One of my older presentations from the Browser Games Forum 2011 about how we're managing data size optimizations and streaming in Drakensang Online. Absolute asset size number are about 3x..4x bigger today, since the game has grown a lot since 2011.

1. Data Management and
Streaming Strategies
in Drakensang Online
Andre “Floh” Weissflog
Head of Development Berlin
Bigpoint GmbH
Browser Games Forum 2011

2. 2
• Hack & Slay F2P MMO.
• Embedded in browser.
• No client download or installation.
• Impressive 3D graphics.
• 8 months from concept to Closed Beta.

3. 3

4. 4

5. Team & Technology Background
5
Drakensang Online is developed by the same team that also worked on the previous
single-player Drakensang “boxed titles”.
Very skilled and experienced team, very solid and proven production pipeline
and processes (and very little online experience).
The technology behind our client and server is the Nebula3 engine (~250k lines of C/C++, 12
years of continuous development).
Epic stories will be written about how we went from building offline boxed-titles to
creating an MMO running in a browser in 8 months.
…but not Today…
Today we’ll talk about data management
and streaming in Drakensang Online…

6. Data Management Core Demands
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• Browser Game Experience Click & play, no installation.
• Fast Startup Time Start in seconds, not minutes
• On-Demand Streaming: Only download what’s needed
• Client-Side Caching: CDN traffic cost, user experience
• Robustness: The web is slow and unreliable.
• Minimize Data Size: But keep graphics quality high!

7. Drakensang Online: The Assets
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• 50 interconnected maps
• 240 monsters
• 120 NPCs
• 1400 items
• 300 animated effects
317 MB uncompressed
139 MB compressed
27035 filesAsset Types
Textures
Audio
Meshes
Navigation
Locale
Maps
Anims
Other

8. Two Main Achievements
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Aggressive Data Size Reduction
We’re working with 3%of the data size we’ve been used to.
This is mainly an organizational achievement.
All departments have to agree on data size budgets…
…even if it’s hard (e.g. for the graphics guys)
Seamless Data Streaming During Gameplay
That’s mainly a programming achievement.
Client engine must support asynchronous I/O from the
ground up.

9. Maps as “static web pages”
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This was really the initial idea behind our data
management.
Our maps reference many small asset files “somewhere
on the web”, just like a static web page.
All asset files are loaded asynchronously. Render loop
can deal with assets which are not yet loaded.
Really clever local file caching prevents unnecessary
HTTP requests (down to no HTTP traffic at all if the
cache is completely up-to-date).

10. Asset Size Reduction: Extreme Granularity
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Our maps are built from really small and simple 3D objects:
Extremely granular set of
reusable objects. Each with
only a few dozen to a few
hundred triangles.
One map may have 100k of those
micro 3D objects, but only a few
dozen DIFFERENT objects.
That’s very good for data
size. But…
OMG TEH
DRAW CALLS !!
Nebula3 uses hardware
instancing and runtime-
baking to reduce draw
calls from about 5000
down to 250 per frame.

11. Asset Size Reduction: Textures
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Typical texture
dimensions:
256 x 256
128 x 128
64 x 64
All textures are DXT compressed (and then – like all other files – ZIP compressed)
Bump textures use DXT5NM compression, aka the Carmack-Trick
(that’s why they’re grey, not purple).
Texture types:
color
bump
emissive
specular
Typical download sizes for textures are somewhere between 5 kByte
and 40 kByte.
Textures are aggressively shared and reused.

12. Asset Size: Lights, Shadows& Decals
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All lighting and shadowing is completely dynamic. No light-maps needed.
We use deferred Pre-Pass-Lighting to enable “infinite point-lights” with
moderate fill-rate requirements.
Volumetric Decals are used to hide the tile-nature of the ground.
Post-Effects add bloom, fog, color saturation and color balancing.

13. Two Streaming Strategies:
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1) ON DEMAND:
Client requests data right when it’s needed.
IO requests are handled asynchronously.
May take several seconds until data is ready.
Until then:
Render a placeholder or…
Render nothing.
2) BACKGROUND STREAMING:
Low-priority background thread just for cache warm-up.
One streaming list per map created during build process.
Download and update items in local file cache.
Very speculative, can’t really predict what’s needed next.

14. The web as a (really unreliable) hard-disc
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Nebula3 always had a powerful I/O system:
• async I/O is standard, not the exception
• “massively multi-threaded”, currently 10 I/O-threads
• pluggable filesystems
• all file paths are URLs
We built an “HTTP filesystem” on top of this:
• only uses HTTP GET requests
• transparently replaces local-disc file I/O
• MD5 checksums for all files
• ZIP compression for all files
• hierarchical caching system
• directory walking and file-exists checks
• CDN support
• reasonably fail-safe (high latencies, dropped
connections, corrupt
downloads, tampering…)

15. “Massively Multi-Threaded IO”
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IO Dispatcher
Thread
Main Thread
Render Thread
Audio Thread
… Thread
Incoming IO Requests
IO Threads
Cache
(Local HD)
Cache
Hit?Yes
Web
Server
No
Update Cache
Served IO Requests
• up to 10 HTTP-GET requests concurrently in flight (tweakable)
• low-prio IO requests don’t block high-prio requests
• no difference in high-level code between file I/O and http I/O

16. Hierarchical File Cache
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ROOT MD5 KEY
e4680c8372bc6c527043a97631b404d7
Directory “Table Of Content” File
Leaf TOCs Leaf TOCs Leaf TOCs
1. Daily-Build-Process: compress files and create per-file MD5 hashes.
2. Each directory has a “Table Of Content” file with all MD5 hashes.
3. TOCs are also compressed and MD5’d.
4. ...with one single “Directory TOC” at the top.
5. …and a single Root MD5 Key for the Directory TOC.
• Client receives Root MD5 Key at startup.
• Downloads TOC files if not in cache…
• TOC files provide MD5 keys for files.
• Zero HTTP GETs if cache is up-to-date!

17. The Cache Chain
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We basically have a 3-level cache for assets:
RAM DISC
CDN
PROXY
CDN
ORIGIN
Level 1 Level 2 Level 3
RAM Cache Hit?
Resource objects are shared in RAM using their ResourceIDs.
DISC Cache Hit?
MD5-named file must exist in local file cache.
MD5 of actual file-content must match build-time MD5 hash.
CDN Proxy Cache Hit?
MD5-hash appended to HTTP GET URL, forces a cache miss if proxy only has
out-of-date file of the same name.
CDN Origin Server has the definite data.

18. 404’s Considered Harmful
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Remember this from the previous page:
RAM DISC
CDN
PROXY
CDN
ORIGIN
1st 2nd 3rd 4th
“Sh*t happens”.
Trying to load non-existing assets will happen with such a complex data set.
HTTP requests for non-existing files will cut through all the way to the origin server.
CDN’s usually cache 404’s for a few seconds, but it’s better to not bother the web servers with
404’s at all.
Our Table-Of-Content-Files let us detect non-existing files on the client without a server
roundtrip.

19. Conclusion
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• Data management is the job of the whole team.
• Careful, early asset size planning.
• Team must commit on size budgets.
• “Programming Magic” alone doesn’t solve problems.
• Programming, Level Design and Art Department must work hand in hand.
• Oh, and: Check your CDN cost plan (if you pay per HTTP request, our solution is sub-optimal)

20. Thank You 
Questions?
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21. Find us on
Bigpoint GmbH
Alexanderstraße 5
10178 Berlin
Germany
Bigpoint Inc.
500 Howard Street
Suite 300
San Francisco, CA 94105
Bigpoint Distribuição de
Entretenimento Online Ltda.
Av. Brig. Faria Lima
3729 cj. 528
04538-905 São Paulo
Brazil
Bigpoint GmbH
Andre Weissflog
Head of Development Berlin
Drehbahn 47-48
20354 Hamburg
Germany
Tel +49 40.88 14 13 - 0
Fax +49 40.88 14 13 - 11
info@bigpoint.net
www.bigpoint.net
Contact us
Bigpoint International Services
Limited
1 Villa Zimmermann
Ta’Xbiex Terrace
XBX 1035 Ta’Xbiex
Malta
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