Making Movies and Working with STK Models

STK Free , STK Pro, STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this training contacting AGI Support at support@agi.com or 1-800-924-7244.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

Capabilities Covered

This lesson covers the following STK Capabilities:

  • STK Pro

What you will learn

STK provides the capability to either save a collection of still frames from the 2D or 3D window, and compile them into a movie with third party software, or save a ready-to-play movie directly from STK. Movie making can be divided into three parts:

  1. Preparing the Scene
  2. Controlling the Camera
  3. Rendering Content

This tutorial covers preparation, camera control, and rendering content. In an ideal world you would prepare your scene before positioning the camera, but sometimes you don’t realize something needs to be added, removed, or changed until after the camera has been positioned. So, in a real situation, you may find yourself switching back and forth between the first two steps.

A movie, for the purpose of this discussion, is a single scene of continuous motion. A movie may run from a few seconds to a few minutes, depending on your requirements. Movies tell a story. The story can be about something that has happened, might happen, or something that is happening right now. Scenarios in STK do the same thing, but often cover a much larger area in both time and space than a single movie can convey. This tutorial assumes that your scenario is technically complete. Preparing the scene, which comes next, is what you do to make it movie ready.

Video guidance

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Open a previously created scenario

We will open a previously created scenario and then begin to prepare the scene.

  1. Launch STK ().
  2. Click the Open a Scenario () button.
  3. Browse to <STK Install Folder>\Data\Resources\stktraining\VDFs.

    4. If using an older version of STK, browse to <STK install folder>\Data\ExampleScenarios and open Intro_STK_Space_Systems.vdf.

  4. Select Models_And_Movies.vdf.
  5. Click Open.

Save the starter scenario as an *.sc file

When you open the scenario, STK creates a folder with the same name as the scenario in the default user folder. STK does not automatically save the scenario. When you save a scenario in STK, it saves in the format in which it orginated. Therefore, if you open a VDF, the default save format is a VDF. The same is true for a scenario file (*.sc). To save the VDF as a *.sc file, change the file format using the Save As procedure below.

  1. Select the Save As option.
  2. Select STK User on the left side of the Save As window.
  3. Select Models_And_Movies and click Open.
  4. Change Save as type: to Scenario Files (*.sc) and click Save.
  5. Click Yes to confirm.

Save often!

The mission in this example is a Low Earth Orbiting (LEO) satellite that collects imagery of ground targets. It then downlinks the data to multiple ground stations while maximizing power to the satellite’s solar panels. The satellite’s orbit line is colored based on the intervals for payload imaging, antenna downlink, sunlight, penumbra, and umbra.

We will be making updates in the main 3D Graphics window.

Change the units

Optimizing visualization for movie making sometimes requires that you perform some simple calculations to determine your optimal bit rate and time step. Model articulations also reference times, such as their start, stop and duration, in epoch seconds. That being the case, it’s always good practice to change the date format to epoch seconds when using a scenario for movie making.

  1. Open Models_and_Movies's () properties ().
  2. Select the Basic - Units page.
  3. Change the DateFormat units to Epoch Seconds (EpSec).
  4. Click OK.
  5. In the Animation toolbar, click to Reset the scenario.

Preparing the scene

Engineers, as a rule, focus on technical accuracy more than aesthetics. If your audience is largely non-technical, aesthetics may be a powerful influence. The one question that you never want to hear is, "What was that?" Asking, "What was that?" means that the movie has failed to tell the intended story. There are three areas that comprise scene preparation:

  1. Lighting
  2. Framing
  3. Visual Elements

Lighting

Lighting parameters are on the 3D Graphics - Lighting page. For a complete description of the lighting panel, look here. STK's default lighting source is the Sun. To ensure good contrast, we will update the sun lighting.

Sun lighting

There are two settings for Sun Lighting: Global and Object. Global Lighting only affects how the sun lights the central body. Object Lighting only affects objects that are part of your scenario. This includes clouds and sensors.

The Ambient Level determines how bright the darkest parts of your globe or objects will be lit. To increase contrast, lower Ambient Level while increasing the Sun Level. Maximizing Global Sun and Night Lights levels (set them to 500) optimizes the sharpness of the solar terminator.

Under Object, the Ambient Level plus Sun Level should always equal 100. If it does not, objects in your scenario will appear either overexposed or underexposed.

  1. Click on Main 3D Graphics Window in the Integrated Workspace to bring it to the front.
  2. Right-click on the 3D Graphics Window and select Properties ().
  3. Select the Lighting page and make the following changes:
    1. Sun Lighting - Global
      OptionValue
      Ambient Level20.0
      Sun Level500.0
      Night Lights Level500.0
    2. Sun Lighting - Object
      OptionValue
      Ambient Level20.0
      Sun Level80.0
  4. Click Apply.

Flashlight

What if your movie starts out on the dark side of the Earth? Try not to let this happen. If your movie must start on the dark side, you can add additional lighting sources. A less precise, but much faster, solution is to use the flashlight.

  1. Return to the 3D Graphics windows properties - Lighting page.
  2. On the Flashlight panel, select the Show check box. Make sure the Level is set to 50.

Framing

Framing has to do with the shape and size of your video and the volume of space it contains. You can divide framing into two parts:

  1. Screen size
  2. Field of view

Screen size

Screen size is on the 3D Graphics - Window Properties page. You can choose one of the predefined window sizes from the drop-down, or you can define a custom window size. For desktop presentations, we recommend using 1280 x 720.

  1. Return to the 3D Graphics Windows properties.
  2. Select the Windows Properties page.
  3. Select 1280 x 720 (HDTV) in the Size drop-down list.
  4. Click Apply. The 3D Graphics window re-sizes.

Field of view

Field of view defines how much you can see, in degrees, in the 3D Graphics window. As your field of view gets wider, the objects in your 3D window get smaller, but you will also see more of them. The maximum angle is 160 degrees.

STK's default value for field of view is 45 degrees. A square 3D Graphics window has the same field of view in both directions. If the 3D Graphics window is 1280 pixels wide and 720 pixels high, only the largest dimension, in this case 1280, matches the field of view setting. Seventy (70) degrees is a good starting point for movie making.

  1. Return to the 3D Graphics Windows properties and select the Advanced page.
  2. Update Field of View to 70 deg.
  3. Click OK.
  4. Save () your work.

Visual elements

Visual elements of a movie include models, textures, and terrain. Some elements may move and change, others won't. Visual elements may have little to do with the technical nature of your scenario, but often add credibility to the technical parts that are already there. Depending on their size and frequency of use, some of these may impact performance.

Manage terrain, imagery, and globes

We are going to be recording our video zoomed in to the satellite, while it is in the sunlight. If you need to make globe enhancements or add terrain, you can do that in the Globe Manager. To enhance your 3D Graphics window, you can add a high-resolution Nightlights texture, animated water surfaces, a global specular highlight, and world cloud textures. Some of these visual elements are included in the STK install and the rest are on the supplementary data disk.

Remove objects

To clean up the scenario, if there are objects in your scenario that you do not need for the movie, you can either delete them from the scenario or toggle them off in the Object Browser.

  1. Disable SunSensor in the Object Browser by clearing the check box to the left of it.
  2. Disable SunSensorTrue in the Object Browser by clearing the check box to the left of it.

Enhance labels and annotations

Here are a few suggestions to improve the appearance of labels, annotations, and lines:

  • Remove any unnecessary labels and lines in your 3D Graphics Window. Go into the object's Properties () and to the 2D Graphics - Attributes page. Select the Basic radio button. Under Inheritable Settings, clear the Inherit from Scenario check box. Then you can clear any or all of check boxes such as label, orbit line, ground track, etc.
  • Remove any unnecessary annotations in your 3D Graphics Window. To disable annotations, go to the 3D Graphics Windows Properties () and select the Annotation page. There you can clear any check boxes for annotations related to time, viewer position, reference frame, etc.
  • Set your scenario so that LEO-to-target access lines do not appear in the movie. Right-click on the Models_and_Movies scenario, open Properties (), and select 2D Graphics - Global Attributes. Under Access, clear the Show Animate Line check box.
  • Labels and annotations look best in plain thick font. Thin or small font is difficult to read in a video. You can adjust the fonts under the Scenario Properties in the 3D Graphics - Fonts page.

Remove the Sun and VVLH vectors from LEO

  1. Return to LEO's () properties ().
  2. Select the 3D Graphics - Vector page.
  3. On the Vectors tab, disable the Sun Vector by clearing its Show check box.
  4. Click on the Axes tab and clear the VVLH and Body Axes check boxes.
  5. Click on the Body Axes line. Notice that Persistence is enabled, which will be a nice enhancement to the movie.
  6. Click Apply.
  7. Save () your work.

Models

You can use 3D models to represent scenario objects and aid in analyzing and visualizing the relationships among the objects. STK contains detailed 3D models representing objects such as ground stations, aircraft, air strips, satellites, aircraft carriers, and helicopters. Once you specify a model to represent an object, it is graphically displayed in its position and orientation as defined in the object's Basic properties. STK places the center of a model at the X, Y, and Z position of the object it is representing. Position and orientation can vary over time, and you can manually adjust them within the object's 3D Graphics properties. Supported model file types are:

  • MDL models (.mdl)
  • COLLADA models (.dae)

MDL Models

A model is a graphical representation of an object. You define that graphical representation in a model file, which is an ASCII text file with an .mdl extension (for example, sample.mdl).

A model file contains the following:

  • Description - This provides a detailed description of the model.
  • Components - Each component describes a specific part of the model, such as an antenna dish.
  • Primitives - A component contains one or more primitives that define the shape of the component.
  • Parameters - Parameters further describe a primitive or component.

Model files are arranged in a hierarchy of components and primitives. In the hierarchy, the component is the parent of all primitives and subcomponents contained within. A primitive that refers to a component is the parent of that component.

COLLADA Models

STK natively reads COLLADA (.dae) files. COLLADA is a popular, open, standards-based format that you can export from many 3D editing applications (such as 3D Studio Max, Maya, Softimage, Blender, and Google SketchUp) and from model converters such as:

  • Core, by Anark, recommended for CAD conversion
  • Deep Exploration, by Right Hemisphere
  • PolyTrans, by Okino Computer Graphics

Modify or create models

You may need to modify or create a model file if you:

  • Work in a classified environment
  • Need to add an attach point or an articulation
  • Require a new design

Once you have a model in COLLADA or MDL, you can add functionality. Ancillary features consist of articulations (moveable components), attach points, pointable elements, and solar panel groups.

Model articulations

A model articulation defines a range of positions and orientations for a component or primitive, such as the allowable gimbal angles for an antenna.

Articulations do not change the way an STK object is defined, and they do not affect access or other calculations between objects being modeled. Use it to visually resolve anomalies or to provide realistic motion in the models for animation.

You can edit articulations in a few ways:

  • In the Object's Properties, on the 3D Graphics - Model page
  • Manually, in the Movie Timeline Tool
  • In the articulations file

This scenario is using an articulation file that is automating the execution of moving parts at the appropriate time. It contains the information needed to animate the articulation commands contained in the model file. The model articulation file contains a time-ordered list of data about each articulation that can be applied to the associated object.

Look at LEO's model properties

  1. Return to LEO's () properties ().
  2. Select the 3D Graphics - Model page.
  3. In the Model field, notice it is using voyeur_4.mdl.
  4. In the Articulations section,
    1. Click View to see the available articulations for this model.
    2. Close the Model Articulations window.
    3. Make sure that the Articulation File is enabled, and the file is LEO.sama. We will see when we create our movie that this file is telling the model when to open the Imaging Barrel Door and when to close it.
  5. Click Cancel.

Explore the articulation file

  1. Open Notepad++ or WordPad.
  2. Click on File > Open in the file type drop-down menu and select All Documents (*.*) if using WordPad. Leave it as All Types (*.*) if using Notepad + +.
  3. Navigate to the scenario folder (e.g., C:\Users\{User Directory}\Documents\STK 12\Models_and_Movies) and open the articulation file LEO.sama.
  4. Note the last two articulation in the file. This file defines when to articulate (in this case, open and close) Imaging_Barrel_Door and the duration of the articulations. When we make our movie, we will see that the door is opening before the first image collection and remains open during the image collection.

View the articulation in STK

  1. Return to STK.
  2. Play () the scenario, watch the Image Barrel Door open, and then watch it close in the 3D Graphics window. Increase Time Step () if you want to speed up the animation.

Make a movie

Camera control tool

Use the Camera Control tool () to define the path that the virtual camera takes during a technical animation. The Camera Control tool provides:

  • Keyframes property page - Use this page to add, modify, copy, and delete camera paths. Many of the functions on this screen are duplicated on the Camera Control toolbar.
  • 3D Window Properties page - Use this page to define camera control properties of a particular 3D graphics window.
  • Render Properties page - Use this page to control how the camera paths are drawn in the 3D graphics window.
  • Camera Control toolbar - Use this toolbar to interact with camera paths.

Open the camera control tool

  1. Return to STK.
  2. Click View on the Menu bar, select Toolbars, and then click 3D Camera Control.
  3. Click the Camera Control tool () icon to open the tool.

Create a camera path

To create a camera path, STK stores a series of keyframes at intervals along the desired path. The Camera Control tool will use these keyframes to build a smooth line using a splining algorithm. When you create a viewpath, you place these keyframes so that the desired regions of interest are in the camera’s view at the appropriate times.

There are many ways to go about making a great camera path, but nearly all of them share certain characteristics:

  • Avoid crowds: Make sure each keyframe evenly fills the 3D window as much as possible. Avoid bunching relevant action into one area and leaving wasted space elsewhere. This happens a lot to object labels. Remove any non-essential labels. Labels must always be legible.
  • Stay focused: Keep relevant action near the center of the frame as much as possible. If the relevant action goes out of frame between keyframes, pause your scenario and add a new keyframe where this happens. If you want to change a keyframe, double-click the keyframe, reposition the camera, and overwrite the keyframe with your new camera position by clicking ADD. The viewer position, direction, and time will change to that of the selected keyframe. In each scene that you record, there should be a single “money shot” that depicts the essence of what you wish to convey.
  • Keep moving: Once the camera is moving in a given direction, keep it moving in that direction. If you run out of room, start sooner, but never reverse direction. Home movies are famous for this. The camera looks like it’s attached to a windshield wiper. This conveys confusion and a lack of confidence to the viewer. If you must move in the opposite direction, start by moving diagonally, then at a right angle, opposite diagonal, and finally opposite. Move like an ice skater.
  • Mind the gap: Keep keyframes evenly spaced. When there is a profound change in camera location or direction, users experience unpredictable camera motion between keyframes. If you are lucky, this may work for you.
  • Less is more: The fewer keyframes you have, the smoother your camera path will be. Each keyframe produces a change in the spline. If you have too many keyframes, your path will appear bumpy. Delete keyframes that don't contribute. Add keyframes between other keyframes to stay focused.

Set the start and stop times of you scenario to the desired movie start and stop times.

  1. Open the Models_and_Movies's Properties ().
  2. On the Basic - Time page, in the Animation field, click the down arrow next to Start Time.
  3. Extend the Start Time menu and select Replace With Time.
  4. Enter the start time of your movie as 5.0 EpSec, when the Imaging Barrel Door begins to open.
  5. Select the check box to the left of Stop at Time. Then click the down arrow , click Stop Time, and select Replace with Time.
  6. Enter the stop time of your movie as 315.0 EpSec, just after the Imaging Barrel Door finishes closing.
  7. Click Apply.
  8. Change the Step Size to 0.2 sec, and click OK.
  9. Click Reset () on the animation toolbar. The scenario resets to the time you want the movie to begin.

The safest way to produce a camera path is to establish starting and ending keyframes.

The beginning of your movie often familiarizes viewers with the context of your scenario. It is called an establishing shot. For this keyframe, you almost always want to position the camera some distance away. It is good to have balance in the keyframe. For example, have action on the left and action on the right. Try to make the key frames at points where you really want the camera to show the very best visuals that you can arrange. It is good to try to capture some dramatic lighting or show a feature of Earth.

Create the first and last keyframes

  1. Bring the 3D Graphics window to the front.
  2. Zoom to LEO and reposition the view in the 3D Graphics Window so there is balance on the screen. For example, LEO is zoomed in on the left and the target is in view on the right while still seeing the horizon.

  3. Return to the Camera Control tool and select the Keyframes page.
  4. Click New. This will add a new camera path segment to the table.
  5. Rename the camera path LEO_Image.
  6. Scroll down to the Keyframes area.
  7. Click Add. This will use the current scenario time to create the first keyframe.
  8. Create the last keyframe. Change the animation time to the end of the movie (315.0 EpSec).
  9. Bring the 3D Graphics window to the front.
  10. Use the mouse to manipulate the view to balance the action in the 3D Graphics Window. You can recenter your object if needed, then make the adjustments. Make sure you capture the action you want to see, such as LEO flying away from the Target on the ground.

  11. Return to the Camera Control tool.
  12. Click Add in the Keyframes area. This will add a second keyframe to your camera path.
  13. Click Apply.

Animate the scenario by following the camera path

  1. Double-click on Keyframe 1 to return to the beginning of the Camera Path.
  2. Select the 3D Graphics window to make it active.
  3. From the toolbar, click the Follow Path While Animating () drop-down list and select LEO_Image. You should now see a box around the Follow Path While Animating () button.
  4. Animate () the scenario to view the camera path. The path is from two keyframes; therefore it is a straight line rather than a spline. You need a third point to create the spline.
  5. Ensure the path in Camera Path is on (the Show check box is selected). Set the animation time to the halfway point of the movie (about 157.0 EpSec).
  6. It is likely the camera will be pointing the wrong way or looking at the wrong thing. Move the camera to where you want it to be at this time.
  7. Return to the Camera Control tool and click Add in the Keyframes area.
  8. Click Apply.
  9. Double-click on Keyframe 1 to return to the beginning of the camera path.
  10. Return to the 3D Graphics window.
  11. Ensure the Follow Path While Animating () button is enabled on the 3D Camera Control Toolbar.
  12. Click OK to close the Camera Control tool. Then start () the animation.

You can keep going to a time between keyframes to make your camera follows the path you want, but know that the fewer keyframes you have, the smoother your path will be.

Try to maintain a consistent amount of time and a consistent amount of change between keyframes. Change, in this case, relates to camera position and direction.

Render content

Rendering is the final step in making a movie.

  1. Reset () the scenario.
  2. In the 3D Camera Control toolbar, ensure the Follow Path While Animating () option is active.
  3. Right-click on the 3D Graphics window and open Properties ().
  4. Select the Record Movie page. By default, the Off radio button is active. Recording is disabled.

    5. Even if you save the scenario with one of the Record buttons active, the scenario will always be saved with the Off button active.

  5. Select the Record every Animation Time Step radio button. If you get an invalid path message, click OK.
  6. Choose the Directory where you want to save the movie, usually in the scenario folder location.
  7. Click Apply. With this option set, every frame that appears in the 3D Graphics window is saved to the computer's hard drive. This continues until you select the Off button and click Apply.
  8. SelectAnti-Aliasing option 3x3 from the drop-down.
  9. Click Apply and then OK.

Record the movie

  1. Bring the 3D Graphics window to the front.
  2. Click Start () on the animation toolbar. STK will begin writing either still frames or compile a movie file to your hard drive. It does not control the camera.
  3. The scenario will stop when the desired movie end time is reached, since that was set in the Scenario Properties. STK records the 3D Graphics window even If no camera path is activated. Recording continues until you reach the Stop Time of your scenario or you press pause ().
  4. Return to the 3D Graphics Window Properties - Record Movie page. Select the Off radio button and click OK. This is the only way to stop recording.
  5. Navigate to the directory where you saved the movie and play the movie.

Reset analysis time period

  1. Open Models_and_Movies's () properties ().
  2. In the Animation field, set the following:
    3. Option Value
    Use Analysis Start Time On
    Use Analysis Stop Time On
  3. Click OK.

Save your work

  1. When you are finished, reset () the scenario.
  2. Save () your work.