Aaron Franke aaronfranke

Aaron Franke

I am working on a standard for specifying parameters for rigid body physics. This standard needs to support multiple physics engines. I already have parameters for the body's mass, linear velocity, and angular velocity. I need to add a new parameter for the inertia tensor, which describes the body's resistance to be rotated in different directions. The problem is that some physics engines implement the inertia tensor as a 3x3 matrix, and some physics engines implement inertia as a Vector3. I am thinking that I should specify the parameter as a 3x3 matrix, and include algorithms to convert to and from Vector3 inertia to support those physics engines that use Vector3 inertia. What is the formula to do this? Also, can you evaluate if my approach is portable?

ChatGPT

Your approach of specifying the inertia tensor as a 3x3 matrix and including algorithms to convert to and from Vector3 inertia is a good way to handle the variability in how different physics engines implement inertia. To convert be

	# IEEE-style floating-point format table generator (Python)
	# Python version: https://gist.github.com/aaronfranke/0d1217e521c4ec784d39e92b5f039115
	# GDScript version: https://gist.github.com/aaronfranke/8b2c39bfbe48068c574e4daf2710c875
	import copy

	# SEMB values can describe any IEEE-like binary floating-point format.
	sign_bit: bool = True
	exponent_bits: int = 4
	mantissa_bits: int = 3
	## Can be set to an integer. If null, the bias will be automatically determined

	# IEEE-style floating-point format table generator (GDScript)
	# Python version: https://gist.github.com/aaronfranke/0d1217e521c4ec784d39e92b5f039115
	# GDScript version: https://gist.github.com/aaronfranke/8b2c39bfbe48068c574e4daf2710c875
	extends Node

	# SEMB values can describe any IEEE-like binary floating-point format.
	var sign_bit: bool = true
	var exponent_bits: int = 2
	var mantissa_bits: int = 1
	## Can be set to an integer. If null, the bias will be automatically determined

	// Here are three of the cases:

	case Variant::VECTOR2: {
	Vector2 val;
	if (type & ENCODE_FLAG_64) {
	ERR_FAIL_COND_V((size_t)len < sizeof(double) * 2, ERR_INVALID_DATA);
	val.x = decode_double(&buf[0]);
	val.y = decode_double(&buf[sizeof(double)]);

	if (r_len) {

	#!/usr/bin/env bash

	# This script bulk-renames many things in Godot 3 projects to hopefully
	# make it easier to convert them to Godot 4. The goal is to do as much
	# replacing as possible here so that the diffs Godot produces are smaller.

	set -uo pipefail
	IFS=$'\n\t'

	# Loops through all text files tracked by Git.

	* System information from steam (`Steam` -> `Help` -> `System Information`) in a [gist](https://gist.github.com/):

	Computer Information:
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	Form Factor: Desktop
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	Processor Information:
	CPU Vendor: GenuineIntel