Frictional Games Blog

Moved to the forums

jens — Tue, 12 Feb 2008 04:33:11 -0500

We have started a Work Log in the forum instead of using this blog. That way you can comment and discuss the contents with us!

Second video diary

jens — Mon, 15 Jan 2007 06:38:37 -0500

As promised we have created another video diary, this time demonstrating the enemies interaction with the player and the environment.

You can find download links in the media section on the official Penumbra: Overture website or use any of these to view directly in the browser.

GameTrailers.com, YouTube.com, video.Google.com

Physics blog

jens — Sat, 13 Jan 2007 09:20:32 -0500

Released a while ago but still a blog entry of sorts. Thomas takes you through some of the basics of what the physics in Penumbra: Overture are capable of.

You can see the video over at GameTrailers.com or choose any of the download options found on the official Penumbra: Overture site.

Next week we will post a new video where Thomas talks about the interaction with the monsters in the game.

A four spot developers diary

jens — Thu, 07 Dec 2006 06:49:55 -0500

Our blog will take a vacation to GamesXtreme.net for a while. We are going to write a four part developers diary over there and the first one is available now.

This first entry gives an introduction to Penumbra and how the project came to be.

Audio physics in Penumbra

jens — Thu, 21 Sep 2006 18:15:02 -0400

As much as the physics in Penumbra are for visual pleasure and for innovating interaction, the physics also come with a quite advanced and dynamic sound engine. In this blog I'll try and give a quick overview of what the physics sound engine can do! For this I have created a small video that you can download from mirrors on gametrailers.com, youtube.com and video.google.com The video is divided into several parts clearly marked with a number, following will be the narrative for each part.
1. All physical objects in the HPL engine(The core of Penumbra) can create a variety of sounds: Impacts, scrape and rolling sounds. How much detail you want to give an object is entirely up to you as the creator. In this first example I demonstrate a simple wooden box that uses 1 single sound to produce impact sounds. The sound is played at varying volumes depending on the speed of the impact. This is as basic as you can make it.
2. In the second part I drop the box on a surface, the surface is also producing a sound. The engine mixes them together making it sound like a mix between wood and dirt. This means that all materials sound different in the HPL engine depending on what material they interact with.
3. Using only one sound for an object creates quite a repetitive sound. That's why the sound engine is so dynamic, it's a simple task adding multiple sounds to an object and making the game randomly select a sound to play. To give even greater detail you can divide the sound into sub-groups that are triggered depending on the speed. For Penumbra we use 3 different groups with 3 sounds in each: slow, medium and fast impact speeds. In this clip I bounce twice with the box using the 33 sound details. The engine can support as many groups and sounds as you like, making the detail level extraordinary. But to keep the requirements down on the RAM/CPU/Time to create the sounds, the 33 system we chosen is quite adequate.
4. In this part I throw the box around on the dirt, both containing sound pools of 3*3. Making the sound picture quite varied and dynamic as the wooden boxes creates sounds in combination with the dirt.
5. For scrape and rolling sounds we only use 1 sound, this is a choice to keep the requirements down. We could use several sounds and the engine would randomly choose one of them, but we also do other nifty things with the sounds here making variations to a single sound. As the creator you can set several properties that will simulate real-physics scrape sounds. The engine will pitch and fade the sound depending on the settings you make. In this clip I simply push a large wooden box forward, making it produce the scrape sound, if you listen closely you can hear a subtle pitch as the movement speed changes.
6. As with the impact sounds, scrape and roll sounds for different materials are mixed together. Here I move the wooden box over several different materials, producing unique mixed sounds for each. I also do the same with a "glass box" to demonstrate a different surface type.
And there you have a short concentrated review of what you can do sound-wise with the physics engine. You can do everything from having one sound for all objects in the whole world, to having multiple unique sounds for every object in the world, making them entirely unique as they interact with each other. The only limit is how far you want to push the RAM requirements! Discuss this article in the forum.

The Fog Blog

thomas — Sun, 20 Aug 2006 09:31:23 -0400

Recently I sat down and added some simple fog. Fog can be really effective to simulate things like snowstorms, mist and fog (duh). Check out this moody photo for example:

[inline:3]

Back in the old days you could just set up some rendering parameters to get fog going, but now when you use fancy shader stuff it is not really that simple. When using a shader you override the standard rendering parameters and need to take care of all the stuff (like fog) yourself, so that is what I needed to do.

First up I needed to know what crazy formulas to use for the fog. It turned there wasn't much to it, just this little fellow:

fog = (end - z) / (end - start)

(Note: This is the linear fog equations, there are exponential ones as well, not going to go into them now though)

start
where the fog start
end
where the fog is at full amount
z
depth of the pixel from the viewer

This equation will give a value that works something like this:

fog > 1
No fog. When rendering we clamp the value to 1.
1 < fog > 0
Fog is semi visible
fog > 0
Fog is at full amount. When rendering we clamp the value to 0.

Now I knew all there where to fog equations and wanted to get it into the engine. First up I had to figure out when to apply this fog; should the objects be fogged while doing lighting, after lighting is done or perhaps before? I decided on doing it after all lighting was done, what way the fog rendering will be really simple and simply be drawn on top of all graphics all ready rendered. This is done like this:

Go through all solid objects and for each do:

Set up all needed shaders with the fog equation so the object is fogged correctly.

Blend the fogged object with the all ready rendered background, the lower fog value the more of the fog is visible.

That doesn't sound too hard, right? Now it only needs to be figured out how what kinda shaders to set up before rendering fogged object. I bumped into some problems now though, since older cards needed to be supported and no pixel shaders could be use. This means all the equation magic must be done in a vertex shader which leads us to the problem. Fog is a per pixel operation and vertex shaders can only do per pixel things if the equation is linear, which the fog equation is not. Let me explain:

The vertex shader looks something like is:

fog = (end - z) / (end - start)
IF fog < 0 fog = 0
IF fog > 1 fog = 1

Lets say a wall start at z=2 and stops at z=10. Now lets say that the fog starts out at 5 and ends 8. What you want the wall to look like is this:

[inline:1]

but instead I would get

[inline:2]

This has to do with the clamping explained above and meant I could not clamp the value in the vertex shader. Bummer, how should this be solved? This is when I remember good old texture look-ups. The problem can be easily solved by returning the fog from the vertex shader as a 1D texture coordinate (that is, a texture without height). Now I just set the texture to clamp it's coordinate between 0 and 1, clamping solved! Last thing that needs to be done is to let the textures have one colour channel and have the value smoothly go from 0 at coordinate 0 to 1 at coordinate 1. Now we got the fogging going!

But wait, there is more. What to do with transparent objects? The problem with this is that they are rendered after all the lighting and will not be affected by the current fogging. Bugger, I could not let transparent things stay sharp as the environment faded into the fog colour. Something needs to be done while rendering the transparent objects. The solution I came up with was to simply fade out the transparent objects depending on how deep into the fog it was. This can be done by using the same vertex shader and fog texture as before. There are more problems however.

The engine uses 4 different kinds of transparent materials and only two of these I knew how to fade. Transparent materials used are the following:

Additive texture + background
Alpha texture * texture_alpha + background * (1-texture_alpha)
Modulative texture * background
ModulativeX2 texture * background * 2

The two first are pretty easy to fade, the modulative ones a bit harder though. To make it easier to figure out what to do I set up what colour I needed the texture to be in, in order for the object to not show up. This is what I came up with:

Additive r,g,b = 0
Alpha alpha = 0
Modulative r,g,b = 1
ModulativeX2 r,g,b = 0.5

And after even more thought this is the equations I came up with in order to fade it all out:

Modulative Src * texture + (1-texture)
Additive Src * texture
Alpha Src.a * texture.a
ModulativeX2 Src * texture + 0.5f * (1-texture)

Src = texture of material
texture = fog texture

Wohoo, fogging is done for all things and that is without using any pixel shaders. The screenshot below shows how it looks ingame.

[inline:4]

Hope you enjoyed the fog blog!

More play

anton — Sun, 02 Jul 2006 19:03:14 -0400

Well, Its very tempting to write even more about the particle editor because I just cant get my hand of it, but I will spare you that reading :-)

Today I was supposed to play around with the light effects, but as I started to model a "dummy object" to test some theories on, I decided to do a character to practice some speedmodelling and also to see if Zbrush automatic Uv map system would be good. I ended up a couple of hours later with some kind of mortal combatstyleish character. I still think the pelt mapping method seems to be the best way of you want to do normalmapped stuff. The reason is that you want to get rid of as many Uv seams as possible to make the light more smoothly over your character and actually make the normalmap take care of the most shadows..thats at least my theory.

However, I ended up with a level, with one of my huge thundercloud partilcle systems and this nice looking character (not). Have a peak :-p

[inline:SceneViewer 2006-07-03 00-50-46-04.jpg]
[inline:SceneViewer 2006-07-03 00-49-41-18.jpg]
[inline:SceneViewer 2006-07-03 00-50-43-03.jpg]

More particles!

jens — Fri, 30 Jun 2006 14:56:42 -0400

[inline:1]Particles are so much fun that I need to talk about them as well! I blame the editor that we have, it's so fun to use that it's hard to not play around with it.

Today I was writing the tutorial on how to use the editor, then I got a little idea on how to show just how dynamic this editor is. So I created a "fun" particle effect using only 1 texture but with a quite fun end result.

You can watch the video at gametrailers.com.

For those that are interested I have also attached the particle file itself so that you can explore how it's created in the editor. Download [inline:2]

Particle mania

anton — Fri, 30 Jun 2006 14:42:36 -0400

So today I started playing around with the new particle tool. First of all, as usual when I get a new tool, I change every possible value (often I raise them to something about 200) and then... nothing. My reaction: Godamit..what wrong...the stupid tool wont work! and so on...
Then I asked Jens and it turned out that I hade to save my particle system first (suprice).. oh yeah..It got a file/ save (didnt noticed that before huh)
Now It was playing time.. Started to create everything from crazy fireworks to an attempt of doing a color fading waterfall. I ended up with something that looks like a snowstorm.

[inline:SceneViewer 2006-06-30 20-28-26-93.jpg=Snow]

chain physics

anton — Thu, 29 Jun 2006 12:29:33 -0400

After spending several hours trying to make a chain bahave like a chain(and not a snake) it finally started work. Now I really begin to understand the physics and my crativity take wings.

The success with the chain gives me the motivation to start trying out new physics models.

Effects is another funny thing. Started to play around with billboard and different lights today and
the engine have some great potential here. Just wait until I get into particles.

Finally..A gift for all the readers out there: A picture of the "hunter" enemy who you probably will se more of in the future ;-)

/Anton