Also, I'm familiar with the basics of alpha. I only had major problems when applying them in the traditional way to opengl. Much like problems of smooth() in P3D, it seems like it doesn't actually make the lines transparent, but instead calculates their color based on the initial perspective. Stuff looks good, until you rotate the scene, and opaque lines in the color of the background obscure the scene. In the example of this sketch it isn't really easy to see, but I just tested it with alpha set to 100; zoomed all the way out you can see a difference in the appearance of the lines from different angles.

I'll try to setup a better example & post it to the opengl section of this forum.

import processing.opengl.*;
import javax.media.opengl.*;

float inclination = 0;
float azimuth = 0;

void setup() {

  size(600, 600, OPENGL);

  sphereDetail(150);
  
}

void draw() {
  
  background(255);

  translate(width/2, height/2);
  rotateY(azimuth);
  rotateX(inclination);

  noFill();
  stroke(0, 30);
  sphere(200);

  azimuth = (azimuth + 0.01)%TWO_PI;
  inclination = PI*sin(azimuth);
}
 

Disable the zbuffer, allowing you to draw on top of everything at will. When depth testing is disabled, items will be drawn to the screen sequentially, like a painting. This hint is most often used to draw in 3D, then draw in 2D on top of it (for instance, to draw GUI controls in 2D on top of a 3D interface). Starting in release 0149, this will also clear the depth buffer. Restore the default with hint(DISABLE_DEPTH_TEST), but note that with the depth buffer cleared, any 3D drawing that happens later in draw() will ignore existing shapes on the screen.