Descriptions and Examples for the POV-Ray Raytracer by Friedrich A. Lohmüller
    3D Animations with POV-Ray
        Some basics and examples on animations.
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  3D Animation Tutorial
   Index of Content
  0. Basic Knowledge
     1. Basic Example
     2. Example 2
     3. Images to Animated Gif
     4. From Images to Video
     5. Basic Terms
     6. Animation Commands  
  I. Cyclic Animations
     1. Rotating Objects
     1.2. Planets in Orbit
     1.3. Clock Animation
     2. Rotating Camera
     2.1. Straight Moving Camera
     3. Western Wheel
     3.1. Rolling Wheels
     4. Gears
     4.1. Roller Chain
     4.2. Bike Chain
     5. Swinging Pendulum
     5.1. Newton's Cradle
     5.2. Rock the Rocker
     6. Spiral Pendulum
     7. Coupling Rods
  > 7.1. Connecting Rods
     8. Psychedelic + Op-Art
     9. Counters + Countdowns
    10. Folding of a Cube
  II. Non-linear Movements
     1.0 Speed Up/Slow Down 1
     1.1 Speed Up/Slow Down 2
     2. Fall + Bounce
     3. Acceleration by
          physical Formulas
     4. Speed Controll by
          Spline Functions
  III. Animation Paths
      with Spline Curves
     1. Spline Curves
     2. Closed Splines
     3. Animation Paths

Connecting Rods

Cyclic animation with sine and cosine function.

Connecting Rods:
By this motion the given values are the angle of rotation of the wheel "Wheel_angle", the radius of the point, where the connection rod is fixed at the wheel "C_radius" and the length of the connection rod "C_Rod_Len".
With this values we can calculate (see also the image below) the x and y values of the point where the connection rod is fixed at the wheel and the rotation angle of the connection rod
(Note: Sine and cosine in POV-Ray need the angle in radians: if the "Wheel_angle" is given in degrees we have to use "radians(Wheel_angle)"!).


scene description
for POV-Ray:
"con_rod1.ini" and
#declare C_x =  C_radius * cos(radians(Wheel_angle));
#declare C_y =  C_radius * sin(radians(Wheel_angle));
#declare C_Rod_y = C_y;
#declare C_Rod_x = sqrt(C_Rod_Len*C_Rod_Len-C_Rod_y*C_Rod_y);
#declare C_Rod_Angle = degrees(atan2(C_Rod_y,C_Rod_x));

Attention : For guarantee of the mechanically correct flow of this motion, it is necessary that the piston rod is in the same line as the axis of the wheel. So it's a good idea, to construct the complete combination with the wheel centred at <0,0,0> and then to move altogether upwards by the radius of the wheel.
Some examples for animations of this kind
you can find here: 3D-Animations - Railroad (steam engines)
and here: 3D-Animations - Engineering (4- u. 6-cylinder engines).


© Friedrich A. Lohmüller, 2010