Anyway, the game has a name.  The new game is called iPlutoid.  Now I know there are some people that hate the ‘i’ on the front of iPhone games, but it seemed to kind of work, so iPlutoid it is.

Just before the game goes into beta test, here is a new video.  Apologies for the poor quality of the actual iphone footage, but its real hard filming accelerometer based games.  Anyway, I would enjoy hearing any comments.

Along the way, some of the ideas have been put back, just in order to get the first release out.  The development would have taken an awful long time if all the ideas went in the first release.

anyway, the vid …

Here is the first draft of the icon for the game.  Let me know what you think.

heres my spiky pod-style enemy – turned out quite nice.

Just recovered from a weekend away in portugal with the boys, and from the resulting swine flu (ok may have just been a cold) that I got from wandering the streets in just a shirt at 5.00am ! So I promise more frequent blog entries from now on

If you look carefully, you can see the targeting system in operation. It’s only showing the first level, so there are only a few enemies and they are pretty tame, but it gets a heck of a lot more involved on the later levels.

I will add more gameplay videos over the next few weeks, and more blog entries regarding the gameplay mechanics and AI.

enjoy.

I will talk more about the gameplay in a later post.  Not going to publish a video yet, as that will come when things are nearer completion.  There will be a single player mode to start with, but I am already conceiving of a multiplayer mayhem dogfight over wifi.  You won’t believe how fast everthing zips along.  Love it !

Moving an object around a sphere sounded very simple. However when I came to do it I wanted to be able to turn objects, left or right, relative to their current heading. It then became a bit more complicated. I started off using angles, theta and phi, to represent position but this has problems with Gimbal lock when converting to Cartesian Coordinates. Trying to move was also difficult, determining which angle to change is dependent on current position. i.e. When travelling North (decreasing phi) and you cross the North Poll you are now heading South (increasing phi) and theta has increased by 180 degrees. The result of which was to go to Quaternion maths.

There is a lot of stuff out there about the use of Quaternions in 3D games, and whether they are necessary, so I won’t try and repeat any of it here. I found that I could use this method of storing position and heading very efficiently. So now, all objects have their position held as a quaternion, with their current heading held as two further quaternions. Simple multiplication of these quaternions moves the object along its current heading. Changing heading simply means recalculating the two heading quaternions. There is no Gimbal lock and all objects can move relative to their position and not the underlying coordinate system.

The first method, and still used in some places, was to generate a bounding box around the target and then to see if the shot was within the box.  Remembering that the XYZ of an object is no longer the same as the XYZ of the drawing system.

Having generated the Up, Left and Forward vectors, or Normals, of our object I can now calculate the bounding box.

To determine if the shot is within the box is a simple dot product of the shot position against the Normals of the each box face.  If the result is positive it is Outside the face, if it is negative then it is Inside the face.  If all faces report Inside then I have hit the target.

After developing all the code to do this I then realised there was an optimisation that further reduced the calculations.

The Normals for the box faces were already calculated, these are the Up, Left and Forward vectors used to generate the bounding box.  This was then further simplified by only needing to calculate and check the dot products against two points of the bounding box on opposite sides.  Now one set of dot products has to report Inside the faces and the other set Outside, this saves flipping the Normals.

Anyway, the point of this post is about aiming and shooting.

A lot of 3d games have crosshairs that you place over a target and shoot.  Well those games are not using a 3d missile path for shooting stuff, as evidently if you place cross hairs over something far away and shoot at it, then if something is closer to you on the same diagonal path as the missile is about to follow, then it would also get shot, but the cross hairs can only be over the one target !   My game is true 3d shooting, so I wanted to come up with something different.

I decided that having a HUD style interface that highlighted each enemy on the screen and then indicated to you whether you were either vertically or horizontally displaced from hitting it with a missile would be quite cool.  Having played it, it is still fairly difficult to hit stuff in 3D, but it does seem to work.  Afer all, this is a game, not a simulation.  After playing for a  while, you kind of get your “eye in”, and start shooting stuff naturally.  I am fairly happy that this is the way to go rather than cross hairs.

I like to think the Lighthouse looks so cool on my small planet, that I will feature it specially somehow.  Don’t know how yet.

Oh, another cool thing, when a “lander” for want of a better name at the moment, takes a human from a house/windmill, and reaches an arbitrary orbit level, it will “mutate” as per defender, but also shoot a laser bolt down to the house below, desroying it, “independence day” stylee

Now the maths for this is all getting pretty hairy, but I will make a future blog about the use of Quaternions in all this.   Heavy going, trust me…..

To give you some kind of idea of how far behind, the blog of the game is, behind actual development, I was writing a particle object last night for the explosions   Everything is coming along very very nicely !  Have I mentioned how much I love Objective-C yet ?   very sweet.  Damn shame I will have to re-write all this game to be able to port it …