WeightSTool creator

First time poster, so excuse any mistakes I make!
I’m a third year university student studying BSc (Hons) Computer Games Developmeng in England. For my third year project I am comparing the physics in the Source Engine with that of real life. I’ll be doing this by creating a Rube Goldberg machine in Garry’s Mod.

Now for the question! I searched everywhere for a STool that would allow me to measure the weight (or mass) of a prop for use in equations, and the only one I came across that works is the WeightSTool.
I originally downloaded this from Blaknite’s tool pack availble from:

Blaknite informs me he is not the creator of the included tools, and to search here. So I suppose I’m really asking if anyone knows the creator of this mod. If they don’t does anyone know a working STool that allows me to see the mass of a prop.

In addition, are they any mods (on infact ingame console commands or methods) that allow me to measure other physics related properties of props?

Thanks in advance, any help would be greatly appreciated. And any sources will be completely & correctly referenced.

Have you checked the files? Addon creators usually sign their stuff, and since Lua is compiled on runtime, the scripts can be opened in any text-editor.

The info file inside of the Weight Stool folder says Spoco. Here is the link to the page.


I don’t believe the units of meaurement in the source engine actually conform with real life units. I believe they’re just Pseudo-units, basically I’m pretty sure and objects weight isn’t given a weight in say pounds, or grams, etc. If I’m correct in saying that the source engine simply uses a range of numbers to designate weight, instead of using the metric or imperial system.

Either way, the source engine often disregards realism when it comes to weight, for example, spawn a huge model bridge (somewhere in “useful Construction”, I think) and drop it from very high in the air (noclip), and observe how it slowly floats down, like its travelling through water. While the source engine is realistic, the end result will not be the same as real life, as several essential laws are not present in the engine, i.e airodynamics, thermal dynamics, etc, and the many other factors that effect real life.

While it may look similar to life, on paper, you’ll get drastically different results than what you’d expect.

I understand the units of measurement are arbitrary, however they are uniform across the engine. Which means a SI of units can be taken and used uniformly in comparative equations. And I feel I’m going to prove that it’s drastically different from real life.

Thanks for the response, guys! Much appreciate!

The bridge was never meant to be a physics-enabled prop. It’s mass is 1. All props do this with a mass of 1.

Simple commands for measuring or setting mass:
lua_run Entity(1):GetEyeTrace().Entity:SetMass(100)
lua_run print(Entity(1):GetEyeTrace().Entity:GetMass())

Shit your right. I totally forgot that its mass was 1, lol.

You can get all the properties by using a basic lua script. You can find most of what you’re looking for, including mass, here: http://wiki.garrysmod.com/?title=Physobj

The standard length unit in Gmod is referred to as a “unit” - equivalent to 0.75 inches.
Mass is in units of kg. Time is almost always in seconds, and physics timesteps/ticks occur every 1/66 s by default. Source uses the standard quadratic drag equation to simulate viscous drag in air and water, based on the physics bounding box of the entity. Prop interactions use the basic equation for inelastic collisions. Everything should be easy to figure out, it’s all basic stuff. Source forces are all based on real world equations, so the only things you’ll find differ a huge amount are basic constants like gravity and air density, and they can mostly be changed by convar. Like most physics engines though, Source doesn’t have any concept of heat, so any energy-based equations will go out the window. It’s all just forces.

How come you picked Source though? Why not try finding an open-source physics engine where you can just peek at the code directly? I doubt the physics will differ all that much, I don’t think Source does anything very special (besides screwing around with crazy units).

If you still need a stool to tell you the weight and to set the weight of props, Just post back here. I could make one for you =/