
}
}

Hth!

bjordal

Re: Re: How to draw a line with just dots

3 years ago

edit: oops- i pressed the comment button instead of the reply to this question... im not sure how i undo this... but anyways this isn't a reply to what tox wrote

Sorry for the late reply but i haven't worked that much with 3d-line equations before...

but just of the bat this is the first that i can think of:

void drawLine3D(float x1,float y1,float z1,float x2,float y2,float z2){
float dx = x2-x1;
float dy = y2-y1;
float dz = z2-z1;
float k1 = dy/dx;
float m1 = y1 -x1*k1;
float k2 = dz/dx;
float m2 = z1-x1*k2;
for(float i = min(x1,x2);i<max(x1,x2);i+=1/max(1,abs((max(k1,k2))))){
point(i,k1*i+m1,k2*i+m2);
}
}

owaunandr..

Re: How to draw a line with just dots

3 years ago

bjordal thanks I can get your code to run.

I tried toxi's and Processing is resulting in an error on this line

List<Line3D> edges = new ArrayList<Line3D>();

any ideas ?

bjordal

Re: Re: How to draw a line with just dots

3 years ago

nope, haven't worked with the library he is using...

PhiLho

Re: Re: How to draw a line with just dots

3 years ago

I assume you have installed the toxiclibs. You also need Processing 1.2.1 (or 018x) as 1.1 and before doesn't allow this syntax.

owaunandr..

Re: How to draw a line with just dots

3 years ago

thanks phil.ho i am using 1.09 expert i will d/l 1.2.. I have toxilibs installed but I will install it in the P1.2 library folder

toxmeister

Re: Re: How to draw a line with just dots

3 years ago

Owaun, I already pointed out this requirement in my post above... You can also use the older, untyped syntax (without the "<TypeName>" stuff), but then will have to cast objects back into Line3D within the for() loop...

bjordal

Re: How to draw a line with just dots

3 years ago

Ok this is actually a response to owaunandrew's pm to me but basically my code didn't take care of special cases but this should do it...

on a related note, why are PMs non-formated? It's really annoying in a programming forum..........

void drawLine3D(float x1,float y1,float z1,float x2,float y2,float z2){
float dx = x2-x1;
float dy = y2-y1;
float dz = z2-z1;
float k1 = dy/dx;
float m1 = y1 -x1*k1;
float k2 = dz/dx;
float m2 = z1-x1*k2;
if(dx == 0){
if(dz == 0){
for(float i = min(y1,y2);i<max(y1,y2);i+=1){
point(x1,i,z1);
return;
}
}
k1 = dy/dz;
m1 = y1 -z1*k1;
for(float i = min(z1,z2);i<max(z1,z2);i+=1/max(1,abs(k1))){
point(x1,k1*i+m,i);
}
return;
}
for(float i = min(x1,x2);i<max(x1,x2);i+=1/max(1,abs((max(k1,k2))))){
point(i,k1*i+m1,k2*i+m2);
}
}

owaunandr..

Re: How to draw a line with just dots

3 years ago

Thanks bjordal that works great!

void drawLine3D(float x1,float y1,float z1,float x2,float y2,float z2){
float dx = x2-x1;
float dy = y2-y1;
float dz = z2-z1;
float k1 = dy/dx;
float m1 = y1 -x1*k1;
float k2 = dz/dx;
float m2 = z1-x1*k2;
if(dx == 0){
if(dz == 0){
for(float i = min(y1,y2);i<max(y1,y2);i+=1){
point(x1,i,z1);
return;
}
}
k1 = dy/dz;
m1 = y1 -z1*k1;
for(float i = min(z1,z2);i<max(z1,z2);i+=1/max(1,abs(k1))){
point(x1,k1*i+m1,i);
}
return;
}
for(float i = min(x1,x2);i<max(x1,x2);i+=1/max(1,abs((max(k1,k2))))){
point(i,k1*i+m1,k2*i+m2);
}
}