Altering the camera view after a triangle has been drawn will NOT change the view of the triangle, it will only affect the next triangle drawn.

Effectively you have

draw triangle 1
move camera A
draw triangle 2
move camera B
...

So once triangle 1 has been drawn then any 'move camera' that happens later does not affect it.

The solution involves storing the vetex positions and fill colours for every triangle then in draw -

1. clear the screen
2. move camera
3. create a new triangle every 10 frames
4. draw ALL triangles created so far

The following code is adapted from your own but uses the ArrayList and PVector classes to remember the triangles created

1. import processing.opengl.*;
2. 
   
3. int y= height/2;
4. int z= 200;
5. int x= width/2;
6. ArrayList<PVector> t3 = new ArrayList<PVector>();
7. 
   
8. void setup(){
9.   size(1440, 900, OPENGL);
10.   background(200);
11. }
12. 
    
13. void draw() {
14.   background(255); // clear the screen
15.   float xpos = width/2;
16.   float ypos = height/2;
17.   float zpos = -100;
18.   camera(x, y, z, width/2, height/2, 0, 0, -1, 0);
19.   x++;
20.   z--;
21.   // Calculate a new triangle every 10 frames
22.   if (frameCount%10==0) {
23.     t3.add(new PVector(xpos, height/2, 0));
24.     t3.add(new PVector(xpos+random(-500, 500), height/4+random(-200, height-200), zpos+random(-50, 150)));
25.     t3.add(new PVector(xpos+random(-500, 500), height/4+random(-200, height-200), zpos+random(-50, 150)));
26.     t3.add(new PVector(random(20, 150), random(20, 50), random(0, 20))); // fill color
27.   }
28. 
    
29.   // draw ALL the triangles created so far
30.   for (int i = 0; i < t3.size(); i+= 4) {
31.     stroke(200, 100, 40, 25);
32.     fill(t3.get(i+3).x, t3.get(i+3).y, t3.get(i+3).z, 100);
33.     beginShape(TRIANGLES);
34.     vertex(t3.get(i).x, t3.get(i).y, t3.get(i).z);
35.     vertex(t3.get(i+1).x, t3.get(i+1).y, t3.get(i+1).z);
36.     vertex(t3.get(i+2).x, t3.get(i+2).y, t3.get(i+2).z);
37.     endShape(CLOSE);
38.   }
39. }