Download the files needed from the Requirements section and place then in your models folder of LDraw.

Open 6685_rotorblade.ldr using MLCad. You should see something similar to figure 2.

Figure 2: Viewing 6685_rotorblade.ldr in MLCad

The file is made up of three parts: Propeller 4 blade (Part # 3461), 1x8 Plate (Part # 3460), and Technic Axle 2 (Part #3704). We want the rotor blade to rotate around the center hole of #3461 propeller 4 blade, so we need to place that hole at coordinates 0,0,0.

Click on #3704 technic axle 2 place it at 0,0,0. One way of doing this is to right-click on your mouse (while the part is active) and choose the "Enter Pos. + Rot..." command, which will display a pop-up window shown in figure 3.

Figure 3: Changing coordinates of a part in MLCad

Replace the values in the X, Y, Z boxes with 0s.

Now click on #3461 propeller blade 4 and move it so that the middle hole is directly above the #3704 technic axle 2.

Move, copy and rotate #3460 1x8 plate to make the four rotor blade. In the end you should end up with the model shown in figure 4.

Figure 4: Rotor blade with Technic Axle 2

Open MLCad and click on the models category on the left hand side to see all the sub models of the helicopter and begin to drop and drag the sub-models to build the final model as shown in figure 5.

Figure 5: 6685 Fire Helicopter

Note: You must close and reopen MLCad to allow it the ability to refresh the models folder. Otherwise our newly created file (6685_mainrotor.ldr) would not have appeared.

Hint: When you place the 6685_mainrotor.ldr submodel on the body of the helicopter use toolbar menu items to see how it will rotate in the animation. Similarly use to see the rotation of the tail rotor. If they rotate "funny" then the point of rotation in each sub model file is wrong. Now would be the time to fix it!

Open the newly created POV-Ray file (we called it 6685_firehelicopter.pov) and render by clicking on the run menu icon. You should get an image similar to figure 7.

Figure 7: 6685 Fire Helicopter rendered in POV-Ray (default L3P/L3PAO settings) 

Scroll to the bottom of the file and we see (from bottom up) we see code for lights, camera, background, and floor. Next we see a line that looks like this:

object { _6685_firehelicopter_dot_ldr #if (version >= 3.1) material #else texture #end { Color7 } }

Hint: The code above appears on line 8902. At the very bottom of the POV-Ray window there is a window with a "L:". This informs you what line of code the cursor is at.

So what does line 8902 tell us? Well that is the final line of code that POV-Ray uses to render the entire model. All the lines above it are used to create individual parts for the model. So it takes eight thousand, nine hundred and two lines of code to make our 6685 Fire Helicopter!

Now look at the lines of code starting at 8893 that look like this:

object { _6685_body_dot_ldr matrix <0,0,1,0,1,0,-1,0,0,0,0,0> ...
object { _6685_canopy_dot_ldr matrix <0,0,1,0,1,0,-1,0,0,0,-108,-55> ...
object { _6685_pilot_dot_ldr matrix <1,0,0,0,1,0,0,0,1,0,-60,-30> ...
object { _6685_rotortail_dot_ldr matrix <0,0,-1,1,0,0,0,-1,0,45,-124,220> ...
object { _6685_mainrotor_dot_ldr matrix <1,0,0,0,1,0,0,0,1,2,-144,10> ...

Note: The lines of code had been truncated to only show the object name and matrix.

As you might have guessed each of these lines of code defines the sub-models we put together in MLCad. We only need to focus on the matrix coordinates for our animation. The code after the matrix is not important as it deals with the color of the sub-model. The matrix can be very intimidating but its easy to modify once we know what it tells us.

Let us concentrate on the main rotor object matrix.

• The first 9 numbers orient the part (NEVER EVER CHANGE THESE)
• The last 3 numbers tells POV-Ray where to place the object (MLCad's X,Y,Z coordinates in our case)

In our case we place the mainrotor.ldr at location 2, -144, 10 which is exactly what POV-Ray has! Don't believe us? Open MLCad and look at the "position values" for the mainrotor.ldr sub-model in the 6685_firehelicopter.ldr model.

When POV-Ray rotates something it will rotate the object around the 0,0,0 coordinate. For this reason we had to draw our main rotor around the 0,0,0 axis. Since POV-Ray can only rotate an object around the 0,0,0 axis we need to have POV-Ray move the object back to it's original location after the rotation. Have we lost you yet?

Okay lets change the code for the mainrotor object from this:

object { _6685_mainrotor_dot_ldr matrix <1,0,0,0,1,0,0,0,1,2,-144,10> ... 

to this

object { _6685_mainrotor_dot_ldr matrix <1,0,0,0,1,0,0,0,1,0,0,0> translate <2,-144,10> ...

Note: POV-Ray is case sensitive so make sure your code looks EXACLTY like the code above.

Render the file and you will get the same image as in figure 7.

Now add "rotate <45,0,0>" before the translate code we just added to make it look like this:

object { ... matrix <1,0,0,0,1,0,0,0,1,0,0,0> rotate <45,0,0> translate <2,-144,10> ...

and re-render the file. You should get an image like figure 8.

Figure 8: Rendering using Rotate <45,0,0> in object main rotor. 

The results are not exactly what we want for the animation but its all about trail and error. Try using rotate <0,45,0> and rotate <0,045> to see what type of results you get. One of them will rotate the main rotor alone the axis we want for the animation.

Hint: rotate <0,45,0> is the correct line of code for our animation. The keyword rotate and all other keywords in POV-Ray use the coordinates of <x,y,z>. Remember when you build the helicopter from all the sub-models and we told you to use the to rotate it? You were rotating the main rotors around the y-axis thus <0,45,0>.

Repeat the same line of thinking for the tail motor. In the end you should end up with a line of code like this:

object { ... matrix <0,0,-1,1,0,0,0,-1,0,0,0,0> rotate <clock * 4,0,0> translate <45, -124, 220> ...

Note: In real life the tail rotor of a helicopter spins faster than the main. To show this we will make the tail spin 4 times faster and that is done by multiplying the clock by 4.

Save your modified POV-Ray file as FH_Ani.pov and open up ani.ini. It will look this this:

; Animation INI File

Initial_Frame=1
Final_Frame= 30

;Subset_Start_Frame = 1
;Subset_End_Frame = 30

Initial_Clock=0
Final_Clock=360

Width=640
Height=480

Cyclic_Animation=on
Pause_when_Done=off
Output_File_Type=N 
; T - Uncompressed Tar 24-bit File
; N - New PNG (portable network graphics) format
; S - System-specific such as Mac Pict or Windows BMP
; C - Compressed Targa-24 format (RLE, run length encoded)
; P - Unix PPM format
Antialias=On
Antialias_Threshold=0.3 

Of interest to us are the number of frames (16 in this case) and the clock values (0 to 360). You can use any number of frames but anything under 15 and the human eye will notice that the animation is choppy and a series of images instead of smooth motion. Our choice of 30 is to follow the NTSC Video standards (i.e. US television, VCRs). Since we want to blades to rotate completely in a full circle they need to travel 360 degrees, thus the final clock value of 360 is used. Cyclic animation changes the clock value so when we repeat the animation there is no jump.

Click on the POV-Ray ini Menu icon to open the popup window in figure 9.

Figure 9: POV-Ray INI Window Settings

Use the browse button to locate the ani.ini file and click "Set but don't Render" button to close the window. Instead of using the default ini file (QUICKERS.INI) we will be using our own custom ini file for the animation as the default file does not have the clock value we need for the animation.

Click on the FH_Ani.pov file to see the code again and click on the icon. Sit back and enjoy as POV-Ray creates 30 images for your animation. Each image will show the helicopter blades moving just a bit.

Hint: To speed up the process of rendering ensure you are not running any other applications and use a quality level = 2 in your FH_Ani.pov file (line 11).

Hint 2: Reducing frames.
Since there are four main rotor blades the the frames will repeat after they turn 90 degrees.
In the INI file change final frame to 4 and final clock to 90. We get the same results in only 4 frames.