MultiResolution Mesh in Dark Reign II

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Multi-Resolution Mesh in Dark Reign II
March 18, 1999
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respective owners
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Who are we?

• Pandemic Studios
• Developing Dark Reign II and Battlezone 2
• Dark Reign II
• Sequel to popular RTS Game

John Cooke 3D Programmer Dark Reign II
Rick Glenn Art Director Dark Reign II
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Dark Reign II Design Philosophy

• Stay Traditional Real Time Strategy
• Base Building, Resource Management, Big Battles

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Dark Reign II Design Philosophy

• True 3D
• Player controlled camera
• True Scale
• Night/Day
• Physics
• Infantry based
• Detailed units and animations
• Fifa-style

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The Problem
RTS means lots of units RTS means large
views Detailed infantry means tons of
polys Pentium 550 with Voodoo 3 minimum
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Searching for a solution

• Static LOD
• The way weve always done it
• Tessellation
• Messiah
• Multi-Resolution Mesh (MRM)
• IALs latest 3D Software Technology

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What is MRM

• MRM allows SMOOTH real time polygon reduction of
  meshes.

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Why use MRM?

• Scalability
• real time frame rate control via polygon
  reduction.
• Visual quality
• increase foreground detail by reducing
  background.
• better in game engine cut scenes.

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Why use MRM?

• Flexibility
• author only once for each unit
• tweak unit counts
• generate static LODs
• MultiRes Software Toolkit consists of
• MRMGEN.dll integrate into authoring tool.
• MRM plug in for MAX generates MRM files.
• MRM Data from an export file

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Integration into Code

• MRM runtime is very simple.
• No run time tesselation or data generation of any
  kind. All mesh data is pre-allocated.
• Data describes how faces should re-index their
  vertex data to display a mesh at various
  resolutions.
• Easy to integrate with any graphics engines mesh
  data format.

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Integration into Code

• MRMGEN does a lot of complex decision making to
  generate the runtime data
• Integration programmer doesn't need to know how
  it works.
• It uses only the meshes original data,
  determining the least important vertex at each
  resolution level.
• It attempts to keep texture and normal
  distortions to a minimum for as long as possible.

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Integration into Code

• Works best with a continuous skin, but not
  absolutely necessary.
• MRMGEN doesnt accept data from multiple meshes.
• MultiRes Modifier plugin generates MRM files
  directly from Max.
• MultiRes Software Toolkit provides code for
  loading and saving MRM data.

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Tool Integration

• Write a simple mesh viewer application with your
  graphics library for development.
• Integrate the MRMGEN.dll directly into the tool
  and generate custom file format including MRM
  data.
• Provides artists a quick and easy way to see
  their assets in the game.

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Data structures

• Integration is easier for continuous-skin mesh
  data structures
• Continuous-skin, envelope animated models are
  typical for most current games
• Only requirement is vertex and face data must
  exist in contiguous arrays
• Meshes have separate arrays of vertex positions,
  normals, texture coordinates, and faces
• Each face has 3 sets of indexes 1 each for
  vertex position, normal, and texture uv
• Could use other formats i.e. 1-to-1 mapping for
  vertex, normal, and uv
• IMESH accepts custom data records and keeps track
  of them for you.

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Data structures

• MRMGEN generates MRM update records and optimizes
  the mesh
• One Vertex Update Record for each vertex in the
  mesh.
• Each contains a number of faces to
  increase/decrease and a collection of Face Update
  Records.
• One Face Update for each face vertex attribute to
  change position, normal, uv.

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Data Structures

• typedef struct MRMUpdatesTag
• unsigned long maxNumVertices
• unsigned long maxNumFaces
• unsigned long maxNumNormals
• unsigned long maxNumTexCoords
• VertexUpdate vertexUpdates // one for each
  vertex in the mesh
• MRMUpdates

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Data Structures

• typedef struct VertexUpdateTag
• unsigned long vertexIndex
• unsigned long parentVertexIndex
• unsigned long numNewFaces
• unsigned long numNewNormals
• unsigned long numNewTexCoords
• unsigned long numFaceUpdates
• FaceUpdate faceUpdates // typically 2
• VertexUpdate

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Data Structures

• typedef struct FaceUpdateTag
• unsigned long faceIndex
• AttribToken attrib // Vertex, Normal, or
  TexCoord
• Unsigned long value2 // New attrib index
  Increasing or Decreasing
• FaceUpdate

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Data structures

• Resolution change is achieved by traversing the
  update records.
• Only records for the vertices being removed or
  added are looped
• Vertex data is sorted by decreasing order of
  importance so LOD changes are minimal hit on the
  cache.
• Important as mesh polygon count increase
• MRM data is typically about the same size as the
  mesh data itself.

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Runtime

• Distance from the camera is a good primary
  polygon reduction metric
• Since detail is wasted in the background, get rid
  of it.
• Increase your polygon budget for the foreground,
  or for more units, effects, etc.
• Frame rate is another great metric
• Extra reduction for when frame rate drops below
  threshold.

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3DSMax vs. Softimage

• Digimation MultiRes tools for 3DS Max.
• 3DS plug-in lets artists hand tweak MRM
  parameters and see the results in real-time.
• Dialogs for
• Vertex Merging Threshold merge vertices of
  distinct groups MRMGEN optimizes mesh.
• Maintain Base Vertices maintains vertices
  selected when MRMGEN is invoked.
• Boundary Metric keep materials distinct at the
  expense of reduction.
• Multiple Normals per Vertex with Crease Angle
  specification.
• Gives programmers an instant game friendly format
  and code toolkit.

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3DSMax vs. Softimage

• For Softimage you need to write your own plug-in
  or custom tool.
• Dark Reign II uses a custom tool along with some
  versatile tricks
• Frog Pose

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Production Application

• MRM allows for better art
• MRM saves time
• More Time More Art
• MRM gives peace of mind

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Concept

• Shoot for a higher ideal
• Can think about the high end
• Less low end issues than with Static LODs

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Author Once

• One Time Authorship of Assets
• One High poly rather than several Low poly
• Animate one model
• Dont have to deal with transfer of animations

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Dark Reign II Unit created at 800 polys
Time to create unit 1 Day
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Interstate 76 Car at 300 Polys
Time to create car 1 Day
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Static LODs then created at 200, 100, and 75
polys
Time to create static LODs 1 Day
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Dark Reign II assets MRMd to 800, 500, 300 polys
Time to create Continuous LODs 0 days
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Art team can create two MRMd assets in time it
takes to create one asset using static LODs
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How does number of polys in source model affect
MRMing?
1200 poly model
800 poly model
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Both models at 800 polys
1200 poly source
800 poly source
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Both models at 500 polys
1200 poly source
800 poly source
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Both models at 300 polys
1200 poly source
800 poly source
Result - No penalty for Higher Source Model
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Better Than Static LODs

• Less production time
• Able to experiment more
• No popping
• Easier to change an asset
• Dial-In MRMing on a per asset basis

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Better Frame Rate During Production

• Code rarely optimized early on
• Lack of static LODs early on
• How many times do you run the game
• Easier to experiment

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Peace of Mind

• Proven technology
• Trying to project ahead to system spec is
  difficult 1 to 2 years before release
• High visuals vs. Frame Rate
• Take a lot of risk in production
• Its usually pretty late in the production when
  you decide to either reduce polys or optimize
  engine

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Bigger Sweet Spot

• Low end versus high end
• Low end 166 with Voodoo 1
• High end 550 with TNT2
• How do we make a great game for all systems

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Longer Legs

• Art made higher than intended target
• Game will look better as machines get faster

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Art Considerations

• Fewer texture and normal discontinuities is
  better for MRM
• Mesh is more efficient with fewer discontinuities
• Trade off between discontinuities and efficient
  use of texture space

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Is MRM right for you

• Why do we like MRM
• easy to use
• increases frame rate without degrading visual
  quality.
• Who can use MRM
• anyone writing a 3D game that displays
  significant perspective reduction. i.e. everybody!

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Is MRM right for you

• Things to consider when considering using MRM in
  your project
• how else are you going to compete in the brave
  new world of super-scalability