just for completeness I show a code that circles the cam; press any key to change lookAt

Anyway, I recommend using the exact positions of the text circles in the image.

put them as 3D values in the cams position.

After that put the next value (next circle) as 3D values in the cams lookAt.

So when you have an array write in draw the following:

1. index ++; // global var
2. if (index-1 >= maxIndex) {
3. index=0;
4. }

the cam pos get from:
arrCircleCenters[i]
cam lookAt get from:
arrCircleCenters[i+1]

to alter speed
instead of index++ try index += 3;

you could lerp between two points (arrCircleCenters[i] and arrCircleCenters[i+1] ) to make it smoother


here the obsolete code, the very last lines (from 146) are interesting;
press any key to change lookAt

1. import shapes3d.utils.*;
2. import shapes3d.org.apache.commons.math.util.*;
3. import shapes3d.org.apache.commons.math.*;
4. import shapes3d.org.apache.commons.math.geometry.*;
5. import shapes3d.*;
6. // =========================================================================
7. // Lamppost
8. int ZentraleStange_XValue = 250; // nach rechts
9. int ZentraleStange_YValue = 330; // nach unten
10. int ZentraleStange_ZValue = -150; // nach hinten
11. // Lamppost
12. int TiefeQuerbalken = 122;
13. // hanging basket
14. int HoeheEinesBlumenkastens = 20;
15. int TiefeEinesBlumenkastens = 122;
16. int BreiteEinesBlumenkastens = 50;
17. //  hanging basket
18. Cone cone;
19. Ellipsoid [] ellipsoid = new Ellipsoid [4];
20. String actualTextMessage = "Use 0,1,2,3 for Camera";
21. String actualTextMessage2 = "Camera circles at constant height";
22. // ==================================================================
23. // Kamerasteuerung:
24. final int CheckCamera_Type_SinusLevel = 0;    // rotates
25. final int CheckCamera_Type_SinusSpirale = 1;  // Spirale
26. final int CheckCamera_Type_SinusMouse = 2;    // Mouse
27. final int CheckCamera_Type_SinusPath = 3;     // Path
28. float Angle = 0.0; // Angle bei Kreis
29. float Height = 330;    // Höhe der Kamera über der Szene
30. int HeightAdd = 2;   // wird bei Spirale zu der Höhe der Kamera addiert
31. float Radius = 70.0;  // Anfangsradius des Kreises
32. // Art des Kameraverhaltens
33. int CheckCamera_Type = CheckCamera_Type_SinusSpirale;
34. // Camera
35. int LookAtX;
36. int LookAtY;
37. int LookAtZ;
38. // Camera with Path Behaviour (CheckCamera_Type = 3)
39. boolean boolGoesOnAPath = true;
40. float PathValue;
41. float PathValueMaximal = 95.0;
42. // ==========================================================
43. void setup() {
44.   size(600, 600, P3D);
45.   // Grass
46.   //  initGrass();
47.   // LookAt
48.   LookAtX=ZentraleStange_XValue;
49.   LookAtY= ZentraleStange_YValue;
50.   LookAtZ= ZentraleStange_ZValue;
51.   // hanging baskets
52.   for (int i = 0; i < ellipsoid.length; i = i+1) {
53.     ellipsoid[i] = new Ellipsoid(this, 40, 40);
54.     ellipsoid[i].drawMode(Shape3D.SOLID);
55.     ellipsoid[i].setRadius(12, 7, 12);
56.     ellipsoid[i].moveTo(ZentraleStange_XValue, ZentraleStange_YValue+40, ZentraleStange_ZValue-(TiefeQuerbalken/2)+5);
57.   }
58.   ellipsoid[0].moveTo(ZentraleStange_XValue, ZentraleStange_YValue+40, ZentraleStange_ZValue-(TiefeQuerbalken/2)-1);
59.   ellipsoid[1].moveTo(ZentraleStange_XValue, ZentraleStange_YValue+40, ZentraleStange_ZValue+(TiefeQuerbalken/2)-1);
60.   ellipsoid[2].moveTo(ZentraleStange_XValue-(TiefeQuerbalken/2)+0, ZentraleStange_YValue+40, ZentraleStange_ZValue);  
61.   ellipsoid[3].moveTo(ZentraleStange_XValue+(TiefeQuerbalken/2)+0, ZentraleStange_YValue+40, ZentraleStange_ZValue);
62. } // function
63. void draw() {
64.   background(153);
65.   textMode(SCREEN);
66.   fill(242);
67.   //text(actualTextMessage + " (now: " + actualTextMessage2 + ").", 10, 30);
68.   //CheckCamera();
69.   CheckCameraSinusLevel();
70.   //  Grass();
71.   stroke(22);
72.   PaintLamppost();
73.   Angle=Angle+1.0;
74.   if (boolGoesOnAPath) {
75.     PathValue=PathValue+1;
76.   }
77.   PaintHangingBasket();
78. }
79. // =====================================================================
80. void PaintHangingBasket () {
81.   // Schleife!
82.   for (int i = 0; i < ellipsoid.length; i = i+1) {
83.     stroke(22);
84.     // Blumenkasten
85.     ellipsoid[i].fill(color(72, 66, 44));
86.     ellipsoid[i].draw();
87.     stroke(22);
88.     // je zwei Drähte
89.     line (ellipsoid[i].x()-10, ellipsoid[i].y(), ellipsoid[i].z(),
90.     ellipsoid[i].x(), ellipsoid[i].y()-43, ellipsoid[i].z());
91.     line (ellipsoid[i].x()+10, ellipsoid[i].y(), ellipsoid[i].z(),
92.     ellipsoid[i].x(), ellipsoid[i].y()-43, ellipsoid[i].z());
93.     // je drei Blumen
94.     pushMatrix();
95.     translate (ellipsoid[i].x(), ellipsoid[i].y()-17, ellipsoid[i].z());
96.     scale(.2);
97.     rotateY(.7);
98.     //Flower(1, 1, +200, 17, 3);
99.     popMatrix();
100.     pushMatrix();
101.     translate (ellipsoid[i].x()-2, ellipsoid[i].y()-17, ellipsoid[i].z()-2);
102.     scale(.25);
103.     rotateY(2*PI-.2);  
104.     //Flower(1, 1, ellipsoid[i].x()-22, ellipsoid[i].y()+117, ellipsoid[i].z()-21);
105.     popMatrix();
106.     pushMatrix();
107.     translate (ellipsoid[i].x()+2.2, ellipsoid[i].y()-17, ellipsoid[i].z()-2.3);
108.     rotateY(1.32);  
109.     scale(.23);
110.     //Flower(1, 1, +2, 7, 221);
111.     popMatrix();
112.   } // for
113. } // SR
114. // =====================================================================
115. void PaintLamppost () {
116.   // http://en.wikipedia.org/wiki/Street_light
117.   // central lamppost
118.   pushMatrix();
119.   int Hoehe = 220;
120.   fill(190, 3, 3);
121.   translate(ZentraleStange_XValue-0,
122.   ZentraleStange_YValue+(Hoehe / 2),
123.   ZentraleStange_ZValue-0);
124.   rotateY(0.0);
125.   box(11, Hoehe, 11);
126.   popMatrix();
127.   // Querbalken 1
128.   pushMatrix();
129.   fill(9, 3, 233);
130.   translate(ZentraleStange_XValue,
131.   ZentraleStange_YValue,
132.   ZentraleStange_ZValue);
133.   rotateY(0.0);
134.   box(11, 11, TiefeQuerbalken);
135.   popMatrix();
136.   // Querbalken 2
137.   pushMatrix();
138.   fill(9, 9, 223);
139.   translate(ZentraleStange_XValue,
140.   ZentraleStange_YValue,
141.   ZentraleStange_ZValue-0);
142.   rotateY(radians(90.0));
143.   box(11, 11, TiefeQuerbalken);
144.   popMatrix();
145. }
146. void CheckCameraSinusLevel () {
147.   // Rotates in "Height"
148.   if (keyPressed) {
149.     // look to scene (center)
150.     camera (
151.     Radius*sin (radians(Angle)) + ZentraleStange_XValue, Height, Radius* cos (radians(Angle)) + ZentraleStange_ZValue,
152.     ZentraleStange_XValue, ZentraleStange_YValue, ZentraleStange_ZValue,
153.     0.0, 1.0, 0.0);
154.   }
155.   else {
156.     // look ahead 
157.     camera (
158.     Radius*sin (radians(Angle)) + ZentraleStange_XValue, Height, Radius* cos (radians(Angle)) + ZentraleStange_ZValue,
159.     Radius*sin (radians(Angle+5)) + ZentraleStange_XValue, Height, Radius* cos (radians(Angle+5)) + ZentraleStange_ZValue,
160.     0.0, 1.0, 0.0);
161.   }
162. }

for slow down, you can also turn to lerp()

feed arrCircleCenters[i] and arrCircleCenters[i+1] into lerp
and a float "amt"
then you can add a small amount to this last parameter of lerp

so you have a lot of points between arrCircleCenters[i] and arrCircleCenters[i+1] 
and can go very slowly

see

http://processing.org/reference/lerp_.html


https://forum.processing.org/topic/the-problem-with-car-objects#25080000001585603