Game Design, Programming and running a one-man games business…

Year: 2010

Vertex Buffer Driver Hell

Posted on February 4, 2010

Some days as a programemr suck. Today is one such day.
All my old games use directx7, with my own engine,. Gratuitous Space Battles uses a new engine, directx9, and all is well.

In January this year, Kudos and Democracy stopped working for lots of people with the new nvidia drivers. They got crashes in the vertex buffer lock code. Obviously I hadn’t changed a thing. the games had worked fine on thousands of PC’s for years. Suddenly nvidia must have changed the way they handle vertex buffers under directx7. Thanks guys!

The old code was very old school and simple. I locked a vertex buffer, then copied in memory, then unlocked, and rendered from them. Big deal. I didn’t use any cleverness with the buffers gradually filling up and then discarding them. (I do that in GSB) I always locked the whole buffer and the lock flags always looked like this:

HRESULT hr = VertexBuffer->Lock(DDLOCK_WRITEONLY | DDLOCK_DISCARDCONTENTS | DDLOCK_SURFACEMEMORYPTR,
(VOID**)&BufferMem,&bufsize);

For every VB lock. I did a few of these each frame, mainly for rendering text. This may not be optimum, but it worked fine, all return codes checked ok on all cards and all drivers.

Suddenly, on my nvidia 8800 GTS, and for everyone else with new drivers (except the 9800 GT), this crashed, and would only work if changed to this:

HRESULT hr = VertexBuffer->Lock(DDLOCK_WAIT | DDLOCK_SURFACEMEMORYPTR,
(VOID**)&BufferMem,&bufsize);

In theory this is less efficient. But suddenly it works. Hurrah. Except not for 9088GT owners. I tried this:

HRESULT hr = VertexBuffer->Lock(DDLOCK_WAIT | DDLOCK_WRITEONLY | DDLOCK_SURFACEMEMORYPTR,
(VOID**)&BufferMem,&bufsize);

This also works on my 8800GTS, but even this does not work on the 9800GT. I can’t get a reply from nvidia, and the developer forums there hurl abuse and sarcasm at anyone who dares to ask about why a directx7 program won’t run (I’ve read a fair few threads there). Apparently we should all just STFU and re-code everything in DX10. Err right….
Anyway, I have nothing to say on this topic other than it depresses me. I don’t want to be fixing games I finished a few years ago, I want to work on new stuff…but obviously I need to support all my customers. I just wish someone at nvidia would tell me what they changed, and how to work around it for all their video cards. I emailed them a few days ago but got no reply…

If you work an nvidia, or know everything about directx7 VB usage with modern drivers, please shower me with your wisdom. And if you have an nvidia card, feel free to try the demo to Kudos 2 or Democracy 2. Both should now work, but I’d love to know if they don’t, what video card and driver you have…

bah :(

Best cruiser explosion ever

Posted on February 3, 2010

is at 2 minutes 32.

http://www.youtube.com/watch?v=_ZIPsXY7_fc

Thats what I’m aiming for. Obviously without ILM’s budget, but hey.

I’m tweaking  explosion effects right now. I’m waiting for one more expansion pack ship, then the turrets, and then I can start balancing them and doing the new missions. I’ll show some screenshots of the new stuff before I release it.

The format of this expansion/ DLC is very similar to the tribe. New race, with new weapons. Plus asteroid belts will look 3D in the new mission. yay.

Movie review? Enigma

Posted on February 2, 2010

Here is a film you may like if you are a bit geeky and haven’t seen it:

Enigma (2001)

http://www.imdb.com/title/tt0157583/

What is it?
A low key drama / love story about code breakers fighting to break the German enigma code during World War II

Who is in it?
Kate Winslet, Jeremy Northam, Tom Hollander, Matthew McFadyen, other people.

Quick Plot:
Tom Jericho is a code breaker based at Bletchley park, recalled to help break enigma again after the Germans mysteriously change the code mid-war. Interleaved with the code breakers attempts to break the code, is a love story between him and fellow Bletchley park worker Claire Rommelly, and a spy story based around a ‘mole’  feeding information to the Germans. There is little to zero action or spectacle. Only one bullet is fired as I recall. And the car chase may disappoint smokey and the bandit fans.

What’s Bad about it:
Some fairly cringeworthy romantic scenes and dialog. An annoyingly repetitive musical theme. A few fairly contrived and convenient plot devices. Some general purpose stereotyping of maths geeks.

What’s good about it:
It’s about the birth of computing AND fighting WW2. What’s not to like? Plus a great supporting cast, and a good script in places. Surprisingly historically accurate (glosses over alan turing though, presumably because they wanted a heterosexual love story). Also, it treats you like you are paying attention, and doesn’t break down the complexity of the core topic (encryption) to sub kindergarten levels like many Hollywood movies would.
The plot is complex enough to keep you guessing.

Best Scene:
Tom Jerichos explanation on how enigma works to the American General. This is the way all programmer should speak to their boss when asked that irritating question “How long will it take?”

Best Character:
Jeremy Northam was born to be the slimey, suspicious and sarcastic British Intelligence chief.

Best Quote:
“Given the circumstances, Miss Wallace, I think we might risk first names.”

Buy it or Rent it. It’s good :D

I’m working on both an expansion, and some UI improvements for Gratuitous Space Battles. I’ll blog on them when they are ready.

Deployment Interface Tweaks

Posted on February 1, 2010

The deployment UI for GSB is not as good as it could be. I’m aware of this, and more acutely aware of it, because this is the main meat and potatoes of the game itself. The battles are great fun, and look cool, but a player who really gets into the game will spend considerable time on the deployment screen. I was thinking recently (and a post by a player on the forums reminded me of it) that I should display to the player the ranges he is fiddling with when assigning shooting orders. I’ve ended up fixing four problems here.

Firstly I changed the wording from ‘max range’ to ‘Move to attack at this range’, which makes more sense. Weapons will always fire at targets the minute they enter range, these instructions are for movement, not firing, and tell the ship to move to range X to attack fighters, or Y to attack frigates, depending on the current target. This was not clear. (It’s still imperfect, but better).

Secondly, I wanted to display the range on the screen as you changed it, and decided to re-use the white range circles to do so, which was fine, albeit requiring me to fix all kinds of other minor quibbles. It meant that I should allow the player to drag that window aside so they can see whats going on ( a good idea anyway), leading to a few tooltip bugs I had to fix. Once I was staring at that window, it became clear that a lot of the weapons module strips on there were redundant. If you have 5 cruiser lasers, you only need a single entry for them, to allow you to check and auto-set their maximum range, so now it says cruiser laser (x5) rather than spamming that window.

Minor changes, but lots of minor changes make for a batter, less frustrating and more fun game. Who knows, it may double sales! (unlikely :D)

The fallacy of features. New and not improved.

Posted on January 30, 2010

I put up a new article, in more detail on how GSB was made and what was involved. You can read it here.

Recently, in between working on patch 1.31 and the mysterious second add-on for Gratuitous Space Battles, I’ve been looking at some technical issues people are suddenly having with Kudos 2, Democracy 2 and Some of my other games. Suddenly, without me patching or changing anything, people started complaining about vertex buffer crashes. At first, it seemed to be Windows 7, or Windows 64 related, at which point one naturally assumed that the geniuses at Microsoft have ballsed up yet another operating system, but then the odd vista or even XP user had similar issues. Then it suddenly clicks that new nvidia drivers were released, and everyone having crash problems had an nvidia card.

I use vertex buffers differently in GSB than I do in my other games. I was using them in a slightly unusual way before. A way that is perfectly legit, that directx says is fine, where the video card returns no error message and says its all fine, and working great. Everything is good in the world.

And then suddenly, a few weeks ago, with their new drivers, some brainiac at nvidia has obviously thought ‘sod it, who cares. If they don’t use a VB in the way WE at nvidia like to use it, who cares it it breaks?’. And thus bug-ridden drivers are released. I have absolutely no doubt that the latest trilinear bump-depth-shadow-pixelling demos in directx11 look just superl33t at GDC with the amazing nvidia code. Just a pity that they couldn’t be assed to check if all the older applications still run isn’t it? Especially given that the entire modular COM design of directx is specifically designed to ensure 100% backwards compatibility.

Nvidia are still in a cold-war mentality arms race where they think all people want are features. It’s the same as Microsoft. “Give them new features!” “Shiny things!”. When Vista came out it was promoetd on the basis of the new flip-view. Have you ever used it? Me neither. Fuck features. I don’t want features. My mobile phone doesn’t even have a camera on it. My home phone doesn’t have an answering machine on it. Features do not get my money. Reliability and Performance gets my money.

If Windows 7 was advertised purely as “Vista, but more reliable, and quicker”, I’d buy it today. When I buy a video card I only care about how compatible it is. The performance difference these days between equal priced cards is so small they even need to blow up screenshots and use arrows pointing at pixels which show the difference. Who cares?

Worst of all, this obsession with tomorrows new feature rather than yesterdays compatibility is putting two pressures on pc game developers like me:

#1 take time away from making new PC games to actually go back and re-code old ones to work around nvidias latest ideas.

#2 Seriously think long term about doing browser games or console games, where this isn’t such a problem.

I’d hate to have to do either :(