I liked Pierre’s The Prophet Programmer post. Go read it now.

Now of course that post is a rant. It exaggerates. It puts everything into one bit grayscale colors. There’s never one person completely like this “prophet programmer” and another like the idolized “best programmer… not afraid of anything!!1″.

But it does highlight at least this thing: some aspects of programmer’s behavior are either useful or not.

Obsessing over latest hypes, “the proper ways”, following books by the letter just by itself is not useful. Sure, sometimes a dash of “proper ways” or recommendations is good, but the benefits of doing that are really, really tiny. Hence it’s not worth thinking/arguing much about.

Here’s some actually useful programmer traits instead. I’m thinking about real actual people I’m working with here, even if I’m not telling names.

He feels what needs to be done to get the solution, in the big picture. Sometimes these are unusual ideas that probably no one is doing – because everyone has always been seeing the problem in the standard way. The solutions seem obvious once you see them, but require some sort of step function in thinking to get there. Zero iteration way of hooking up touchscreen device input to test the game is to play the game on PC, stream images into the device and stream inputs back. Least hassle free asset pipeline is when there is no “export/import asset” step. Or a more famous outside example, tablets before and after the iPad. You rarely, if ever, can do things like that by doing user surveys or improving on existing solutions; you need someone who can see through and find what’s the actual problem you want to solve. This guy is worth gold.

She can cut things. “Perfection is achieved, not when there is nothing more to add, but when there is nothing left to cut away”, quoth Saint-Exupéry. To be good at doing anything you (both you and your team) need to focus, which means cutting things. Let go of bad ideas and blind alleys. If your justification for doing it is “but we already spent so much time on it”, just don’t – it will only get worse. Cut features that aren’t quite ready by the deadlines. Remove old things that aren’t useful anymore. Doing that can and will make some people upset; it’s really, really hard to postpone or even completely abandon a thing that someone put a lot of effort into. But it needs to be done; and you need her on the team to make these hard decisions.

That other guy is freaking fast. And not in a sense of “types tons of code real fast and then sometimes it works, and two weeks after someone else has to clean it up”. No – he’s cranking out good, solid, tested, working code at incredible speeds. Got ten bugs; they are fixed by next day. Got a new feature to do; commits with everything implemented (and working!) are pushed in a few days. When he goes on vacation your burndown chart changes slope. How he does it? I don’t know. But by all means, keep onto him!

The other girl can figure out any complex problem real fast. Be it a tricky bug, unexpected behavior, really weird interaction with other systems – others could be spending hours, if not days, trying to figure out what’s going on. She, on the other hand, checks just a handful of things and goes “ha! the problem’s right there”. As if applying binary search to the whole problem space, except to everyone else the space seems unsorted and they don’t even know what they’re looking for!

This dude can keep a ton of context in his head while doing anything. How will this feature interact with dozens or even hundreds of other features; he’s able to think about all of them and majority of corner cases and get everything right in one go. Would take dozens of roundtrips between coding & QA for someone else to get right. When estimating effort for new things, he can immediately list all the tricky work that will need to be done; whereas others would go “sounds easy” only to find out it’s a month of work.

She’s not satisfied with the status quo. No this isn’t good enough, she says; and let me show you where & how spectacularly it breaks. And it does not matter if everyone else is doing it this way; here’s why putting that stuff into uniform grid isn’t good. A lot of times you need this extra bump to snap out of your own “this is good enough, no one will care” thoughts.

He’s doing a lot of boring work to get others more productive. There’s a ton of boring work on even the most exciting projects, and someone has to do it. He’s often the unsung hero, quietly working on infrastructure, build times, fixing annoyances in the tools, processes and workflows; all just so that others can be better at doing exciting things. You could call him a janitor or a plumber if you wish, but any place gets rotten and broken real fast without those people.

…and the list could go on. Unlike obsessing over irrelevant details, these make a difference. Makes your team run circles around others. Helps you solve hard problems, invent things, moves you forward at enormous velocity.

You need people with those traits and attitudes.

Almost four years ago I wrote how we test rendering code at Unity. Did it stand the test of time and more importantly, growing the company from less than 10 people to more than 100 people?

I’m happy to say it did! That’s it, move on to read the rest of the internets.

The earlier post was more focused on hardware compatibility area (differences between platforms, GPUs, driver versions, driver bugs and their workarounds etc.). In addition to that, we do regression tests on a bunch of actual Unity made games. All that is good and works, let’s talk about what tests the rendering team at Unity is using in the daily lives instead.

Graphics Feature & Regression Testing

In daily life of a graphics programmer, you care about two things related to testing:

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At work we switched to Mercurial almost two months ago. Like Richard says, it was time to stop using Subversion. Here are my impressions so far.

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You are writing some system where different implementations have to be used for different platforms. To keep things real, let’s say it’s a rendering system which we’ll call “GfxDevice” (based on a true story!). For example, on Windows there could be a Direct3D 9, Direct3D 11 or OpenGL implementations; on iOS/Android there could be OpenGL ES 1.1 & 2.0 ones and so on.

For sake of simplicity, let’s say our GfxDevice interface needs to do this (in real world it would need to do much more):

void SetShader (ShaderType type, ShaderID shader);
void SetTexture (int unit, TextureID texture);
void SetGeometry (VertexBufferID vb, IndexBufferID ib);
void Draw (PrimitiveType prim, int primCount);

How this can be done?

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I was recently optimizing some OpenGL ES 2.0 shaders for iOS/Android, and it was funny to see how performance tricks that were cool in 2001 are having their revenge again. Here’s a small example of starting with a normalmapped Blinn-Phong shader and optimizing it to run several times faster. Most of the clever stuff below was actually done by ReJ, props to him!

Here’s a small test I’ll be working on: just a single plane with albedo and normal map textures:

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During development of Unity 3.0, I was not-so-pleasantly surprised to see that our cross-compiled shaders run slow on iPhone 3Gs. And by “slow”, I mean SLOW; at the speeds of “stop the presses, we can not ship brand new OpenGL ES 2.0 support with THAT performance”.

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Realtime shader languages these days have settled down into two camps: HLSL (or Cg, which for all practical reasons is the same) and GLSL (or GLSL ES, which is sufficiently similar). HLSL/Cg is used by Direct3D and the big consoles (Xbox 360, PS3). GLSL/ES is used by OpenGL and pretty much all modern mobile platforms (iPhone, Android, …).

Since shaders are more or less “assets”, having two different languages to deal with is not very nice. What, I’m supposed to write my shader twice just to support both (for example) D3D and iPad? You would think in 2010, almost a decade since high level realtime shader languages have appeared, this problem would be solved… but it isn’t!

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Just spent half a day debugging this, so here it is for the future reference of the internets.

In a deferred rendering setup (see Game Angst for a good discussion of deferred shading & lighting), lights are applied using data from screen-space buffers. Position, normal and other things are reconstructed from buffers and lighting is computed “in screen space”.

Because each light is applied to a portion of the screen, the pixels it computes can belong to different objects. If in any place of lighting computation you use textures with mipmaps, be careful. Most common use for mipmapped light textures is light “cookies” (aka Gobo).

Let’s say we have a very simple scene with a spot light: (more…)

Almost half a year ago I was wondering how to implement T&L in vertex shaders.

Well, finally I implemented it for upcoming Unity 2.6. I wrote some sort of a technical report here.

In short, I’m combining assembly fragments and doing simple temporary register allocation, which seems to work quite well. Performance is very similar to using fixed function (I know it’s implemented as vertex shaders internally by the runtime/driver) on several different cards I tried (Radeon HD 3xxx, GeForce 8xxx, Intel GMA 950).

What was unexpected: the most complex piece is not the vertex lighting! Most complexity is in how to route/generate texture coordinates and transform them. Huge combination explosion there.

Otherwise – I like! Here’s a link to the article again.

It’s funny how one’s view on things change over time.

Back in 2002, I wrote something that would be roughly translated like “C++ amazes me more and more”. In a positive sense! And I was talking about what is Boost.Spirit now.

A reply on local game development forums I wrote today (again, rough translation): “C++ is very hard and quite a horrible language, maybe you should not use it unless there are no alternatives”.

That’s quite a change in attitude we have here!

I feel like much of C++ horrors are a consequence of “it just somehow happened” (the whole template metaprogramming thing) or as a backwards compatibility with C requirement. Or maybe not, but I do agree with what ryg says here. Let’s play the internet memes: