[Project] RTS game engine : OpenRTS is released

Awesome! :slight_smile:

1 Like

Beatiful! really.

1 Like

Thank you for all your encouraging messages ! Don’t hesitate to like and comment the video on youtube, it helps.

I think that the project as come to a stage. Now it needs some content to continue and I don’t know if we will have the courage to create it. From now, it must accelerate or stop completly.

We will see what happen :smile:

What?? You did the “hard” part and think of stopping before starting the “fun” part?
Please either finish the game or release a jMonkey plugin of it! :stuck_out_tongue_winking_eye:

1 Like

Remember that the goal was to make an RTS game engine, not a single finished game. The “hard” part was the most interesting for me and there is a gazillion of things to do to make something workable.

To create an engine, I guess I have to build at least a “test game” too. To be confronted to the real needs. To discover the essential features it has to have.

So yes, the solution may be to put it on a public Github repository, or to publish it as a jMonkey plugin and let the interested persons make that work. But for that, I have gazillion of doc to write :smile:


That’s reality browski! Do eeeeeeet! Just do a simple repo with your code first, no plugin. Changes are coming on that front very soon.

Maybe after we’re done with the first jME Example Game we could see if anyone’s interested in taking the lead on a 2nd one using your RTS editor.

1 Like

Hey @methusalah,I am working on a RTS game of my own.
(Sorry this being my first post I could not post the images)
Being a school student I am having some problems,since you said:

Can you help me with these implementations:

  1. I want a grid based world with tiles with heightmap support
  2. I want to drag select multiple units and want them like this with health bar when selected:
    3.And mount the camera at this angle

Please look at post no. 34


There are tons of implementation for a grid based map. My advice is to create

  • the class Map extending an array of Tiles.
  • the class Tile, generic, with only two Integers x&y and a reference to the containing Map.
    Then you extend Tile for more specific class like Ground with z coord, Cliff with ciff shape, Water, etc.

Map contains all exploring method. Here are the main :
getTile(x, y) returning array.get(y*width+x)
getNorth(tile) returning getTile(tile.x, tile.y+1), same with south, east, west (and if needed northWest, etc.)
get4Neighbors(tile) returning new array with getNorth(tile), getSouth(tile), etc.
get9Neighbors(tile), including tile

Tile should have it’s own getNorth, getSouth… it’s less verbose.

This basic structure allow you to explore the map without visiting all elements at each time.

Selection area is simple to implement with jMonkey. At mousePressed you store the ground coordinate pointed by the mouse, and at mouseReleased again, then you have a bounding box. You search in your unit list the units that lie inside. Later, you will want to deform this bounding box according to the camera frustum and to follow relief, but it’s not priority.

This is easely made with jMonkey, by extending the class ChaseCamera. You lock the mouse view, set cursor visible, set the camera angle and position and it’s done. Then you bind your WASD or arrows to affect x,y coords of the camera.
For more exemples : http://wiki.jmonkeyengine.org/doku.php/jme3:beginner:hellochasecam

If you need more info or piece of code, please contact me by PM.

God luck for your project !


1 Like

Hi Methusalah,

I don’t know if you are still answering questions on this topic but I just came across this yesterday. What you’ve written is exactly what I’m trying to write for my own RTS game. I have a couple of questions I hope you can answer.

  1. In your video I see that the wireframe grid changes height to match the rise of the cliff meshes. Is that grid used for calculating your flowfields?

  2. How are you implementing the terrain painting? I know that the textures are seemless and your painting an alpha to reveal the different layers. Is the alpha channel one big texture? How big is it (2k x2k)? Assuming your using GLSL for your graphics, could you share your code or sections of it?

  3. Do the cliff tops and ground share the same UVs? In other words, as you draw the cliffs on the map, does the tops aquire the same UV’s as the ground they replace?

  4. I’m really interested in how you’ve written your editor on a technical level. Please consider posting more detailed info about things you’ve discovered along the way.


Yes, the ground is made of tiles. Each node as a height to create relief, and each tile store a moving vector given by the flowfield.

jMonkey helps a lot with that : http://wiki.jmonkeyengine.org/doku.php/jme3:advanced:terrain, “Terrain Splatting” part. It explains all you need to know to draw the good texture at the good place. jMonkey can make a texture from a ByteBuffer. Here is my code to create a ByteBuffer from my layers :

    ByteBuffer res = ByteBuffer.allocateDirect(width*height*4);
    int firstMapIndex = index*4;
    for(int x=0; x<width; x++)
        for(int y=0; y<height; y++){
            int r = (int)Math.round(layers.get(firstMapIndex).get(x, y)) << 24;
            int g = (int)Math.round(layers.get(firstMapIndex+1).get(x, y)) << 16;
            int b = (int)Math.round(layers.get(firstMapIndex+2).get(x, y)) << 8;
            int a = (int)Math.round(layers.get(firstMapIndex+3).get(x, y));
            res.asIntBuffer().put(y*width+x, r+g+b+a);

The tricky part is to create the atlas (the set of layers). At each coordinate, the sum of all layers must be between 0 and 1. Layers must be linked. Here is an exemple of this link :

private void increment(Point2D p, int layer){
    double valueToDitribute = incrementVal;
    ArrayList<DoubleMap> availableLayers = new ArrayList<>();
    for(DoubleMap l : atlas.layers)
        if(atlas.layers.indexOf(l) == layer)
            valueToDitribute -= add(l, x, y, incrementVal);
    while(valueToDitribute > 0 && !availableLayers.isEmpty()){
        ArrayList<DoubleMap> unavailableLayers = new ArrayList<>();
        double shared = valueToDitribute/availableLayers.size();
        valueToDitribute = 0;
        for(DoubleMap m : availableLayers){
            valueToDitribute += subtract(m, x, y, shared);
            if(m.get(x, y) == 0){
private double add(DoubleMap map, int x, int y, double val){
    double rest = 0;
    double newVal = map.get(x, y)+val;
        rest = newVal-255;
        newVal = 255;
    map.set(x, y, newVal);
    return rest;


In my code yes, when you place a cliff, the ground is “cut”, but it always uses the same mesh, the same texture atlas and the same UV space. It may be a problem with overhang cliff style, because the ground texture at the top and the bottom share the same 2D coord, and the same painting.

The most hard part of the editor was definitly the cliffs layout because there are tons of special cases. My main regret is to have placed cliffs on the tiles, not on the nodes. It has made everything much more complex (but also more permissive).

When I finally fully understood the mechanism, it was too late to easily refactor, so if you intend to create a cliffed tile map like Stracraft, I would hardly advise you to study that part very well :smile: I can provide more explanation if needed.

Good luck with your project and do not hesitate to ask pieces of code.


Hi Ben,

Thanks for taking the time to get back to me.

In my current build I’ve got a set of basic building block meshes that form two levels of platforms and one level below ground that is unwalkable. I’m in the thick of writing the code to place the correct block on the grid based on whats already there. Not hard, but slow going. I can’t think of a way to make it procedural so I’m doing it brute force. A block is choosen based on the surrounding blocks, etc.

I’d like to get your thoughts on placing your cliffs on tiles verses nodes. What were the pros and cons?

I’ll try to be clear but it’s not garanteed :smile:

First a naming precision : I call node’s height the value that make the relief of the ground, and node’s level the elevation of a node regarding to neigbboring nodes, delimited by cliffs.

Blizzard’s approach :
Each node of the map has i’ts own level.
You can elevate one single node. Then you will have four cliffs: north-east, north-west, SE, SW. The cliffs will all have the same shape : salient.
If you want to elevate more nodes, they will be managed by group of four, snapped to pair rows and collumns of the tile map. See the left scheme above. The editor will also round the inner corners (“o” on the scheme).
The right scheme is impossible to do.

b b a a        x x x x x x
b b a a        x x x x x
  o b b            x x
    b b              x

The surrounding tiles will all have a cliff mesh, straight, corner or salient.

This approach has three advantages :

  • every configuration works at creating a correct cliff path (chain of continuing cliffs), there are never any bug,
  • straight parts of the chain have always a pair nomber of cliffs,
  • diagonal parts are assemblies of the triptych “salient/corner/salient” elements.
    It ensures no bug and very few different shapes for all cases : couple of straights, lone salient, diagonal triptych.
    But there are tons of cliff path that are forbidden. The pair snapping is not intuitive in the editor and it may be frustrative to be unable to achieve the vision we have in mind.

My approach :
The level is stored on the tile, and given to the four connected node. When you elevate a tile, you get 9 cliffs : NE, N, NW, E, W, SW, S, SE.
But you can elevate any tile regardless of the surrounding tiles. No snapping.
This approach allows any cliff path, especially good for narrow and tortuous canyons.
But it also generates bugs. In the video, you can see red blocks when sculpting cliffs. These are detected bugs that mus be manually managed. Look at that scheme for one of the many cases :

x x x x
x   x x

The empty tile needs a cliff, but the five surround elevated tiles ask for a different shape and there is no solution.

Also, in this approach, you doesn’t ensure to have grouped cliff and this lead to thin and repetitive elements. You will want to detect couple and triptych as well, but you will need more different shapes to cover every case.

Hope it helps !


This would indeed be very awesome to have as an open-source community game. Count me in on contributing art assets if this is released under a FOSS license!

1 Like

Hi Ben,

Sorry I didn’t reply sooner. Thanks for the detailed answer about the mapping of geo. I’m actually taking the Blizzard approach for my editor. In fact my first pass was just as you described…

b b a a
b b a a
  o b b
    b b

I then realised the exact issue you brought up. I changed my mesh tile sets to allow for…

c b c
b a b
c b c

where c represents corners. I’m checking in eight directions around the placed elevation and comparing each piece against what is currently on the map. Then I have a lookup table to determine the appropriate mesh tile to set at that location. The lookup tables size isn’t bad, and I’m implementing a way to have multiple meshes for each tile that would get randomly chosen. This way I can have different meshes representing a corner and it helps keep the map from looking too repetitive.

It’s a long way to go so… good luck !

yes I think that I will do that but for a first releas, I have doc to write and tons of other things to do for now :smile: maybe in a few months

Ok, great :wink:
Although realistically speaking you might forget or be distracted otherwise and if you released the code now people might help with the docs (a wiki + issue tracker is very easy to set up on the github code repository) or at least have a start at hacking right away. But it is totally up to you of course.

1 Like

I just realised only half my message was posted. Check above for the complete post :slight_smile:

OK this is decided :

The project becomes open source !

To be honnest, it is already on a github repository since the beginning (in stealth mode :smile:)
Now I will communicate, invite contributors, create a wiki/forum/doc for the community to use it if possible !

All graphical content is also open source, with the kind authorization of Draax, it’s author.

Some textures are not free to use (quickly grabbed on Internet for testing purpose) and will need to be replaced.

Of course, I will need help and the first question is : what name to give to the repository?

  • OpenRTS?
  • OpenCraft?
  • arg ! lack of ideas…

While you make proposals and debate, I will began the wiki.

Thanks to all of you for your enthusiasm !



Awesome, time to look into asset import for jmonkey engine :wink:

Freecraft/Opencraft are kind of “burned” names since the Blizzard legal action see: http://en.wikipedia.org/wiki/Stratagus

Random name ideas: jStrat, Jarts, Stratava, hmm Farts? :wink:

1 Like