Locomotion with height-based animation adjustments

Locomotion with height-based animation adjustments is an important concept in game development and character animation, particularly for characters or entities that need to move across varying terrains or interact with different environmental heights. The idea is to adjust the movement and animations of a character based on their height or the height of the terrain they are interacting with. This ensures the character’s movements look more natural, as well as making the gameplay experience more immersive and responsive.

Here’s an overview of how this works:

1. Understanding Locomotion

Locomotion refers to the movement of a character or object, which can include walking, running, jumping, crouching, and other forms of movement. In games and animation, locomotion is often achieved using animation cycles or blends that are triggered by different conditions like speed, terrain, and height.

2. Why Height Matters in Locomotion

When characters are on uneven ground, such as stairs, hills, or cliffs, their movement needs to reflect these changes in terrain. A flat animation for running or walking may not look convincing when the character is climbing a steep incline or descending from a ledge. Thus, adjusting locomotion based on height helps to create more realistic and responsive animations.

3. Types of Height-Based Adjustments

a. Terrain Height Changes

When a character moves across surfaces that vary in height, their posture and movement will change. For example:

• Climbing/Descending: When a character climbs a ladder or moves up a steep slope, the walking or running animation may need to transition into a climbing or crawling animation. Conversely, descending a slope may trigger an animation that simulates gravity and the downward force on the character.

• Uneven Terrain: If the character is walking across a rocky surface or uneven ground, their walking or running animation might need to adjust for different foot placement. For example, their step length or stride might be shortened, or the character might lean forward or backward to maintain balance.

b. Height-Based Crouching and Standing Animations

In many games, characters can crouch or stand based on specific actions or gameplay mechanics. For instance, when moving through narrow spaces, characters may automatically crouch, and their locomotion should adjust accordingly.

• Crouch Animation: When a character crouches, their running animation becomes slower, and their movement style changes to reflect their lower body stance.

• Standing Animation: If the character needs to move across a surface where they can stand up, the animation will transition from crouch to normal locomotion.

c. Jumping and Falling Animations

The height of a character’s jump or fall affects the animation’s behavior. For example:

• Jumping: A jump animation typically has a rise and fall, and the height of the jump may affect the speed of the animation.

• Falling: If the character falls from a great height, gravity-based animations like free-fall or impact animations will need to adjust based on the fall distance.

4. Implementing Height-Based Animations

a. Animation Blending

Most modern game engines, like Unity or Unreal Engine, use animation blending to combine multiple animation clips based on certain conditions. In the case of height-based locomotion, this could involve blending between different animations such as walking, running, climbing, or falling, depending on the height the character is at or the terrain they are on.

• Example: If a character is walking on flat ground, the engine might blend a standard walking animation. However, when the terrain increases in height (e.g., the character climbs), the system might blend into a climbing animation.

b. Raycasting for Terrain Detection

Raycasting is often used in games to detect the terrain under the character. This method casts an invisible line (ray) from the character’s feet to the ground and determines the height of the terrain. Based on this height difference, the animation system can adjust the character’s movement.

• Example: If a raycast detects that the character is walking uphill, the locomotion system can adjust the character’s forward lean, adjust the stride length, or blend into an uphill-running animation.

c. Inverse Kinematics (IK)

Inverse Kinematics can be used to adjust the positioning of a character’s legs and feet based on terrain height. For instance, when a character is walking up or down a slope, IK ensures that the feet will align properly with the ground, adjusting for any changes in terrain height. This can prevent issues like the character’s feet floating above the ground or sinking into it, making the animation more believable.

• Example: When walking on uneven terrain, the feet should adjust to the height changes of the ground, with one foot slightly elevated when stepping up a rock, while the other foot is lower.

5. Practical Examples of Height-Based Animation Adjustments

a. First-Person Shooter (FPS) Games

In FPS games, where the character’s height changes can dramatically impact movement speed and animation fluidity, adjustments are particularly important. Players may need to crouch, jump, or climb over obstacles. Height-based locomotion adjustments can make the transition between standing, crouching, and climbing smooth and realistic.

• Example: When a player jumps and lands on a high platform, the landing animation should reflect the height of the fall, such as a heavy impact for long drops.

b. Platformers

In platformer games, characters often move between different heights. Games like Super Mario or Celeste require precise height-based adjustments for jumping, landing, or climbing. In these types of games, height-based adjustments can include changes to the jump arc, speed, and animation blending for different fall distances.

• Example: In Super Mario, the character’s jump height adjusts based on how long the jump button is held down, and falling distances impact the landing animation.

c. Open-World Games

In open-world games, such as The Witcher 3 or Assassin’s Creed, characters interact with complex environments. Height-based animation adjustments are critical for these environments to create fluid movement across hills, buildings, and various terrain types.

• Example: If the player climbs a building, the character’s climbing animation will reflect the height and the difficulty of the climb, adjusting based on the surface the character is on (e.g., ledges, roofs, or walls).

6. Challenges in Height-Based Animations

While the concept is powerful, implementing height-based locomotion adjustments can be challenging:

• Smooth Transitions: It can be tricky to create smooth transitions between different locomotion states, especially when the height changes dramatically.

• Performance Concerns: Processing height-based terrain changes in real-time for every character can be computationally expensive, particularly in large open-world games.

• Complexity in Animation Blends: Creating an animation system that can handle complex transitions between different movements (e.g., walking to climbing or running downhill) requires careful animation blending and may involve multiple layers of animation states.

7. Conclusion

Incorporating height-based animation adjustments into a game’s locomotion system ensures that characters move in a more natural, responsive way to environmental changes. This approach involves using techniques like animation blending, raycasting, and inverse kinematics to detect and adjust for height variations. Although challenging, height-based locomotion is crucial for enhancing realism, improving player immersion, and ensuring that characters react dynamically to their surroundings.