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OpenGL and Alpha (Read 979 times)
kersten
OpenGL and Alpha
Dec 13th, 2008, 2:53pm  
Figured out another Problem using OpenGL:
Using several ellipse objects (fill with alpha) orientated along the z-axis and rotating them they only appear to be transparent from the front.
Trying the P3D renderer everything works fine.

Any suggestions?

Here's a code snippet:

Code:


import processing.opengl.*;

float spacer = 10.0;

void setup(){

  size(400,400, OPENGL);  

  fill(255);
  stroke(80);  

  rectMode(CENTER);
  smooth();
}

void draw(){

  background(0);

  pushMatrix();
    translate(width/2,height/2);
    rotateY(frameCount*PI/60);
    strokeWeight(2);

  for(int i = 0; i <= 10; i++){
    pushMatrix();
	noStroke();
	fill(30,100,20,50);
	translate(0,0,-50+(i*spacer));
    pushMatrix(); 
	translate(0,0);  
	stroke(200,90,44); 
	rotate(radians(60));
	ellipse( 0, 0, 50, 50);
    popMatrix();

    popMatrix(); 
  }
  popMatrix();  
}

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sw01
Re: OpenGL and Alpha
Reply #1 - Dec 13th, 2008, 5:36pm  
Try changing the order in which the objects are drawn.  

That hack worked for me, but I'm sure there is a much better solution out there - OPENGL expert, anyone?
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frankBerg
Re: OpenGL and Alpha
Reply #2 - Dec 13th, 2008, 6:43pm  
this should work

hint(ENABLE_DEPTH_SORT);

fffff
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kersten
Re: OpenGL and Alpha
Reply #3 - Dec 13th, 2008, 7:23pm  
Wohooo! Works like a charm!
Thanks.
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sw01
Re: OpenGL and Alpha
Reply #4 - Dec 13th, 2008, 7:55pm  
Oh, hint(ENABLE_DEPTH_SORT); broke mine Sad
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