How to Make a Cube Move in Unity 3D?

Moving a cube in Unity 3D can be achieved in various ways, from simple translation to complex physics-based movements like rolling. A common and visually engaging method, especially when simulating dice or block movements, involves rolling the cube by rotating it around one of its edges or corners.

Moving a Cube in Unity 3D: The Rolling Method

One dynamic way to make a cube move in Unity 3D is by simulating a rolling action. Instead of simply changing its position directly, you rotate the cube around a pivot point located on one of its edges or corners. This creates the effect of the cube tumbling over.

Key Concepts for Rolling

Implementing cube rolling effectively requires understanding a few core ideas:

• Center of Rotation: This is the crucial point around which the cube rotates during a roll. It's typically an edge or corner that touches the ground or the surface it's rolling on. As the reference indicates, you need a variable to store this point. "So we go back to our code to change a few things. We add a new variable to store the center of rotation."
• Determining the Center: The specific location of the center of rotation depends on the direction the cube is rolling. If you're moving right, the center will be the bottom-right edge (or corner) of the cube relative to its current orientation. The reference highlights this: "When moving right it should be here. So it's the cube's." This means the center's position is calculated based on the cube's own transform and size.
• Applying Rotation: Once the center of rotation is determined, you apply a rotation to the cube's transform, using the calculated center as the pivot point. A full roll is typically a 90-degree rotation.
• Controlling the Roll: To make the movement smooth, you don't apply the full 90-degree rotation instantly. Instead, you apply it gradually over time, often using techniques like Quaternion.Lerp or Vector3.RotateTowards.

Implementing Cube Rolling

Here are the general steps to implement cube rolling using a script in Unity:

1. Create a C# Script: Attach a script (e.g., CubeRoller.cs) to your cube GameObject.
2. Define Variables:
   • Variables for movement input (e.g., horizontal/vertical axis).
   • A variable to store the target rotation.
   • A variable to store the center of rotation for the current roll (as mentioned in the reference).
   • Variables for controlling rotation speed or duration.
   • A boolean flag to check if the cube is currently rolling.
3. Handle Input: In the Update method, detect player input (e.g., pressing arrow keys).
4. Start a Roll: If input is detected and the cube is not already rolling, calculate the following:
   • The target rotation: This is usually the current rotation plus a 90-degree rotation around the appropriate axis (X or Z) in the direction of movement.
   • The center of rotation: This is the critical step based on the input direction. Calculate the position of the edge or corner the cube will rotate around. This involves using the cube's current position, its scale (size), and the direction of movement. This is where "So it's the cube's" comes into play – you calculate this point relative to the cube's own transform.
5. Animate the Roll: In the Update or FixedUpdate method (if using physics), if the cube is rolling:
   • Gradually rotate the cube from its current rotation towards the target rotation, using the calculated center of rotation as the pivot. Methods like transform.RotateAround() or manual quaternion interpolation can be used.
   • Ensure the rotation speed or duration is controlled for smooth animation.
6. End the Roll: Once the cube reaches the target rotation (or is very close), snap its rotation to the exact target angle (e.g., multiples of 90 degrees) and reset the rolling flag.

Scripting Details

Your script will need to track the current state and manage the rotation process.

Variable Name	Type	Description	Purpose
rotationCenter	Vector3	Stores the world position of the pivot for the roll.	Required as per reference. Used by RotateAround.
targetRotation	Quaternion	The final rotation the cube should reach.	Controls the end state of the roll.
rollSpeed	float	How fast the cube rotates (degrees per second).	Controls the animation speed.
isRolling	bool	Flag indicating if a roll is in progress.	Prevents starting a new roll mid-animation.
rollDirection	Vector3	The direction of the current roll (e.g., Vector3.right).	Used to calculate the rotationCenter.

Calculating the rotationCenter involves taking the cube's current position, finding the appropriate corner/edge vector relative to its local axes (based on rollDirection), scaling it by half the cube's size, and offsetting it appropriately, often by adding the cube's current position and potentially an offset for height if not rolling on a flat plane at Y=0.

Practical Tips

• Snapping: After a roll completes, snap the cube's rotation to the nearest 90-degree angle to prevent slight misalignments over time.
• Ground Check: Ensure the cube is on the ground before allowing a roll to start, especially if using physics.
• Animation Curves: For more advanced control over the rolling speed profile (e.g., easing in and out), consider using Animation Curves.
• Handling Consecutive Rolls: Design your script to allow the next roll command to be queued or initiated only after the current roll finishes.

By implementing this rolling mechanic, you create a visually appealing movement that is specific to the cube's shape and simulates physical tumbling.