line() not affected by lights()

Programming Questions

jaeger83

line() not affected by lights()

in Programming Questions • 3 years ago

Hi all,

It appears that lines in 3D space (P3D / OPENGL) are not affected by lighting methods like directionalLight().

Is this true? If so why? And what would anyone recommend as workaround? or do I need to alter another parameter to get lights() and line() to work together. Here is a quick demo:

size(100, 100, P3D);
background(0);
noStroke();
spotLight(51, 102, 126, width/2, 0, 0, 0, 0, -1, PI/2, 2);
directionalLight(255, 0, 67, -1, 0, 0);
translate(width/2, height/2, -100);
sphere(30);
stroke(255);
line(0,0,0,100,100,100);

Thanks

Replies(14)

kooogy

Re: line() not affected by lights()

3 years ago

replace the line with a very thin quad?

jaeger83

Re: line() not affected by lights()

3 years ago

Thanks kooogy for the speedy response,

I'm pretty new to 3D. I've not really used quads before, how would they work in 3D as there is no z value, like line()? I have replaced my lines with 3D primitive boxes and it works ok. I imagine a quad might be an easier operation than a box. Here is the code:

//line(sx,sy,sz, ex,ey,ez);
fill(c);
pushMatrix();
translate(sx,sy,sz);
box(sx-ex,sy-ey,sz-ez);
popMatrix();

Thanks in advance

kooogy

Re: line() not affected by lights()

3 years ago

sorry, i forgot processing had a quad() method.

i meant QUAD in the opengl sense, which is actually beginShape:

beginShape(QUADS);
vertex(a, b, c); // these values left as an exercise 8)
vertex(d, e, f);
vertex(g, h, i);
vertex(j, k, l);
endShape();

see http://processing.org/reference/beginShape_.html

cedrickie..

Re: line() not affected by lights()

3 years ago

if it were that easy. how would you replace a line with a quad? a line can be described by 2 points. but when using a quad you need some calculation to get the points.

kooogy

Re: line() not affected by lights()

3 years ago

just make the first two points the start and the last two points the end. there's a slight chance it'll draw nothing but...

(oh, i can see this now...)

kooogy

Re: line() not affected by lights()

3 years ago

umm, could've sworn i just posted then, about how to just use the start pos for first two vertices and the end pos for the last two. can't see it.

in the meantime, i just tried it and it looks identical to the first version...

jaeger83

Re: line() not affected by lights()

3 years ago

thanks for the help kooogy, i'll try out that method.

jaeger83

Re: line() not affected by lights()

3 years ago

thank you all for your help. beginShape() seems to have done the trick, although unfortunately beginShape(LINES) didn't which would have been better. now to work on my lighting skills...

kooogy

Re: Re: line() not affected by lights()

3 years ago

can you post what you did in the end - i couldn't get it to work

jaeger83

Re: line() not affected by lights()

3 years ago

beginShape();
vertex(sx,sy,sz);
vertex(sx+1,sy+1,sz+1);
vertex(ex,ey,ez);
vertex(ex+1,ey+1,ez+1);
endShape(CLOSE);

the second and fourth vertex (lines 3 & 5) could do with tightening so only necessary values was adjusted instead of automatically all three. but i'm only making 1px lines so it doesn't have too much effect on the final outcome.

hope that helps

Jack Kern

Re: line() not affected by lights()

3 years ago

Here's a working example that allows for line width as well.

It relies on the Vector3 class in my caffeine library, but you can just copy the code from the source on github if you don't want to install the library. It can be found here:

http://github.com/ElectricJack/caffeine/blob/master/src/caffeine/math/Vector3.java

I'm still working on my documentation, it's not really any better than the file itself, but here's a link to it's java doc anyways:

http://www.jackkern.com/caffeine/reference/caffeine/math/Vector3.html

import caffeine.math.Vector3;
Vector3 start = null;
Vector3 end = null;
Vector3 view = new Vector3( 0, 0, 1 );
// ----------------------------------------------------------------------------------- //
void setup()
{
size(400,400,P3D);
perspective();
start = new Vector3( width/2, height/2, -10 );
end = new Vector3( width/2, height/2, -10 );
}
// ----------------------------------------------------------------------------------- //
void draw()
{
background(0);
fill(255);
noStroke();
pointLight(51, 102, 126, width/2, height/2, 0);
end.setXY( mouseX, mouseY );
litLine( start, end, 5.0f, view );
}
// ----------------------------------------------------------------------------------- //
void litLine( Vector3 v0, Vector3 v1, float lineWidth, Vector3 viewVector )
{
Vector3 offset = v1.sub( v0 );
offset.nrmeq();
Vector3 right = offset.cross( viewVector );
right.nrmeq();
right.muleq( lineWidth );
Vector3 nrm = viewVector.mul( -1 );
beginShape( QUADS );
normal ( nrm.x, nrm.y, nrm.z );
vertex ( v1.x, v1.y, v1.z );
normal ( nrm.x, nrm.y, nrm.z );
vertex ( v0.x, v0.y, v0.z );
normal ( nrm.x, nrm.y, nrm.z );
vertex ( v0.x + right.x, v0.y + right.y, v0.z + right.z );
normal ( nrm.x, nrm.y, nrm.z );
vertex ( v1.x + right.x, v1.y + right.y, v1.z + right.z );
endShape();
}

Hope that helps a bit!

http://www.jackkern.com
http://www.twitter.com/ElectricJack

PhiLho

Re: Re: line() not affected by lights()

3 years ago

Jack, a comment unrelated to your code...
Apparently, you copy/paste code from somewhere which already format it as HTML (I see span tags with Apple-style-span class in them - click on the HTML button of the edit window to see them).
Perhaps it is displayed fine on your computer, but on mine it is hardly readable, with very small text compared to regular text:
<<
Bad code formatting

>>
I suggest you paste the text in a plain text editor (or just open the PDE file in such editor), then copy it again before pasting it here, to remove all unnecessary/unwanted formatting. It would help readability of your messages, at the cost of some additional work for you...

Jack Kern

Re: Re: line() not affected by lights()

3 years ago

I care a lot about the formatting of the code, but alas the forums still apply word-wrap to code snippets which makes almost unreadable at times, hence the tiny font size.

As for my process I just copy / paste from the PDE to here, select the text and make it courier, set it as a code block, and finally change it to the smallest font size if any lines wrap. So I think it's either PDE or the built in text editor adding all the HTML as far as I can tell.

I will admit it is difficult to read at the smallest size, so in the future I'll try to reformat specifically for the forums.

Jack

http://www.jackkern.com
http://www.twitter.com/ElectricJack

jaeger83

Re: line() not affected by lights()

3 years ago

thanks jack.kern. i'm not that up on java but i'll try and install the library. it looks like it should do the job. cheers.

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