Combat AI, Navigation and Screenshots

So recently I've been looking at my combat AI, so far I've made do with it getting so close to the player and sitting still and shooting until the player moved out of range, it lost sight of the player or the player killed it. That's not good enough though, in terms of game play it is really predictable and lacks any sort of adrenaline or challenge. Well unless about 20 of these enemies surrounded you and just opened fire.

Of course this was just a temporary combat mechanic designed more for testing other functionality such as line of sight, my finite state machine and weapon controls. But now the time comes for something more advanced.

Initially I thought about terrain analysis and tactical assessment on the fly, something I'd be forced to do if I was working with robotics or something more physical but that idea rapidly gave way to storing valuable information on the map.

So to my scene I added a node named "Cover" to this node all objects that could be used as cover would be attached, things like crates, sandbags maybe a table. Things to obscure the line of sight but still allow the AI to shoot at the player. This list of cover objects would then be loaded and stored in an object designed to provide global information to the NPCs. An object which could also be used to relay communications between troops alerting other allies if they have a man down and should be on alert for the player. But enough of that I'm getting sidetracked (maybe if I updated more regularly I could have wrote about this in another post).

So I had my cover list and I changed the finite state machine to get the AI to put cover between it and the player upon sighting the player. And one thing became clear. The player just walked through the cover.

So I regenerated my navigation mesh trying to get it to account for static scenery and found that the JMonkey navmesh (which in turn is a wrapper for a previous version of the critterai library) doesn't factor in other models for the navmesh.

Right now I saw two choices:

1. Edit the source code to fix this
2. Use the navmesh pathfinder for a generalised path then tweak this dynamically to avoid obstacles

Upon looking at the source I decided to go for option 2. Plus it would allow for objects to move from start position which is definitely more flexible.

So how to do this...

Well here goes my method.

I cloned the bounding boxes of all cover objects as you can't get dimensions from models directly. I then added the radius of my AIs collision shape to this. The reason for this is when checking if the AI can fit between two obstacles its easier to expand the bounds for the obstacle and shrink the AI down to a point with an infinitely small width. 

Then any overlapping bounding boxes I merged as the AI couldn't fit between those two obstacles. I then performed ray casts between each pair of adjacent way points on the path checking for intersections with the bounding boxes.

Any bounding boxes I collided with I took the position of the midpoint of the segment of line that intersected the box. Then I created a vector starting at the centre and moving to the midpoint and extended that by the width of the bounding box. 

For a tighter fit I might want to perform another raycast to find the edge of the box were the character can walk and just brush the sides of the obstacle (remember I extended the bounding box) but for now I'm happy with this fix. It's still a work in progress and I've still got to fully test how far I've built before optimising it.

So without further ado a screenshot. The blue box is the AI, the grey box some cover, the pink dot is set above the centre of the bounding box (which is invisible), the cyan dot above the midpoint. And finally the red dot is the detour point to avoid hitting the cover.

The green line I drew in to show the ray going between the end way point behind the cover and the one prior to it.

Cor' blimey check out that FPS!

Now because I don't want anyone to think that because of the ugly character I made last entry I'd forsaken the human race and shifted my allegiance to the people of cube here is a screenshot of my last player texturing effort:

I'm quite proud to say it, the skin was made in photoshop by brush. I used these brushes and followed the tips http://www.brusheezy.com/brushes/1752-skin-textures-v1 they've also made my clone brushing look smoother can't recommend them enough!

Finally! A "Properly" Textured Human

Well I've done it, through the power of youtube I've managed to find a good way of texturing humans. No more trying to paint onto meshes or UV layouts desperately trying to achieve the accuracy needed despite the bumps and protrusions of a human body. No more labouring under the hot sun looking for a friendly face and despite my efforts being confronted by grotesque homunculi.

By projecting from view (with bounds) I create a UV layout of one face of my model. I then apply a normal picture of a person as the texture texturing that side of the model. With the clone brush That single side is painted onto the corresponding area of the full UV layout.

Tis truly a thing of beauty. I take this simple man: http://fanart.tv/fanart/tv/248834/characterart/last-man-standing-2011-4ffb175969e71.png

I then apply him paint and I achieve:

Now naturally I won't use this man in the game and all rights belong to whomever took that picture. And the texture was only just lined up but it looks bloody good. I'll try and find some models to take photographs of or create my own computer graphicsy people that are of comparable quality to the resolution blender paints at and then huzah. The people are done.

Of course credit were credit is due I wouldn't have done it without this great tutorial:  http://www.youtube.com/watch?v=p4ngVoGIj1Q  

Now naturally this wasn't as easy as it seems, something had royally messed up in blender and I couldn't see the clone brush but by linking my scene to a blank project I was able to use the clone brush without having to burrow into blenders settings and find out what had gone wrong.

So Pretty.

Textures are wrapping correctly, and animations exporting correctly, the next stage in graphics is to make some nice textures for characters.

However my art skills may not be what they once were:

Hey good lookin', whatcha got cookin' ?

It's nice to see real progress is being made, I feel half of the work left on the game is polishing it up to add that professional touch.

A Brief Update

Recently I've been working on getting animations into my characters in a bid to finish off the game art. So I made a basic walking cycle and imported the model into JMonkey, this however didn't work, for some reason the animation control wasn't attached.

After examining the model I concluded that the UniHuman skeleton wasn't valid for JMonkey (no root bone at 0,0,0 and it may have used shape keys instead of bone animations). I don't know if it did have bones as blender wouldn't display them (and yes I did set the armature to x-ray). So I deleted the rig and started again making my own skeleton something there are plenty of resources on and is dead easy.

So I re-rigged the model, animated, exported. Still nothing.

After some hunting around the JMonkey forums I found that the general consensus of the community is that the blender importer doesn't support animations. There were one or two people who said they did it and it worked but apparently followed the same steps the rest of us were following. So I tried to export using OGREXML.

The result made me want to gouge my eyes out. Bow legged, stumbling, it made Peter Jackson's early work seem restrained and rather pretty. I tried to fix the rig but it didn't go well so I deleted it and re-rigged, 46 bones later and scale and rotation applied I had a working animation.

Now animations work perfectly, unfortunately the texture is really messed up my .material file seems to be doing naff all except for putting the face on the upper thigh.

I've also made some alterations to my autonomousMovementControl class, copying useful fields over to separate lists to garbage collect larger items away earlier, also removes the overhead of calling methods and makes the code more readable. (path.get(i).getPosition() vs path.get(i)).

I'm beginning to get frustrated with computer graphics, but it''ll be worth it when I have a game under my belt.

Enemy AI (Finite State Machine and Line of Sight)

So I feel that I've made great progress recently, characters are up (unfinished) and the AI is coming along great. I've taken my initial prototypes of various functionality (line of sight, path finding) and migrated them to a finite state machine.

Each state is a singleton and they share a unified interface with the methods CheckConditions, Start, DoAction, End. They all take the spatial they are controlling as an argument. The actual state machine is implemented as a controller attached to the character, so using the spatial the states can get access to the state machine and other controllers.

The reason I chose the singleton pattern is that when using a lot of characters I didn't want to have to create 3 states for each character and the singleton avoids this overhead, plus with the spatial it is commanded inputted as an argument it is able to do everything I need.

So without further ado I'll go into detail about the methods:

CheckConditions(Spatial spatial): this method checks if the conditions to enter the state are true or not. So when in the patrolling state AttackState.checkConditions(spatial) will be called and if this returns true, the next state will be the attackState meaning the spatial will attack. This method is also used inside the AttackState class to check that it can still attack, if it can't it will move back to patrol and set the place the player was last seen as its first patrol point.

Start(Spatial spatial): this method runs any start up logic necessary to move into that state, this includes and is not limited to animations for the character.

DoAction(Spatial spatial): this works out what the spatial should do and sets it to do it, its also responsible for moving to other states if the conditions are correct

End(Spatial spatial): runs any ending animations or logic.

Line of sight

Early on in the AI line of sight was one of the first things implemented, using the AIs view direction we find the angle between straight in front of the AI and the players location. If this is outside of the field of view then the AI can't see the player and this is demonstrated below:

Red line dictates field of view, green and red triangles player and AI respectively

If the player is inside the AIs field of view a ray test is then done from the centre of the AI to the player. This ray test will collide with the AIs geometry so if the number of entities the ray collides with is greater than 1 there is a geometry between the AI and the player, meaning that the player is obscured from view.

Right now this system just returns true or false however I am planning to implement a 2D Gaussian function so that the AI is more confident the closer and the nearer to the centre of vision the player is. This will mean that when the player is a distance away and creeping around the outside there will be a chance he/she remains unseen. Then the response of the AI can be dictated by numerous factors such as: aggression, fear or other emotional scores I could give.

This is a stretch goal, however my AI can see the player and move between states, it can effectively move between attack and patrol and respond in a semi-realistic manner. Now it's just a question of tailoring the system and augmenting it - something relatively easy with the highly modular system I'm using.

All in all very happy =D

Texturing

So far with my game I've been representing characters with cubes, these cubes move around, shoot, and change colour when you enter their line of sight. But a big part of the game and something I see being one of the most complicated for me is graphics and animation. Because of this a desire to get the basic animating of characters and importing into the game has preyed on my mind.

Initially I was trying to use makehuman to make my game characters, it was fully rigged textures included and had a very open licensing agreement, yes it did make very high poly characters but I was sure in blender I could decrease the vertex count and optimise it. However I had a lot of problems trying to move the models into JMonkey, as you can see below:

This took a lot of work to get to, initially I started off with a fragment of torso with some random pixel clusters. I know of people who have apparently just exported, put into blender and imported into JMonkey with little trouble so I don't know if there's something I missed or they're using the nightly builds or an older version.

I was beginning to reach my wits end, at one point I half considered scrapping JMonkey and giving unity a shot. Luckily however I came into contact with unihuman ( http://goo.gl/OrTl7 ). I opened up the blend file, selected the model and pressed shift-f10. This unwraps the model to create a UV-Layout:

I exported this and whacked it into gimp where I painted it (albeit terribly). I then created a material and added a texture to it. The screenshot below shows the textured model along with the mapping settings. The texture is mapped to the UV layout because other wise the image file is laid onto the back and the rest of the model filled in with a solid colour:

I use the jmonkey blender imported and add the material file to the model programmatically, when the model is finished and animated I'll be able to use it for nearly every character and just provide a different texture file.

The finished result in the game world is:

As you can see the texture is a bit terrible (great art skills on my part), but I used to do a lot of photoshop and eventually I'll take the time to properly texture up the model. Right now I'm looking at animating the model either from scratch or using open source mocap data.

Overall I'm quite happy with this. It might be overly optimistic but I feel that characters are the hardest 40% of the art work, and they are a part that I have near enough got down.

Spawn points and map data

So lately I've had a bit of a conundrum, how do I save level data so that when I load the scene I can get things like player spawn points, patrol areas etc. My options as I saw them were:

• Find a way to place the data directly onto the map
• Save it into another file i.e. <level_name>data.xml and create a map editor that synchronises the two.

Naturally the second one isn't the best option, there is always the chance the two could become out of sync and the level won't be correctly loaded the first is far better. And before I go on a brief introduction should be given on Spatials vs Nodes vs Geometries:

• A Spatial is an abstract class that contains all the data and base methods for nodes and geometries. You can store things such as position and rotation in a spatial.
• A Geometry is an extension of a spatial except it represents a visible object in the scene graph
• A Node extends Spatial is a handle for other Spatials, it can be used to group objects in the scene graph

So initially I wanted to add a nodes to the graph to represent data, there would be a parent node called something like spawns and all it's children would have a local translation set. However in the sceneComposer in the jmonkey SDK there isn't an option to add a node to the scene. But there is an easy workaround (credit does go to Normen from the JMonkey community for the inspiration behind this):

In the models folder in assets save a new jmonkey scene (.j3o file), however don't create a model for it leave it blank. The empty space for the model will have an origin, and we can place this empty model in the scene and use it to store information. If you don't understand double click on the file and see the picture of the axes. Well when we place this empty model the origin of these axes is our local translation. We can place these blank models around the scene and get their location and this is how information is being saved into the level. I won't go into how to add these models to the scene this is covered adeptly on the jmonkey website.

These models will be added as a child to a node added to the scene graph. I called this node "Spawn points" and loaded the list of spawn points with the following code:

Node spawnList=(Node)((Node)level).getChild("Spawn points");

for(Spatial s:spawnList.getChildren())

{

    ArrayList<Vector3f> spawnPoints.add(s.getLocalTranslation().add(0,4,0);

}

The add(0,4,0) is there to prevent spawning a character at a point were it can fall through the map. There's no need to make additional blank models of course, you can infer the purpose of the spatial by the name of its parent node.

Of course this doesn't solve the patrolling issue but I have a number of ideas:

• Using none blank models the patrol zone being inside them
• Points defining the area, the patrol area is a concave polygon encompassing all the points
• Other more inventive method.

As I see it now the point based method has short comings based on the difficulty of specifying a awkwardly shaped patrol zone, and multiple patrol zones. Also the model method has problems, storing a large amount of different shapes that aren't even loaded adds an overhead to the project. I'm not attempting to prematurely optimise but while this isn't a pressing concern there's no harm in mulling it over until an elegant enough solution presents itself.

I've also attempted and successfully created and animated a human figure in blender + makehuman I'm going to work on some more pressing essentials before I start figuring out the best way to export/import these assets and control the animations. These are likely going to be timely operations given my inexperience with graphics and I have other things to focus on.