physics_bounce

English | 日本語

Overview

• This sample lets you inspect multiple spheres bouncing inside PhysicsSpace against the floor, walls, and one another
• It uses WebgApp to collect startup, HUD, input, and camera control while keeping the physics structure readable as a combination of PhysicsNode and Collider
• The spheres are drawn as instance shapes that use a shared ShapeResource, making it easy to confirm the structure "physics bodies are individual, render meshes are shared" even when increasing the count up to ?count=1000
• The floor uses PlaneCollider, the walls use BoxCollider, and the spheres use SphereCollider, so the differences between plane-sphere, sphere-sphere, and sphere-box bounce can be compared inside the same arena
• Pressing Space injects additional spheres during runtime, making it possible to inspect not only single drops but also crowded rebound behavior

How to Run

• Open ./physics_bounce.html
• Use a browser with WebGPU support, and check the help panel and HUD together with the sample when needed

webg Features Used

• WebgApp: initializes Screen, Shader, Space, Input, and Message
• PhysicsSpace: manages gravity, fixed time steps, restitution, friction, and sleep
• PhysicsNode: places dynamic and static bodies and resets velocities
• SphereCollider, PlaneCollider, BoxCollider: build collision shapes for the spheres, floor, and walls
• Shape and Primitive: create the meshes for spheres, floor, and walls
• EyeRig: handles the orbit camera and viewpoint control through pointer / keyboard input

Checkpoints

• Confirm that bounce height changes according to the restitution difference when spheres rebound from the floor
• Confirm that spheres flash red only at the moment of sphere-sphere contact and do not turn red for floor contact alone
• Confirm that the HUD displays the shared sphere resource reference count, making it visible that the sphere mesh remains shared even when the sphere count increases
• Confirm that moving the camera with drag, Shift + Drag, or the mouse wheel still makes it easy to keep track of the rebound flow across the whole arena
• Confirm that changing the sphere count with ?count= lets the same sample cover both lightweight checks and dense rebound observation

Controls

• Drag: orbit camera
• Shift + Drag: pan
• Mouse wheel / [ / ]: zoom
• Space: add 5 spheres
• P: pause / resume
• R: return the spheres to their initial state
• Add a URL parameter such as ?count=240 to change the initial sphere count

Implementation Details

• When you want to inspect restitution, friction, sphere-sphere contact, and sphere-box contact, this sample lets you read bounce height, red contact flashes, and reactions near the walls
• shared sphere resource refs is a useful indicator for whether mesh sharing in rendering is still being preserved
• Contract verification for PhysicsSpace itself is handled by unittest/physics_space_contracts, while this sample focuses on visible behavior and interaction