[PCGH Extreme] Technical Q&A S.T.A.L.K.E.R. Clear Sky


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We had the chance to talk with the makers of S.T.A.L.K.E.R.: Clear Sky about their upcoming game. Igor Lobanchikov, Lead Graphics Programmer, was kind enough to answer our questions.


Our interview partner, Igor Lobanchikov

PCGH: Will the technical base of Clear Sky be a revised and enhanced version of the X-Ray Engine or do you decide to develop a new technology from scratch for the S.T.A.L.K.E.R. prequel? If this is the case what where the reasons to do so?

Weve decided to improve existing X-Ray Engine in order to deliver even better game than the original S.T.A.L.K.E.R. was.

PCGH: If you revise or enhance your technology what were the reasons you develop a technically improved engine build for Clear Sky. What technical features could not be realized with the old build of the engine? Can you give us an overview about the technical features that will be improved, reprogrammed or even added?

Developing a completely new technology for a prequel game would be an overkill. On the other hand, the existing engine is rather powerful and flexible, so we decided to polish out what was already done and to extend existing systems. For example, dynamic obstacle avoidance for NPCs was added, animation system supports IK, new eye-candy effects were added to the renderer. Our work is not about reprogramming what was already done, its more about evolving of what currently exists.

PCGH: First announcements promise a polished up visual presentation. Can you give concrete examples? How has the renderer to be reprogrammed to realize these improved visuals? What new rendering techniques where integrated with the new iteration of the engine?

One year is quite a big time period for the game industry. Graphics technology evolves, as well as hardware becomes more powerful. New rendering techniques appear. Since our game is well known for its realistic picture we have chosen techniques that add even more realism to what you see on screen. Sun shafts (which are also known as God rays) were added. Depth of field and screen space ambient occlusion add even more depth to the picture. Particles and water were enhanced: we did our best to remove hard, unnaturally looking edges between particles/water and solid objects. Most of the changes were made to better utilize deferred shading technology benefits.

PCGH: When testing S.T.A.L.K.E.R. Shadow of Chernobyl we found out that under DX9 Multisampling FSAA could not be activated when the renderer utilizes deferred shading to display the dynamic lighting with many light sources. Are you aware of that problem and will it be fixed with the new iteration of the engine?

Multisampling FSAA that is widely used for the forward rendering, is not available for the deferred shading due to the limitations of this technology. There are techniques that can be used for DX10 to use a combination of hardware and software FSAA, however they are too expensive to use them for the current generation of hardware.

PCGH: Another thing we found out is that SLI or Crossfire didnt increase the performance very much. Will that change with the improved build of the engine? Will you do further tests how the renderer could be optimized for multi GPU Settings?

We are working closely with NVidia to optimize performance both for SLI and single-GPU configurations.

PCGH: Quad-Core-CPUs become more popular and even affordable because the prices are cut. Will the new build of the engine be optimized for this kind of hardware and can players with an Intel Core Quad or AMDs K10 expect a remarkable performance boost? If yes will there be higher amount of separate threads or how is problem solved technically?

We are not planning to change overall architecture of the X-Ray engine. However, were trying to get everything we can from the newer hardware, including Quad-Core-CPUs.

Questions concerning the DX10 support in S.T.A.L.K.E.R.

PCGH: In our last interview your programmers said that the next iteration of the X-Ray Engine will fully support the new DX10 API of Microsoft vista? Is that the case? Will S.T.A.L.K.E.R. Clear Sky fully utilize the possibilities of Direct X 10? What are the general advantages of that API? Can you give examples taking the games visual as well as performance into consideration?

We are going to add the support of DX10 API, however, I cant currently tell you anything specific, even if it would be supported at all. Its massive work to be done and experiments are being carried out as we speak.

PCGH: Had you designed your engine to utilize Direct X 10 form ground up or did you patch in support for DX10 later?

X-Ray was designed to support multiple renderers, however, it needs to be refactored in order to support DX10.

PCGH: Do you use advanced features of Direct X 10 like Geometry Shader, Virtual Texture Management etc.? Can you please give examples how they are utilized? In what way do these features improve or simplify the rendering process?

We are in progress experimenting with DX10, and still deciding what feature should be integrated into the final version. We are going to use geometry shaders, since some really nice effects require them. Rendering to volume textures could possibly be used

PCGH: Will the DX10 visualization differ substantially from the graphics that are rendered with DX9 hardware? What are the visuals in S.T.A.L.K.E.R. Clear that can only be rendered with shader model 4 hardware? Will there be any significant in performance between the DX9 an DX10 version of the game?

Currently its really hard to say anything specific about DX10 final picture/speed, since we are experimenting with it a lot.

PCGH: How much of a performance hit will the improved optics of DX10 incur? With all details maxed out is a typical first gen DX10 card already running at its limits or is it possible to play the DX10 version of Clear Sky with all details in 1.024x768 with a middleclass DX10-Card like the Geforce 8600 GTS or HD2600 XT?

Well, even DX9 render path would make an advantage of faster graphics card, since some of our effects are rather resource-consuming, when they are maxed out. DX10 version would definitely need the latest hardware to allow you enjoy all the advantages of the enhanced renderer.

PCGH: Will your new game be vista only? If yes, do you support a fallback for Vistas DX 9 renderpath?

Prequel will definitely support WinXP. It will support all previous renderers for both WinXP and Vista and support a new one for DX10 for Vista.

PCGH: S.T.A.L.K.E.R. Shadow of Chernobyl utilized the ODE physics engine for a powerful and realistic physics engine including vehicle physics that were not applied? Will you keep the engine or did you decide to utilize a physic middleware? Will it be possible to use vehicles in Clear Sky?

Currently we are going to use physics engine that was used in the original game. I cant say if it will be possible
to use vehicle physics.

PCGH: Have you thought about licensing the Novodex or Havok Engine to make use of hardware accelerated physic like Ageias PhysX card or Havok FX? Will your game in generally support a Physx card? What is your personal opinion about the topic?

We are not going to use physics middleware for the prequel, we are going to continue developing our current physics solution.

Since physics content is not very scalable (you can add more or less physical particles, debris and thats all), hardware physics acceleration usage is limited and I dont see the prequel could have any significant advantages using physics acceleration.

PCGH: Will the minimum and recommended hardware requirements be much higher compared to the first S.T.A.L.K.E.R. part? What rig would you recommend to play Clear Sky in 1.280x1.024 without and with 4x FSAA/8:1 AF?

Youll be able to play prequel on the hardware that you played the original game. However, if you are going to see all new effects at their best youll have to use latest graphics boards.

PCGH: Thanks for the interview!


Other gaming related interviews on PCGH Extreme:
Interview with id:"What do you think about AMDs triple core approach?"
Interview: Tim Sweeney (Epic) talks Triple-Core
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Sorry aber nutz das doch um euer Englisch zu trainieren, ich weiß nicht wie weit du da draußen in einer größeren Firma kommst ohne englisch. Bei uns ist dies sogar Ausschlußkriterium


Nee, oder?

PCGH: Viererkabel-Kern-CPUs werden populäreres und gleichmäßigeres erschwingliches, weil die Preise geschnitten werden.
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