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Introducing the Computer Graphics Pipeline

The 6 Phases of 3D Production

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There is a point in nearly every film-goer’s life when he sees something in a movie and wonders, “now how on earth did they do that?”

Some of the images that have been created for the silver screen are truly astounding, from the earth-shaking battles in The Lord of the Rings trilogy, to the mesmerizing digital environments produced for Avatar, Tron: Legacy, and 2010′s visual effects champion, Inception.

When you look deep under the hood, there is a tremendous amount of sophisticated math and science that goes into modern computer graphics.  But for every computer scientist working behind the scenes, there are three or four digital artists working hard to bring the creatures, characters, and landscapes of their imaginations to life.

The Computer Graphics Pipeline

The process that goes into the production of a fully realized 3D movie character or environment is known by industry professionals as the “computer graphics pipeline.”  Even though the process is quite complex from a technical standpoint, it’s actually very easy to understand when illustrated sequentially.

Think of your favorite 3D movie character.  It could be Wall-E or Buzz Lightyear, or maybe you were a fan of Po in Kung Fu Panda.  Even though these three characters look very different, their basic production sequence is the same.

In order to take an animated movie character from an idea or storyboard drawing to a fully polished 3D rendering, the character passes through six major phases:

  1. Pre-production
  2. 3D Modeling
  3. Shading & Texturing
  4. Lighting
  5. Animation
  6. Rendering & Post-production

1. Pre-Production

In pre-production, the overall look of a character or environment is conceived.  At the end of pre-production, finalized design sheets will be sent to the modeling team to be developed.

  • Every Idea Counts: Dozens, or even hundreds of drawings & paintings are created and reviewed on a daily basis by the director, producers, and art leads.

  • Color Palette: A character's color scheme, or palette, is developed in this phase, but usually not finalized until later in the process.

  • Concept Artists may work with digital sculptors to produce preliminary digital mock-ups for promising designs.

  • Character Details are finalized, and special challenges (like fur and cloth) are sent off to research and development.

      2. 3D Modeling

      With the look of the character finalized, the project is now passed into the hands of 3D modelers.  The job of a modeler is to take a two dimensional piece of concept art and translate it into a 3D model that can be given to animators later on down the road. 

      In today's production pipelines, there are two major techniques in the modeler's toolset: polygonal modeling & digital sculpting.

      • Each has its own unique strengths and weaknesses, and despite being vastly different, the two approaches are quite complementary.

      • Sculpting lends itself more to organic (character) models, while polygonal modeling is more suited for mechanical/architectural models.

      The subject of 3D modeling is far too extensive to cover in three or four bullet points, but its something we'll continue covering in depth in both the blog, and in the Maya Training series.

      3. Shading & Texturing

      The next step in the visual effects pipeline is known as shading and texturing. In this phase, materials, textures, and colors are added to the 3D model.

      • Every component of the model receives a different shader-material to give it an appropriate look.

      • Realistic materials: If the object is made of plastic, it will be given a reflective, glossy shader. If it is made of glass, the material will be partially transparent and refract light like real-world glass. 

      • Textures and colors are added by either projecting a two dimensional image onto the model, or by painting directly on the surface of the model as if it were a canvas. This is accomplished with special software (like ZBrush) and a graphics tablet.

        4. Lighting

        In order for 3D scenes to come to life, digital lights must be placed in the scene to illuminate models, exactly as lighting rigs on a movie set would illuminate actors and actresses.  This is probably the second most technical phase of the production pipeline (after rendering), but there's still a good deal of artistry involved.

        • Proper lighting must be realistic enough to be believable, but dramatic enough to convey the director’s intended mood.

        • Mood Matters: Believe it or not, lighting specialists have as much, or even more control than the texture painters when it comes to a shot’s color scheme, mood, and overall atmosphere. 

        • Back-and-Forth:   There is a great amount of communication between lighting and texture artists.  The two departments work closely together to ensure that materials and lights fit together properly, and that shadows and reflections look as convincing as possible.

        5. Animation

        Animation, as most of you already know, is the production phase where artists breathe life and motion into their characters.  Animation technique for 3D films is quite different than traditional hand drawn animation, sharing much more common ground with stop-motion techniques:

        • Rigged for Motion: 3D characters are controlled by means of a virtual skeleton or "rig" that allows an animator to control the model's arms, legs, facial expressions, and posture.

        • Pose-to-Pose: Animation is typically completed pose-to-pose.  In other words, an animator will set a “key-frame” for both the starting and finishing pose of an action, and then tweak everything in between so that the motion is fluid and properly timed.

        Jump over to our computer animation companion site for extensive coverage of the topic.

          6. Rendering & Post-Production

          The final production phase for a 3D scene is known as rendering, which essentially refers to the translation of a 3D scene to a finalized two dimensional image.  Rendering is quite technical, so I won’t spend too much time on it here. In the rendering phase, all the computations that cannot be done by your computer in real-time must be performed.

          This includes, but is hardly limited to the following:

          • Finalizing Lighting: Shadows and reflections must be computed.

          • Special Effects: This is typically when effects like depth-of-field blurring, fog, smoke, and explosions would be integrated into the scene.

          • Post-processing: If brightness, color, or contrast needs to be tweaked, these changes would be completed in an image manipulation software following render time.

          We've got an in-depth explanation of rendering here: Rendering: Finalizing the Frame

            7. Want to learn more?

            Even though the computer graphics pipeline is technically complex, the basic steps are easy enough for anyone to understand.  This article is not meant to be an exhaustive resource, but merely an introduction to the tools and skills that make 3D computer graphics possible.

            Hopefully enough has been provided here to promote a better understanding of the work and resources that go into producing some of the masterpieces of visual effects we’ve all fallen in love with over the years.

            Keep in mind, this article is just a jumping off point—we discuss all of the topics raised here with greater detail in other articles.  In addition to About.com, art books for specific films can be eye opening, and there are vibrant online communities at places like 3D Total and CG Society.  I urge anyone with a further interest to check them out, or if you've got an interest in making some art of your own, take a look at our tutorial series:

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