Turing Sim: Contact Forces You Can Actually Read

Each touching pair now gets one named arrow: who pushes whom, and how hard.

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Before

After

Before: one unlabelled peak reading. After: the two pads each pressing 21.2 N on the cube.

Before

After

The panel lists named pairs and says how to see every push on a body.

Situation

Turing Sim can draw contact forces while physics runs. Before this change every contact point got its own arrow, and the only label was the strongest force. Holding a cube with a two-finger gripper produced a yellow cluster with "2.78 N" next to it. You could not tell which finger pushed, how hard each side squeezed, or whether a robot's own links touching each other were drowning out the contact you cared about.

Task

Make the overlay answer the questions people actually ask when a grasp misbehaves: who is pushing on this body, in which direction, and how hard? It also had to stay readable on a hand with many links, and work the same in the Storm and the native Metal viewports.

Action

1. One arrow per touching pair. Contact points are grouped by the two bodies involved. Each pair draws one net-push arrow ending at the force-weighted centre of its points; small dots still mark the individual points.
2. The selection decides what is shown. With nothing selected, the strongest pairs are labelled "left pad → Cube · 14.5 N". Select a body and every push on it is drawn, each oriented onto that body.
3. Internal contacts are separated. Contacts between parts of one articulation (two fingers of one hand, the pieces of a puzzle cube) are hidden unless "Include self-contacts" is on, so they never crowd out the rest. MuJoCo and Genesis both report which tree each body belongs to.
4. Details on hover, and glows. Hovering an arrow opens a card with the pressing and friction components. The native Metal view now forwards pointer motion so this works in every viewport mode. An optional glow marks each point, cool to hot with its force.

The commit was tested in isolation: 88 tests passed.

Result

The captures show the same grasp before and after. The old view had one unlabelled reading; the new one shows the right and left pads each pressing 21.2 N on the cube and a follower link touching it at 2.42 N. The Robot panel lists the same pairs and points to selection for the full picture.

This is a debugging aid, not a measurement tool: the numbers are whatever the engine reports, and the two engines still differ.