Hello list,
I'm still at it with the glowing line.  My problem now is that to achieve the 'glow' effect, the code I found must do a get on a PGraphics render context to create a PImage then perform some effects and then render.  The problem is that at the .get stage the created PImage's background is opaque and I cannot seem to find a way to make it transparent.

1.  //lightsaber Glow
2.   lightsaberGlowRC.beginDraw();
3.  lightsaberGlowRC.background(255,255,255,0);
4.   lightsaberGlowRC.strokeWeight(lightsaberGlowStrokeWt); 
5.   lightsaberGlowRC.stroke( unhex(lightsaberGlowClr) );
6.   lightsaberGlowRC.line(ctrX, ctrY, orbitX, orbitY);
7.   lightsaberGlowRC.endDraw();
8.   lightsaberGlowImage = lightsaberGlowRC.get(0, 0, lightsaberGlowRC.width, lightsaberGlowRC.height);
9.   lightsaberGlowImage.resize(0,width/2);
10.   lightsaberGlowImage.filter(BLUR,2);
11.   lightsaberGlowImage.resize(0,width);
12.  
13. image(lightsaberGlowImage,0,0);

I found numorous solutions on the list but I cannot seem to get any of them to work for me.  Any thoughts?


My complete code:

1. import processing.opengl.*;
2. import javax.media.opengl.*;
3. PImage lightsaberGlowImage;
4. //lightsaber Core
5. PGraphics lightsaberCoreRC; //render context
6. //variables
7. String lightsaberCoreClr;
8. int lightsaberCoreStrokeWt;
9. //lightsaber Glow
10. PGraphics lightsaberGlowRC; //render context
11. //variables
12. String lightsaberGlowClr;
13. int lightsaberGlowStrokeWt;
14. //Radar movement variables
15. float orbit, orbitX, orbitY, ctrX, ctrY;
16. float radarRadius;
17. int rotationDur = 20;
18. //intersecting circle
19. float circleX, circleY, circleRadius;
20. void setup() {
21.   size(500,500, OPENGL);
22.   orbitX = 0.0;
23.   orbitY = 0.0;
24.   ctrX = width/2.0;
25.   ctrY = height/2.0;
26.   circleX = 400.0;
27.   circleY = 400.0;
28.   circleRadius = 30.0;
29.   radarRadius= 500.0;
30.   //lightsaberCore
31.   lightsaberCoreRC = createGraphics(width, height, JAVA2D); //initialize render context like size()
32.   //initialize variables
33.   lightsaberCoreClr = "FFFFFFFF";
34.   lightsaberCoreStrokeWt = 5;
35.   //initial settings like setup()
36.   lightsaberCoreRC.beginDraw();
37.     lightsaberCoreRC.background(255, 255, 255, 0);
38.   lightsaberCoreRC.smooth();
39.   lightsaberCoreRC.endDraw();
40.   //lightsaber Glow
41.   lightsaberGlowRC = createGraphics(width, height, JAVA2D); //initialize render context like size()
42.   lightsaberGlowClr = "FF00FF00"; //green
43.   lightsaberGlowStrokeWt = lightsaberCoreStrokeWt*3;
44.   lightsaberGlowRC.beginDraw();
45.   lightsaberGlowRC.background(255,255,255,0);
46.   lightsaberGlowRC.smooth();
47.   lightsaberGlowRC.endDraw();
48. }
49. void draw() {
50.   background(255);
51.   //rotate radar
52.   if(frameCount>0.0)orbit = map((frameCount/24.0)%rotationDur, 0.0, rotationDur, 0.0,  TWO_PI);
53.   orbitX = ctrX + (cos(orbit) * radarRadius );
54.   orbitY = ctrY + (sin(orbit) * radarRadius );
55.  
56.   //lightsaberCore
57.   lightsaberCoreRC.beginDraw();
58.   lightsaberCoreRC.background(255, 255, 255, 0);
59.   lightsaberCoreRC.strokeWeight(lightsaberCoreStrokeWt); 
60.   lightsaberCoreRC.stroke( unhex(lightsaberCoreClr) );
61.   lightsaberCoreRC.line(ctrX, ctrY, orbitX, orbitY);
62.   lightsaberCoreRC.endDraw();
63.  
64.   //lightsaber Glow
65.   lightsaberGlowRC.beginDraw();
66.  lightsaberGlowRC.background(255,255,255,0);
67.   lightsaberGlowRC.strokeWeight(lightsaberGlowStrokeWt); 
68.   lightsaberGlowRC.stroke( unhex(lightsaberGlowClr) );
69.   lightsaberGlowRC.line(ctrX, ctrY, orbitX, orbitY);
70.   lightsaberGlowRC.endDraw();
71.   lightsaberGlowImage = lightsaberGlowRC.get(0, 0, lightsaberGlowRC.width, lightsaberGlowRC.height);
72.   lightsaberGlowImage.resize(0,width/2);
73.   lightsaberGlowImage.filter(BLUR,2);
74.   lightsaberGlowImage.resize(0,width);
75.  
76. image(lightsaberGlowImage,0,0);
77. //for intersect detection
78. if (circleLineIntersect(orbitX, orbitY, ctrX, ctrY, circleX, circleY, circleRadius) == true) {
79.     fill(255, 0, 255, 200);
80.   }
81.   else {
82.     fill(255, 128, 0, 200);
83.   }
84. ellipseMode(RADIUS);
85.   ellipse(circleX, circleY, circleRadius, circleRadius);
86.   /////////////
87.   image(lightsaberCoreRC, 0, 0);
88. }
89. boolean circleLineIntersect(float x1, float y1, float x2, float y2, float cx, float cy, float cr ) {
90.   float dx = x2 - x1;
91.   float dy = y2 - y1;
92.   float a = dx * dx + dy * dy;
93.   float b = 2 * (dx * (x1 - cx) + dy * (y1 - cy));
94.   float c = cx * cx + cy * cy;
95.   c += x1 * x1 + y1 * y1;
96.   c -= 2 * (cx * x1 + cy * y1);
97.   c -= cr * cr;
98.   float bb4ac = b * b - 4 * a * c;
99.  
100.   //println(bb4ac);
101.  
102.   if (bb4ac < 0) {  // Not intersecting
103.     return false;
104.   }
105.   else {
106.     
107.     float mu = (-b + sqrt( b*b - 4*a*c )) / (2*a);
108.     float ix1 = x1 + mu*(dx);
109.     float iy1 = y1 + mu*(dy);
110.     mu = (-b - sqrt(b*b - 4*a*c )) / (2*a);
111.     float ix2 = x1 + mu*(dx);
112.     float iy2 = y1 + mu*(dy);
113.  
114.     // The intersection points
115.     //ellipse(ix1, iy1, 10, 10);
116.     //ellipse(ix2, iy2, 10, 10);
117.     
118.     float testX;
119.     float testY;
120.     // Figure out which point is closer to the circle
121.     if (dist(x1, y1, cx, cy) < dist(x2, y2, cx, cy)) {
122.       testX = x2;
123.       testY = y2;
124.     } else {
125.       testX = x1;
126.       testY = y1;
127.     }
128.     
129.     if (dist(testX, testY, ix1, iy1) < dist(x1, y1, x2, y2) || dist(testX, testY, ix2, iy2) < dist(x1, y1, x2, y2)) {
130.       return true;
131.     } else {
132.       return false;
133.     }
134.   }
135. }