Archive for the 'Bullet3d' Category

Zurp 1.0 Postmortem

December 15th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

Last September I wrote a blog post introducing Invader Zurp which revealed a little of the back story on how I came upon this new game idea after it’s first 2 months in development. Fast forward to 3 months later and Invader Zurp had just hit the App Store! I thought it would be useful to sit down and review the last 5 months of development, kind of plan out where I want to go from here and go over the events and insights that I thought were most influential during development.

The Story So Far…

So to recap the original blog post a bit, it was the middle of the summer (2011) and I had been working my brains out on Cannonade for the previous 6 months. I was a little discouraged at that point because progress wasn’t coming quite as quickly as I had hoped. Reception from my testers (just friends and family at that point) hadn’t been as positive as I had wanted either. I still had a very clear vision of what I wanted Cannonade to be and still believed that there is a ton of untapped potential for multiplayer-only games on iOS. But there was only so much I that could do as a one-man team and testing a multiplayer game can be quite time consuming. I took the family on vacation in early July and was able to step away from things for a while. It was then that I got an idea for a single player experience that distilled the core gameplay mechanic of Cannonade down to it’s essence. Thus Invader Zurp was born. Within two weeks I had modularized the Cannonade game engine, re-written the graphics sub-system in OpenGL ES 2.0 and had a working prototype. And it was fun! I found myself on very long “testing” sessions playing even after I had verified my fixes. I seeded the first alpha version in early September and wrote the introductory blog post. Then began the journey of finishing the game and kicking the darn thing out the door. (more…)

Invader Zurp is on the App Store!

December 15th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

Aright it’s here! Invader Zurp, the project I have worked so hard on for the last 5 months is now for sale on the App Store! I want to thank all my wonderful testers for all their time they put into playing it and even more for the thoughtful and productive feedback that they so lavishly furnished on me. I couldn’t have done it without you!

Check out the gameplay trailer here:

Now Go Get It!

Application-Specific Bullet Physics Optimization

December 13th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

In developing Cannonade and Invader Zurp I have invested a fair amount of time becoming familiar with the Bullet Physics Library and trying to milk every bit of performance out of it as I can. Realistic physics simulation plays a crucial part in both games and is also the performance bottleneck in the majority of gameplay scenarios with both. When trying to optimize for performance I generally see myself using two kinds of approaches. One is a higher level algorithmic approach that tries to see ways to create less work or avoid work in order to keep things going fast. Once I have nailed down as best I can, the minimum set of work that I really cannot avoid doing, then comes the work of getting down and dirty and speeding up the routines that actually do that work. When I initially approached the problem of speeding up Bullet, I first simply treated it as a black box (work that I wouldn’t be able to avoid) and explored what kinds of compiler configurations I could leverage to create the fastest possible execution of the physics simulation work. Later, after I had nailed down the gameplay mechanic for Invader Zurp I was able to start specifically attacking the set of physics simulation work needed for the game and whittled it down to a much smaller amount using some simplifications, accuracy compromises and psychology.

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Invader Zurp Progress

October 27th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

Above is some footage from the current Invader Zurp alpha (apologies for the bad exposure). As you can see, things have come quite a ways since I released the first video! There are a lot more visual effects, 5 music tracks from Monte ‘Trance’ Emerson, a new gameplay mechanic, an in-game currency system and tons of other little advancements. I must say that I feel like things are progressing quite nicely! I still have a ways to go though and so I am going to continue cranking away with my head down until it is finished.

What are your thoughts on how development is going? Let me know in the comments. Also, a huge thank you to all of my testers who have given me invaluable feedback on all the builds thus far.

Invader Zurp

September 12th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

So for those of you on my Cannonade TestFlight profile, you might have noticed that I havn’t seeded a build for about two months. I have a good explanation for this.

Lets rewind back to right after my last Cannonade seed build. I was on vacation at the time and had the opportunity to stand back from Cannonade and evaluate things from a different perspective. Sometimes I don’t think I seek out those opportunities to just sit and think as much as I should (just thinking sometimes makes me feel a bit lazy for not doing). At one family gathering I observed my older son playing Fruit Ninja on his aunt’s iPhone. I was aware of Fruit Ninja and knew that it was a definite App Store success. As I watched him play I thought to myself “That just one play mechanic. One. Repeated, millions of times over and over and over.” This is the typical MO of most games that are successful on the App Store. Simple, easy to pick up and well implemented with good production values. With Cannonade I am trying to break new ground on the App Store. I still believe that there could be a place for deep multi-player experiences on the App Store and I think that Cannonade is on the right track. But watching Fruit Ninja got me thinking. Did I have a single, fun gameplay mechanic that I could repeat millions of times? The core fun mechanic of Cannonade is “Knock Your Friend’s Castles Down.” Maybe I could modify that to just “Knock Castles Down.” Even knocking down dumb castles was fun in and of itself. Maybe I could repeat that experience millions of times and put out a more limitedly scoped single player experience? I decided that it would be a really fun exercise and that I would put Cannonade on hold for a few months while I brought this new single player game to market. I call it “Invader Zurp“.

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iPod Touch Server

June 11th, 2011
Spencer Nielsen Follow snielsen42 on Twitter


Top-down view of the Aoren Software datacenter in the living room corner.

Why, you might ask? In my case the answer is simply because it is my only alternative. In development of my game Cannonade there quickly arose a need to be able to replay my user’s completed games and validate the results with exactness. In order to obtain that level of exactness, my games must execute with complete determinism. Unfortunately the implementation of floating-point match according to IEEE754 can actually vary somewhat between x86 and ARM processors. This means that if I replayed a game that two of my users played using iOS devices on an x86-based server, the results of the replay would very quickly diverge. Thus I am left with no choice but to set up a dedicated iOS device to wait for notifications of the matches that it needs to replay and validate (a process I call judging). An iOS server you might say.

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When Bullets Move Too Fast…

June 1st, 2011
Spencer Nielsen Follow snielsen42 on Twitter

Did you know that bullets (and other quick moving objects) in video games sometimes exhibit magical properties if they move too fast? If they gain enough speed, sometimes they can even pass completely through other objects without leaving a scratch or affecting them at all! You might have seen this happen occasionally in games that have a lot of complicated physics simulation. Sometimes fast moving objects just seem to pass through the ground or other objects. Unfortunately this is not a desirable user experience and it quickly breaks the illusion the game is trying to convey. This phenomenon is called “tunneling” and game developers attempt to deal with it in a variety of different ways. I thought I would share my unique combination of techniques to deal with it that I used in Cannonade. I have not seen this specific combination of techniques explained or suggested anywhere and so I thought it might be beneficial to share what I have learned with others who might also be suffering from object tunneling woes. First lets explain how most modern game physics simulation works and investigate why this problem crops up.

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Cannonade 0.5.8 is now seeded

May 9th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

The focus of this update is the new in-game tutorial! Now when you first launch Cannonade if you have never run through the tutorial it will prompt you to do so. The tutorial level is meant to teach new players how to use the battle interface and get them some target practice with the fundamentals. Give it a whirl and let me know what you think!

Complete Changelist:

  • Bumped engineCompatibility to 0.5.8. (this means all games previously created by versions <= 0.5.7 will be deleted)
  • Initial implementation of the tutorial game type and level.
  • Made some menu refinements and added a “Wiki/File A Bug” menu option.
  • Made it so that you are prompted to run through the tutorial if you havn’t before on that device.
  • A few quick menu sound effects.
  • Added detailed statistics gathering.
  • Fixed lots of little simulation execution bugs.
  • Tons of leak hunting.
  • Added friends info to the game server packets and cleaned up the server code a bit.

Alpha Testing List

Would you like to be one of the awesome alpha testers that help make Cannonade great? Send an email to: [email protected] and I will reply with instructions on how to get onto the Trac server, Testflight list and tester forums.

Cannonade 0.5.7 is now seeded

April 25th, 2011
Spencer Nielsen Follow snielsen42 on Twitter

The two most note worthy changes in this build are SPEED and WEAPONS! After spending two days on physics performance optimization and a week and a half on graphics performance optimization Cannonade now runs a lot faster on both the iPhone and the iPad! There are still speed gains to be had but the framerate difference is like night and day. Thanks to your voting, in this build we also have the debut of the Gravity Bomb, Fire Bomb and Friction Bomb weapons. They still need to be tweaked and balanced but they are still fun to play with. Give them a shot!

Complete Changelist:

  • Bumped engineCompatibility to 0.5.7. (this means all games previously created by versions <= 0.5.6 will be deleted)
  • Did a lot more investigation into physics performance. Content with how much I have for now.
  • A HUGE graphics performance related commit.
  • Added the Gravity Bomb, Fire Bomb and Friction Bomb weapons.
  • Added powerSlider tuning buttons
  • Added a block override fade timer
  • Added all sorts of neat effects to the gravity, fire and friction bombs.
  • Added a new lava island level to design around the !FOGENABLED and NONBLENDEDLAVA speedups.
  • Initial “connection-less” Game Center implementation. Initial support for key-based communication (added libcrypto.a)
  • Added a label toggle button in game and removed the reticle label fade.
  • Reworked the visual styling of the shootMenu.
  • Abandoned scrolling on weaponScrollView because UIScrollView is too buggy.
  • Added BlockAttachements.
  • Added CANNON_IMPACT and BLOCK_POOF emitter types.
  • Tweaked Gravity Bomb effects.
  • Removed old levels.
  • Fixed a bug where resetCollisionFilters was not being called (killed replay).
  • Extended ASGlassButton to handle corners.
  • Fixed some ASGlassButton issues that were causing uneccessary redraw.
  • Added a biased decal shape as a hack until http://aorensoftware.dyndns.org:8000/TRAC/ticket/145 gets fixed.
  • Refined convex sweep tunnel protection even further.
  • Added convex sweep querying to block movements as well.
  • Added LOCALMODELVIEW so that we don’t stall OpenGL everytime we need to read/update the camera matrix.
  • Added more benchmarking oriented functionality and updated libbullet.a.
  • Tweaked build settings and switched compilers to llvm-gcc4.2.
  • Fixed the editor back into working shape.
  • Fixed cull and texture state for projectiles until they get their real objects.
  • Fixed big in terrain removal code that was smashing memory.
  • Fixed some block label override bugs.
  • Fixed key loading.
  • Fixed projectile state dirtying.
  • Added an in-game fps counter.
  • Added server games auditing to the ADMIN_MENU.
  • Checks first before copying into history now.
  • Misc bug fixes.

Alpha Testing List

Would you like to be one of the awesome alpha testers that help make Cannonade great? Send an email to: [email protected] and I will reply with instructions on how to get onto the Trac server, Testflight list and tester forums.

OpenGL Game Optimization for iOS

April 22nd, 2011
Spencer Nielsen Follow snielsen42 on Twitter

For the past month or two I have been lightly seeding to Cannonade to testers. I have gotten the strong impression that the “fun” of my game was unfortunately getting lost in the low framerate. There is a certain reaction in the human brain that I am trying to evoke by making the blocks explode and collapse in physically realistic ways. However, when the framerate is too low the perception of motion is lost and so is my core game mechanic. I first spent a lot of time optimizing the execution of the Bullet physics engine and found a significant speed increase by tweaking compiler settings. I found that the execution of the physics simulation on iOS devices was very strongly locked to CPU performance. Now the time had come to start attacking the performance of the graphics engine. I was hopeful that I would be able to find even more significant speedups in this area because the graphics engine was custom written by myself and I could also employ device specific optimizations to take advantage of specific strengths or avoid specific weaknesses. Many of the techniques I tried out were nothing that hasn’t already been done before but I thought it would be worthwhile to document my experiences executing them in my specific situation. These are the results of a week and a half of aggressive performance benchmarking, exploration and experimentation. It goes without saying that my results are very data set specific and so they could perform better, worse or the same when applied to a different iOS app.

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