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The success of Sierras Creative Interpreter (SCI)

Whether it's the incredible graphics, the beautiful music or the original detailed stories, you loved the classic adventure games released in the 80's and 90's by Sierra On-line. Space Quest, Leisure Suit Larry, King's Quest and many more games really changed the world of PC gaming. Sierra always tried to make use of the latest PC technologies, and for this they created one of the most versatile game engines ever made: Sierra's Creative Interpreter. In this article, we'll show you what made this engine so great. But first, let's take a look at the history of this engine.

In 1983, IBM announced the PCjr: a personal computer marketed to be home-friendly and with better graphics and sound capabilities. This PC could display 320x200 pixels graphics with 16 colors, and it could play three sinus voices and a white noise at the same time. The PCjr could perform flicker-free animation and other effects that were either difficult or impossible to produce on contemporary PC clones.

To promote their new personal computer, IBM funded Sierra On-Line $700.000 to develop a game that would fully show off the PCjr's capabilities. Sierra created the groundbreaking adventure game engine called Adventure Game Interpreter (AGI). Altough the PCjr could display 320x200 graphics, the graphics in AGI games were only 160x200 pixels because of memory restrictions.

AGI in King's Quest
AGI in King's Quest
Games like Leisure Suit Larry and Space Quest that used this engine were marketed as 3-D Animated Adventure Games. What made these games truely unique was that they allowed game characters and objects to move freely around on screen, in front of and behind other objects. To do this, the AGI interpreter used special 'priority screens' for each background screen, which indicated where objects on screen are in 3D space. The priority screens also made it easy to trigger events, such as falling from a cliff, or entering doors.

SCI0 in Leisure Suit Larry Goes Looking for Love
SCI0 in Leisure Suit Larry Goes Looking for Love
In September of 1988, Sierra upped the ante once more and released noteworthy adventure games King’s Quest IV, Police Quest II and Leisure Suit Larry II. These games where the first to make use of Sierra's new engine, SCI (Sierra’s Creative Interpreter). It was now possible to use 320x200 16 color graphics, synthesized FM MIDI music and sound effects, and mouse control and pop-up input box control. SCI was designed to be much more complex and versatile to no specific type of game. SCI was designed more as a portable virtual machine rather than a simple adventure game engine. It was way ahead of it 's time – an object-oriented virtual machine years before Java. It supported 128 kernel instructions such as 'ShakeScreen', 'DoSound', 'SaveGame', etc.

SCI1 in Space Quest IV
SCI1 in Space Quest IV
In 1990 Sierra released SCI1, which supported 256 color graphics, a completely mouse driven interface, digitized sound and later movie support. Artwork for SCI1 game scenes were usually acrylic paintings on illustration board which was then digitally scanned into the computer's memory.

SCI2 in King's Quest VII: The Princeless Bride
SCI2 in King's Quest VII: The Princeless Bride
Finally, SCI2 and later SCI3 were released, and suddenly it was possible to use hi-res 640x480 256 color graphics, digitized cd quality music and full motion video. Famous SCI2 and SCI3 games are Space Quest 6, King's Quest VII, Shivers and later Leisure Suit Larry 7. When open source SCI engines like FreeSCI were developed, it became possible to uncover unused game elements, ranging from pencil sketches to complete new rooms and art. There even are famous blooper clips from the Space Quest 6 voice actors.

A dedicated proponent of emerging technologies, Sierra made use of each generation of digital audio card as they came along, gradually improving their games’ scores with the advancing hardware. Ad-Lib, SoundBlaster and Roland have all undeniably sold a great, great deal more sound cards thanks to players who wanted a fuller traipse through the worlds of the Sierra master crafters. Sierra was focused on using new hardware – such as the storage capacity of CD-ROMs – to develop ways to create immersive and fanciful game worlds. Creating ever-more detailed and colourful environments, rich musical scores, and even professionally voiced speech all contributed to the success of one of the most complex and versatile engines of it's time.



djquu (3 years ago)
I would say that Larry 7 was closest Sierra ever came to perfection; point-and-click interface with a free-text parser. I can't believe they screwed things up from that point on like they did with all the "true 3D"-nonsense and FMV-flood.
Joe (3 years ago)
SCI1 did not implement the icon interface itself. That was up to the game designer. In fact, a lot of Space Quest IV was designed with a command parser before management politics intervened and forced the point-and-click interface onto the project.
Gildas (6 years ago)
Holy shzniit, this is so cool thank you.

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