File list

Introduction

On this page, we will take a look at how to create a basic animation, the process of getting it in-engine, and gain an understanding of the .model_animation_graph tag. The overall goal of the following tutorial is to add an animation to our platform scenery to make it move in-engine.

Animations in Blam!

Animation in the Blam! engine is quite a broad topic and not everything will be covered here, but the following basics should give you a good enough understanding such that you can create animations for any scenery or device machine object you wish. Unlike models, which all use the .JMS format for importing, animations use a multitude of formats that determine how tool handles them on import. You can see a list of all types here, but the main two we will focus on are .JMM and .JMO. Think of .JMM as the "base" type of animation - one that causes an object's bones to simply move. The most common use-case is for object idling animations. .JMO are overlay animations - these are additive meaning that the bone movement data is applied on top of any current base animation on the object. When talking about things that apply to all extension types, I will use .JMx to indicate any extension.

Some animations require specific numbers of frames, where certain actions happen on certain frames - this is not the case for basic scenery or device machine animations, but is something you should keep in mind in the future. For example, wheel-based vehicle (think Warthog) steering animations only consist of four frames: rest, full-right-turn, rest, full-left-turn.

Vertex weighting

Vertex weighting is a complex topic - it is the process of determining how the vertices in a 3D mesh are manipulated by the movement of bones in an armature. If you'd like to learn more, a good place to start is the official Blender documentation. Luckily, the weighting that we have to do for our model is extremely simple. As we only have one bone, and we want the entire model to follow the animation of that bone, we can simply weight all of the vertices in our model to that bone, with a value of 1.

1. Open your Blender file from the last tutorial, or download the end result from the previous page.
2. Select the platform object, then navigate to the Object Data (green) tab in the Properties window.
3. At the top, locate the Vertex Groups section, and click the + symbol. This adds a new vertex group to the model.
4. Vertex groups rely on their name to determine which bone they are tied to. Put simply, rename the vertex group to Bone to match the name of the bone in the armature.

   

5. In the 3D Viewport, press Tab to enter into Edit Mode. Set your selection mode to Vertex with the buttons to the right of the mode dropdown. You will notice that four new options have popped up underneath the Vertex Groups section - Assign, Remove, Select and Deselect. Assign takes any currently selected vertices, and assigns them to the currently selected vertex group. Remove does the opposite. Select will highlight any vertices assigned to the currently selected vertex group. Deselect does the opposite.
6. Press A in the 3D Viewport to select all vertices in the model (they will turn orange). Then, in the Properties window, hit the Assign button with the Bone vertex group selected.
7. In the Properties window, switch to the Modifiers (wrench icon) tab. We need to add an Armature modifier to our model, so that the newly added vertex group knows which armature to use (we only have one armature in the scene, but it needs the modifier regardless).
8. Click Add Modifier, then choose Armature at the top of the Deform column.
9. In the newly added Armature Modifier, click inside the Object field, and choose Armature. Ensure that Bind To Vertex Groups is checked.

That's it! Our platform object will now correctly animate with the armature, once we have created an animation. If you wish to perform a check to make sure you have done these steps correctly, do the following:

1. In the 3D Viewport window, click the mode select dropdown near the top left and choose Pose Mode. Pose mode is a special object mode used to create keyframes for animation, but we will use this more in the next section.
2. Expand the Armature in the Outliner window, and select the Bone.
3. Hover over the 3D Viewport, and press G to move the bone. As you move your mouse to move the bone around, the platform object should follow it. Don't worry that the physics object doesn't do the same - we will talk more about this later.
4. Right-click to stop moving the bone, or use Ctrl + Z to undo any changes if you accidentally made them. Then use the mode selection to return to Object Mode.

Creating an animation

Our second goal is to make a simple animation to play on our .scenery object - a spinning animation will do nicely, and is easy to create with only a few keyframes.

1. Ensure that you can see the Timeline window (at the bottom of the screen in the default workspace). It is recommended to expand it vertically slightly for better visibility, as per the image below.

   

2. In the Timeline window, set the End value to 80. This number is the end frame - we start at 1, and the animation now ends at 80. Animations are played at 30 frames per second in-engine, so this animation will last roughly 2.67 seconds.
3. Select the Armature object in your scene.
4. Use the Mode drop-down menu in the top right of the 3D View to switch to Pose Mode.
5. Select the bone in the armature (named Bone). You can do this by zooming in and left-clicking the bone in the 3D View, or by expanding the dropdown on the Armature object in the Outliner view on the right.
6. Make sure the currently active frame is 1. You can do this by dragging the blue slider in the Timeline window to the start, or by typing 1 into the box in the top right, next to the Start and End frame boxes.
7. Hover your cursor over the 3D Viewport window, and press I. This will open the keyframe window - choose Rotation.

8. Use the timeline slider or the frame number box to set the current frame to 20.
9. In the 3D Viewport, press R, then Z, then type 90. Left-click or press Enter to confirm. This rotates the bone by 90 degrees, or one-quarter turn, and the platform object follows suit.
10. Hit I to open the keyframing menu, and select Rotation to store the current rotational data into frame 20.
11. Move the timeline to frame 40. Once again press R, then Z, then type 90, followed by a left-click or the Enter key to apply. As before, use I to open the keyframe menu and keyframe the Rotation data.
12. Move the timeline to frame 60, and repeat the rest of Step 11.
13. Move the timeline to frame 80, then repeat Step 11 one final time.

On frame 80, the bone and platform should now be back in their original rotation. You've done it - this is all that is required to make an anti-clockwise spinning animation! Press the play button in the top middle of the Timeline window to see your animation play on loop. You can use the other controls to skip to the start or end frame, or step through the animation one frame at a time. It should look like this:

However, you may or may not have spotted an issue - the animation looks "jerky", as it slows down and speeds up slightly as it approaches each keyframe. We need to change blender's extrapolation mode to linear to make it nice and smooth:

1. Click the Editor Type drop-down in the top left of the Timeline window (the clock icon). Select Graph Editor.
2. Click the Channel heading, the Extrapolation Mode, then Linear Extrapolation.
3. Open the Editor Type drop-down again and set it back to Timeline. Play the animation again, and it will loop smoothly.
4. You can now leave Pose Mode and return to Object Mode in the 3D Viewport.

Exporting animations from Blender

As you should already be familiar with exporting .JMS files from Blender with the Blender addon, the export process for animations should feel at least somewhat familiar.

1. Click File -> Export and choose Halo Jointed Model Animation (JMA).
2. Navigate to your the custom_platform's data directory - that would be "H3EK\data\objects\scenery\custom_platform" if you have been following along exactly.
3. Create a new folder here (the Create New Directory button to the left of the file path box), and name it animations. As with the render and physics folders, tool.exe looks specifically for this folder name, so make sure it is named correctly.
4. Navigate inside the new animations folder.
5. On the right side of the export menu, make sure the Game Version is set to Halo 3, and the Extension is set to JMM. Leave everything else default.
6. At the bottom of the export menu, name the file any idle exactly.

7. Hit the Export Animation button, and wait for the Export completed successfully message to appear at the bottom of Blender.

Importing animations and the model animation graph

Animations are stored in .model_animation_graph tags once imported. This tag type is automatically generated on first import, similarly to how a .render_model tag is built automatically when you first import a .JMS. These tags can contain as many animations as needed, and are re-built whenever the animations folder is imported. This re-building process deletes any existing animations in the tag, and then adds those found in the animations folder back in. This means that if you no longer have the source .JMx files for some animations and attempt to import others, they will be removed.

Let's go through the process of importing our new any idle.JMM file:

1. Open up CMD in your H3EK folder. The command we will be using this time is model-animations.
2. Type tool model-animations "path\to\your\scenery", where path\to\your\scenery is the tags-relative path to your scenery's data folder. For example if you have been following along exactly, this will be "objects\scenery\custom_platform".

You should now see the following output from tool, informing us that the .model_animation_graph tag has been successfully created (it will be alongside the other tags, e.g. in "H3EK\tags\objects\scenery\custom_platform"). The warning and error here can be ignored - they are simply informing us that a new tag is being made from scratch:

The Skeleton Nodes block lists all of the bones used in this model and animation. In Blam!, bones are called nodes. We only have one node, and so there is only one entry in this block. The node list of a .model_animation_graph and the .render_model it is associated with must match exactly. You will get an error when importing animations if they do not. If you change something after the fact, such as editing the render model to add new bones but not updating the animation to reflect this, the node lists will no longer match, and the object will refuse to spawn at all.

The Animations block is quite obvious - it lists all of the animations held in the tag, and their associated data. Here you can see our named animation. Note that spaces are replaced with colons in Guerilla, such that any idle.JMM becomes any:idle in the tag. One use of this block is to add sounds that play on certain frames of the animation - this is done in the Sound Events sub-block.

The Mode-n-State Graph block shows in what states the animations in the graph will play. As we named the animation any idle, tool recognised that it is to be played under any circumstance, and so it is already set up correctly in this block. This is why naming conventions for .JMx files are important, as it tells tool how to automatically handle them. Our idle animation will therefore play for any mode, in any weapon class, and in any weapon type. You can see the reference to the any:idle animation here in the Actions section. Actions are base animations, such as .JMA and .JMM, whereas the Overlays section is for .JMO animation types.

Playing the animation in-engine

It's about time we saw that platform spinning in Sapien! We've already done 99% of the hard work, so let's do the final steps:

1. In Guerilla, open the .model tag for the platform.
2. Right at the top, locate the animation entry - it's in between the entries for the .render_model and .physics_model that we have already added.
3. Click the ... next to the animation entry, and open the new .model_animation_graph tag.
4. Save the tag.

   

5. Open Sapien on a map of your choice, and add the platform scenery tag to the scenery palette if you haven't added it already. If you can't remember how to do this, refer to this section of the render importing guide
6. Place the scenery down anywhere, and witness it spin!

   

Acknowledgements

Thanks to the following individuals for their research or contributions to this topic:

• PepperMan (Writing this guide)