I reached the conclusion that… game should be constantly changing and should show always different result.
How to design this?
And if I want to control atomic level something, is it possible to show its result technically limited in Unity environment?
Atomic level simulation is completely outside of the realm of personal computing. For that matter for all practical purposes simulating anything of any meaningful size is completely outside of the range of modern computing in general.
To date the most complex simulation I’m aware of is the Hardware/Hybrid Accelerated Cosmology Code (HACC) which simulates approximately 1.1 trillion particles on one of the most powerful computers in the world (Titan).
http://io9.gizmodo.com/watch-the-most-accurate-supercomputer-simulation-yet-of-1462882295
https://en.wikipedia.org/wiki/Titan_(supercomputer)
However, despite how impressive that sounds, it’s worth considering there are several sextillion atoms in a drop of water which is at least one billion times as many particles as the above simulation and hardware are capable of handling.
of course always problem of density, we can compromise it up to just showing its core concept.
Not going to happen. We can only simulate ANYTHING right now on even the biggest super computers by taking major shortcuts, as @Ryiah pointed out. You’re going to have to cheat, and the less computing power you have, the more of the simulation you have to cut out.
I have a feeling that we’ll see Arowx’s AI that can automatically create games much sooner than we see a game physics engine driven by atomic level simulation.
But likely, we’ll all die before either of them to happen so probably it won’t matter much. 
Anyway, I think you might need to refine what you mean by ‘a game that constantly changes and gives different results everytime’ to get a meaningful feedback. There can be a whole lot of different games fall into that category: a simple slot machine game can gives you random result everytime and obviously it doens’t need any atomic simulations, for example.
Probably, at the other end of the spectrum, there would be such a(n imaginary) game where NPCs interact with each other just like humans do, in an environment where everything is possible, and that might actually require some technology of that complexity and magnitude.
But as art is always about ‘make believe’, and it doesn’t necessarily require molecular physics to devise some art that can give an immersive experience that makes people believe it’s something real.
So, you might want to refine what you mean by your ‘constantly changing game environment’, then probably we will see more meaningful discussions that can help you to confine its scope to a realistic level.
It’s simple you use procdeural generation and nested description of your universe such as only a few level at a small range is simulated. Using 91 (64 + 32, hierarchy in an octree like structure you have access to all particle in the known universe size.
Now you just need to be clever with your pcg procedure to ensure enough variety.
As a chemist I’m feeling a tad bit triggered by you calling it a “physics” world game.
I could talk a lot about how most atoms in a system aren’t really doing anything, so there’s little value in simulating them. mysticfall’s comment gets to the heart of the matter, however. What kind of game are you trying to make, and why do you think it would be better done with such a deep simulation of reality? If you can tell us that, we might be better able to suggest approximations that get at what you’re looking for.
I do chemical modeling of complex systems for research, and really the best I can do is a million agents. And they’re only acting on very limited sets of information - the 4-12 agents around themselves. And the simulation takes about a second to update. I have an i7-6700K at 4.0 GHz, which isn’t the greatest CPU out there but is pretty good.
You just have to make approximations. It’s an absolute necessity.
I am trying to make game that let users make them feel as he is Creator(or GOD).
Then it is similar like making Game Engine like Unity itself,
And at the same time, it should not be hard nor hard to learn, and need to be intuitive without any tutorial or description.
Then, it should be like small game engine.
I thought the best is Atomic level simulation.
But there is limits and scope, ranges inevitably because current compute power and my resources can’t make big.
But in a sudden boundary, with that user can create anything he imagine.
Good examples are Minecraft, Besiege and the game that make bridge between 2 points.(I don’t remember name)
So I feel that, now user can’t satisfy or become sick of with game that can have enormous numbers of combination possibility.
Instead, when the result of his choices and workout in game become near to infinite, I think he can feel excitement and fun.
But what do you DO in the game? Is it like Minecraft where you manipulate terrain?
So that is problem. At least it will not like those games, gamer don’t have interest in clone games.
So I thought first Universe or Nature creation in atomic level…
Computational power requirements aside this is a very good reason to completely throw out the idea. Very little about real life particle physics is intuitive or easy to understand without extensive assistance.
On the contrary gamers love clones. Check out this article about the sheer number of Flappy Bird clones. Between the author’s list of favorite entries and the actual image shown it’s very clear people do enjoy them.
https://www.digitaltrends.com/mobile/crazy-flappy-bird-clones/
It isn’t restricted to indie games either. Every single new Call of Duty is basically a clone of the previous Call of Duty with very minor adjustments yet the fans of the series continue buying them. Clones are very popular.
I think you first need to decide what you want the gameplay to be, then you can worry about going about achieving that. At this point it looks like you just had a vague idea and then attached a prerequisite (full chemical/physical simulation) to it.
What do you mean by nature creation? Terraforming terrain and then adding plants and such to it? none of that requires simulating atoms or even molecules (or even moles of molecules).
@EternalAmbiguity When I saw the chemistry and each atomic’s origins (born from the star impact, etc), periodic table, I imagined gamer control or make with some primitive atoms like H, O, C, N, and can combine, positioning it like real nature, the different result need to be shown to gamer.
@Ryiah So every new year, new Call of duty come out, but they have resources, powers to polish graphic, modeling, motions, system more. But I don’t have.
So only hope is game design.
And about clone game, maybe I am wrong. Maybe I am over hyped to make originality. But clone game need to be armed with more graphics or systems to get meaningful returns (money)?
Imagine you are at a nice looking beach that is about a few kilometers long. And you love the place so much that you decided to take that beach to your home and recreate the whole scenery in your backyard, by moving one sand grain at a time and placing it at the exact relative location of its original position.
I haven’t counted how many sand grains there are in a typical beach of that size, but there are about 7,000,000,000,000,000,000,000,000,000 atoms in a human body that weighes 70kg.
If you want your players to construct things like human beings by selecting and placing individual atoms, you are not making them feel like a god, but you are assuming they have god like abilities to play your game.
Maybe what you really wanted was an open world sandbox game with sort of an in-game world building feature, or some educational game that teaches how different molecules can combine with each other to form other substances.
But either way, I guess you need a more concrete version of your ideas before you can start thinking about technical aspect of actually implementing it with Unity.
@EternalAmbiguity So are you chemist? Then in atomic combination to make molecules, what makes real world difference? If some material consisted by O3N4 (assumption), positioning it also can make difference, right? Then why positioning it affect the physics? Maybe its because the powers of between atoms? Then are there any general rules of positioning? Position what amount of changing how affect to the real world materials?
@mysticfall Of course game design scope need to be scale down to lowest primitives.
Actually, it’s the other way around. You need more higher level of abstractions to make it feasible rather than reducing it any further to the lowest primitives.
Let me put it this way. A game engine is just a software that can be built from a source code, which is just a collection of text files that contain bunch of characters. So, does it make it any easier to create a game engine, if I say that “You can just type some words in your keyboard to create something like Unity. All you need to know is the correct order in which you press the keys”?
The fact that physical things can be decomposed into the lowest common denominator like atoms doesn’t make it any simpler to create a complex organism consisting of those units. Rather, you need more abstractions, or approximations that can capture the essence of your game mechanics.
I’ll reply mainly to your first comment here.
I guess my main issue is how meaningful this will be for the player. In Minecraft a player can make things like a building or a fort. Something very easy to understand. Or you can get into more detailed things like towns or whatever. Point is, it’s very obvious what the player is building.
What is the player building in your game? And furthermore, how does the player interact with the finished product to make it meaningful? In Minecraft, it’s fairly easy to understand what one can do with a house. A player can interact with it in normal ways (though I’ll admit I do feel Minecraft is lacking in this department).
Let’s say the player creates an oxygen molecule and two hydrogen molecules, making water. Now what? What do they do with that? It’s hardly as significant and personal as building a house, which is more like an art (in that it involves some personal expression, and has some intrinsic value to the maker).
To address your first post more directly: what are the players combining elements to make? And what do they do with those things they’ve made? The first question is more important.
@EternalAmbiguity
[what are the players combining elements to make?]
→ So the best is, different materials, substances that have different physics attributes. At least close to this.
More good is to show different shape based on molecule level’s some combinations.
[what do they do with those things]
→ There is maybe not much to do with that. Just seeing it can be felt the result he got.