Coder Corner

Here’s a quick test for adding a gravity gun to KP.

- run the exe

- select “Developer => Load test level => GravityGunTest” (the only level included in this release anyway)

- pick up the gravity gun in front of you when the game starts. The console in your back gives some additional instructions.

Very quick test put together in one week-end, there are some bugs, etc. Just to have something to post… not much time for anything those days.

I hate you. I truly, terminally, passionately hate you. You’re a fucking piece of insane, mind-boggling junk. Having used computers for more than 2 decades now, I can assure you that you are, without a shred of a doubt, the crappiest, lamest machine I have ever used. It makes me sad that you’re the one who survived, because you obviously deserve it the least.

And now for the question of the day:

• I bought a brand new USB memory stick. Looks great.
• I have been using it for less than a month, sharing files between 2 machines (Win2K, WinXP).
• And today out of the blue, I’m told that the stick is “write protected”. I can’t add files to it. I can’t remove files from it. I can’t even reformat the sucker. Google tells me that this is a common problem (!!) but none of the “solutions” I found online worked.
• Help? Anybody knows how to unlock that thing?

For all I can see, it looks like I wasted my money on one more piece of PC garbage, and I can just throw it away and buy another. This is fucking ridiculous. It makes my blood boil that this so-called “user friendly” PC is in fact a fucking clueless money-making bastard that couldn’t care less about users. If you would care about users you would allow me to install VC9 on Win2K, for a start!

My girlfriend broke her foot a few days after moving back to Zürich, just when we didn’t have a Krankenkasse. Thank you Murphy.

My Xbox died halfway through Wet. I suppose that game was too hot, since I got 2 red lights in the Red Ring Of Death. Overheating. I guess that is a noble death for a console. At least its life was useful. Maybe it will cool down enough to start again, after a while. In the meantime I used this as an excuse to buy one of the new slim PS3’s. Finished Uncharted 2, went halfway through MGS4, just started Ninja Gaiden Sigma. Now you know why there’s no time for updating that blog

Worked on a serialization framework for the PhysX SDK, something similar to this.

Started investigating “CSG debris” in my spare time. So you carve bullet holes in meshes via a CSG operation, generating debris pieces at the same time. Debris are then rigid bodies, etc. Currently playing with t-junction removals, retriangulations, all that fun stuff. The even funnier stuff will be to update all the PhysX mesh data structures after a CSG operation. Stan Melax has a brilliant demo with runtime CSG a while back, I guess that’s the inspiration for this small side project. I hope I’ll be able to include that in Konoko Payne if it all works as planned.

…and there’s probably a million things more to post, but I don’t have time…

In Ninja Blade on 360. No ninja coders there… But man, try to beat that score!!

The boss at the end of the Spain level was long and tedious, but I finished him. It’s a bit disappointing to see that the game re-uses the Switzerland level a second time, it feels a bit cheap. Lazy artists! But hey, this time I collected enough money to buy new weapons so it will probably be easier. I wonder if they unlocked some items like their garbage bins nearby the Technopark (*).

I am packing my PC tomorrow, and the relocation people pick the boxes up the next day. After that, I will be without a PC until I find a new flat in Zürich. It might take a while, so don’t expect a lot of updates for a month or so.

brb!

(*) completely private joke here

Here is another Konoko Payne release. The last one before moving back to Switzerland! The main change is that pathfinding is now performed via the Recast & Detour library. It’s just the initial implementation, so you may expect some troubles.

Changelist:

• added achievement stack, to make sure 2 achievements can happen at the same time
• added “friendly fire” achievement (make a sniper kill a NPC)
• “devil kick” achievement now unlocked when performed on 3 enemies
• disabled target lock on thrown characters
• Barabas: “stronger & stronger” sound is now interrupted if Barabas gets thrown
• it should now be possible to select the arrow keys for motion
• removed a lot of duplicate textures on characters
• disabled raycasts on invisible “cubes” around characters
• added trail on “COMCOMPunchHeavy” anim
• used new textures from Severed (there’s an option in the menu)
• the BV when in crouch but with a firearm should be a bit bigger, to avoid going completely through barriers => we now automatically switch off the weapon
• some transitions are now banned when in “locked crouch”, e.g. inside a ventilation duct
• added support for “multiple surface sounds” per texture
• added “ONI” sprites with shadows on title page
• weapon is now dropped from correct height in crouch mode
• added “dash” à la ONI
• implemented Skybox culling
• “steady cam” is now the default/preferred camera model
• the jumping gravity should look more like ONI’s now
• fixed camera rots for NPCs in jump anims
• fixed crash when selecting “End game”
• added ESC menu
• fixed bug when enabling inventory while there’s an impending intercom
• walljump is now possible a tiny bit longer against a wall
• added “land hard” anim for side wall jumps
• if killed while platform sound is on, it doesn’t stop when restarting from checkpoint <== should now be fixed
• optimized file loading (binary state machine files, music streaming, better file management, etc)
• some attacks from Elite Striker should have a fixed rotation => done
• running and jumping constantly should work better now
• added message from Shinatama when helipad platform goes down
• added two new combos
• there is now an option to disable “attack buffering”
• switched from PathEngine to Recast. The prototype and the game level should now have better navigation meshes. On the other hand pathfinding against dynamic obstacles may not work anymore.

Some time ago I mentioned the ICE kernel and somebody asked me about the source code. Well sorry, I’m not going to release this just yet. It’s not secret or anything, it’s just extremely ugly-looking source code. You have to realize: this is the first part of the engine I wrote, somewhere around 2000. I won’t release this without a serious cleaning / refactoring pass first.

However I can briefly describe what it does. It’s nothing special, really. To be perfectly honest I was just experimenting with random ideas, to see if they would work, etc. I never imagined I would still be using this stuff almost 10 years later. Also, even if I’m still using this at home, it doesn’t mean I would ever want to replicate this in a “real” engine at work, or on a console.

So anyway it all started as a reaction to the vanilla reference counting that we’d been using before, in “Irion“. In that engine we had manual, explicit “IncRef” and “DecRef” calls. You couldn’t delete an object directly (private dtor), instead you DecRef, and if the counter reaches 0 the object deletes itself. Standard stuff. But we had a lot of issues with that, people forgot to call “IncRef” or “DecRef”, unused objects that should have been deleted were found in memory alive and well, or quite simply we got many crashes from dangling pointers. Typical BS.

After the death of Irion I started my engine from scratch at home, and I really didn’t want to end up with the same mess (*). So I was looking for a solution to this, that’s the context. At the time the information about engine architecture on the Internet was scarce, or maybe I didn’t look well enough, in any case I don’t remember finding anything very useful online. So I started to build something, probably more out of boredom and curiosity than necessity.

First of all, it only works for objects inheriting a base class. For historical reasons, this base class is called “Cell” (why this is so is another, completely different story). Cell objects register themselves to the “kernel” in their ctor. They unregister themselves from the kernel in their dtor. The kernel is a singleton, for better or for worse (it was almost 10 years ago, I didn’t care about multiple threads).

Now when you create a “reference”, you still have an explicit function to call: “AddRef”. As the same suggests, it does not increase a simple reference counter (as “IncRef” was doing), it keeps track of the “owning object”, or simply owner, and the “referenced object”, or simply reference. Those couples of (owner, reference) are stored inside the kernel, in something called “reference tracker”.

If there is any intelligence in the system, it might be in the reference tracker. This is a somewhat creative data structure designed to keep track of those pairs efficiently, both in terms of speed and memory. A  (owner, reference) pair is simply a DWORD, made of two 16-bit IDs. The number of objects is limited to 64K, yes. The pairs are simply stored in a contiguous amount of memory, like a vector of DWORDs. Given an input Cell, the structure otherwise provides O(1) access to:

• its number of owners, and the set of owners
• its number of references, and the set of references

So, in a standard system you would get a Cell object and you could only do something like “GetRefCount”. It would return “3″, and you would know that this Cell is referenced by 3 other Cells somewhere. In ICE, you can easily ask for the “ref counter” (= the number of owners), but also who the owners are. That’s the first building block.

The second step is to investigate what happens when you actually delete an object. As we saw before, on deletion a Cell unregisters itself from the Kernel. The Kernel in turns tells the Reference Tracker about this deleted Cell. And since the Reference tracker knows what other Cells are still referencing the deleted one, well, from this point it’s easy to call the owners for notification. That function is called “OnInvalidReference”, IIRC.

So, for example:

• you have a Material, 3DS-MAX style
• it has a Reference to a Diffuse texture
• if you delete the texture (and I mean really, a savage “delete ptr” anywhere), the system calls Material::OnInvalidReference(), with the deleted Cell (the texture) as a parameter. From here, the Material can fix its dangling pointer (at least it was the original idea, but it evolved a lot afterwards)

There are a bunch of technical issues here with circular references and how to implement all this efficiently, but those are details “beyond the scope of the discussion”. The question was about containers, remember? Well it should be obvious what the next part was: of course I made a Cell-based container. Completely customized object, STL-Vector-style, that can hold Cell pointers, nothing else. The benefit, as you already guessed from the previous post and previous paragraph, is that if I ever carelessly delete a Cell object stored anywhere else in one of those containers, the kernel will know, it will call the container’s “OnInvalidReference”, and the container will remove the bad pointer from itself, automatically. Done!

This, unfortunately, was only the beginning of my weird architecture experiments.

Not long after that, I tried to fix the other main pain in the butt that had plagued Irion since the beginning: serialization. Oh man how I hated writing serialization code in Irion. In ICE, I really wanted to have an automatic mechanism to do that for me. IIRC the idea came from the Half-Life SDK: they had this great “offset of” macro that would give the offset of a member within a class. It’s pretty standard and well-known those days, but at the time, and for me, it was a mini revolution. The serialization code in Irion had to be written manually and painfully. Thanks to this single macro, suddenly it was possible to automate a large part of it. I’ll spare you the details as I’m sure you’re all aware of this stuff now, it’s used and over-used for serialization, meta-data, scripting, etc. The point to take home here is that the kernel suddenly knew about Cell classes’ members… and in particular, about other Cell pointers stored within Cell classes. Which opened a whole brand new Pandora’s box.

Remember, I was only toying at home. This was not production stuff. The ICE engine has never been used commercially or anything. No harm done.

Let’s face it: what’s the point of calling “OnInvalidReference” for a given Cell to clean its dangling pointers… if you can do it yourself? “If you want something done correctly, do it yourself”. Right. So that’s basically what I did. Provided you declared members with the correct serialization macros, the kernel does not call objects anymore to tell them to clean an invalid pointer. The kernel cleans the invalid pointer all by itself. It knows where it is! So it just clears it. Zero it. Nullify it.

That’s usually the point where type-safety zealots and other fans of “clean C++” (talk about an oxymoron) give up and start throwing rotten tomatoes at my indecent lack of concern for “proper OO ways”. (But then again, if “Boost” is the “proper” infant of the OO way, I’ll more than gladly remain a non-believing maverick. Boost! What a joke!)

But wait! I’m not done! I still have to tell you how discovering handle-based “weak pointers” changed the picture over again! And how the kernel can “remap” itself and move objects in memory under the hood to reduce fragmentation!

Come back! It’s fun!

Hello …?

(*) I failed

While doing backups I found this picture of Araña, one of the characters in “Wanted - weapons of fate“. It has a special meaning for me. I see it both as a proof that the Barcelona office did have talented artists, and that “the management” (or whoever was behind the important decisions, it was never all that clear) was just living on another planet.

To me this is one of the most, if not the most awesome render ever created by our artists during the whole project. I think it is very obvious why it has potential. Why it would be a good idea to polish this secondary character, and give it some more screen time. Why it would draw hordes of nerds to the game. Why it would please all the fans (what do you mean you did not expect them to be disappointed when discovering that Angelina is not in the game?!). At the very least, if nothing else, put it somewhere on the box. Create posters. Send it to IGN and Gamespot, I don’t know. Something.

Instead… well, did you see that picture anywhere? Exactly my point.

They saved it for a mindbogglingly weird promotional stunt in a male magazine that should remain nameless. Of all the crappy decisions made during this project, this one has to take the cake. As if the readers of [Censored] were interested in buying video games !? I don’t know, maybe they got lifetime subscriptions out of that deal or something.

Damn it, this one still makes my blood boil!

Played a bit more with Recast. It rocks so far.

I wonder if I could use the Recast nav-mesh with PathEngine?? Sounds like best of both worlds if Detour has some limitations. For example I don’t know yet if it handles dynamic obstacles very well.

The world is cut into several regions connected by portals. I think I will end up generating one nav-mesh per region. Then if a pathfinding query goes from point Pa in region Ra to point Pb in region Pb, I can always split the query into several sub-queries: first from Pa to the portal connecting Ra and Rb, then from the portal to Pb. Or maybe Recast’s “tiled” mode can do the trick directly.

Not sure how to handle moving platforms yet.

That’s what happens when you try to make ice cubes with sparkling water…

EDIT: wonder what happens if I try sparkling water in the coffee machine… too bad it’s already packed