Your first physics scene

Goal: drop a ball onto a platform, pause it and restart from the initial state. Allow 25–35 minutes.

See the result first

Drop a dynamic ball onto a fixed platform. Learn rigid bodies, colliders, gravity and the difference between running, pausing and restoring the initial scene.

Actual screenshots of the completed example. Click an image to enlarge it.

Before starting · ball above the platformThe initial ball center is at Y=3. The platform is fixed and simulation has not started.

After running · ball on the platformGravity pulls the ball down. After colliding with the platform it rests on the surface, with its center near Y=0.4.

The screenshots show the initial and final states. You can also pause the simulation and reopen the scene to repeat the drop.

Try it yourself

Starting archive · Completed archive

1. Check the geometry

Import the starting archive. Platform measures 6 × 0.3 × 5 at (0, -0.15, 0). Ball has radius 0.4 and starts at (0, 3, 0). The platform top is Y=0; the objects must not overlap initially.

2. Configure the physics world

Enable physics, set gravity to (0, -9.81, 0) and choose manual start. Keep the initial authoring positions until the simulation begins.

3. Configure both bodies

Object	Body	Collider	Parameters
Platform	Fixed	Box	Size 6, 0.3, 5
Ball	Dynamic	Ball	Radius 0.4, mass 1

Use friction 0.5 and restitution 0.2. Visible geometry and collision geometry are separate: a sphere mesh alone is not a physics collider.

4. Save and run

Open the runtime and press Start. Ball should fall and settle on Platform, with its center near Y=0.4; small numerical differences are normal. Pause should hold its position. Resume should not create another ball. Reload or reset the scene to return Ball to Y=3 before starting again.

• Ball falls while Platform remains fixed.
• Ball does not pass through Platform.
• Pausing stops movement.
• Three runs from the same initial state behave consistently.
• Body and collider settings survive saving and reopening.

Troubleshooting

No fall: check Start, enabled physics and Dynamic body type. Falling through: check collider dimensions, initial overlap and scaling. Falling platform: use Fixed. Different restart positions: distinguish resuming from resetting the initial scene.

This introductory exercise is not an engineering accuracy or equipment safety validation. Continue with physics simulation for joints, drives and motion paths.