Method for automatically smoothing object level of detail transitions for regular objects in a computer graphics display system

• US 6,222,555 B1
• Filed: 06/18/1998
• Issued: 04/24/2001
• Est. Priority Date: 06/18/1997
• Status: Expired due to Term

• Current Assignee: Christofferson Enterprises, LLC
• Original Assignee: Christofferson Enterprises, LLC
• Inventors: Christofferson, Carl L., Christofferson, Frank C.
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): PADMANABHAN, MANO
• Application Number:
  US09/099,587
• Time in Patent Office: 1,041 Days
• Field of Search: 345/428, 345/430, 703/1, 364/508
• US Class Current: 345/428
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

A database and execution hierarchy for computer graphics display systems that breaks LOD transitions into two functional steps. The first is the geometry transition, and the second is the detail transition, provided by texture maps. The geometric transition applies conformal fixed vertex decimation methods to create multiple levels of detail with a shared vertex coordinate database. Transitions between LOD'"'"'s are made seamless by creating the multiple LOD levels with macrogrids of fixed, non-decimated vertices. These are generated using a hierarchical approach that reduces the number of fixed points in the macrogrid at each successive level. Visual anomalies associated with color and texture transitions are reduced by using texture maps to ensure consistent detail transitions for pixels between LOD'"'"'s. The textures capture the detail information of the highest LOD using orthographic rendering on a grid matching the geometric macrogrid. Database storage size and transmission rate are optimized. Vertex storage is minimized by reuse for cospatial LOD'"'"'s. Surface normal descriptions can also be eliminated, saving substantial additional space, and reducing the setup calculations for a large portion of the scene since lighting is precalculated and can be disabled for higher LOD'"'"'s. Texture indices can also be reused for grouped LOD'"'"'s.

Claims

1. A method for automatically smoothing object level of detail transitions for regular objects in a computer graphics display system, comprising the steps of:

applying conformal fixed vertex decimation methods to create multiple levels of detail using a shared vertex coordinate database, each said object being partitioned into a regular grid of sectors, said sectors being combined to form larger sectors at a next level of detail, wherein successive levels of detail after the first are paired; and

creating texture maps for said paired levels, to provide detail transition, said texture maps being generated from an orthographic view of said regular object for the larger of the sectors of the levels so paired.

4. The method of claim 1, wherein said conformal decimation is applied to a first level of each said pair only to the point of eliminating coplanar polygons.

5. The method of claim 1, wherein lighting is pre-rendered in said texture map at said first level of detail and wherein lighting and interpolation calculations are disabled at run-time for said levels of detail beyond the first.

2. A method for automatically smoothing object level of detail transitions for a regular object in a computer graphics display system, said display system representing said regular object as a grid of three dimensional datapoints, comprising the steps of:

creating a conformally optimal polygonalization of said datapoints, and applying textures thereto;

partitioning said datapoints into base sectors, said base sectors being viewed as a regular grid from a view which is orthographic with respect to said regular object;

partitioning said regular grid into one or more successive pairs of finer grained sectors and coarser grained sectors, said finer grained sectors being bounded by lower level partition lines and said coarser grained sectors being bounded by higher level partition lines, said higher level partition lines being a subset of said lower level partition lines, wherein for the first of said successive pairs said finer grained sector is said base sector, and wherein said lower level partition lines of any pair beyond said first pair are a subset of the higher level partition lines of the immediately preceding pair;

creating, for each said pair of sectors, texture maps for said coarser grained sectors, said texture maps being generated from said orthographic view of said regular object'"'"'s optimal polygonalization and applied textures;

creating a level of detail pair, corresponding to each said pair of finer and coarser grained sectors, comprising a lower level of detail and a higher level of detail, respectively, said lower level of detail being created by performing conformal decimation of said datapoints after fixing said datapoints which are along said lower level partition lines, and said higher level of detail being created by performing conformal decimation of said datapoints after fixing said datapoints which are along said higher level partition lines;

applying said texture maps to both levels of said detail pair; and

transitioning to coarser levels of detail at runtime in accordance with a transition criteria.

3. An apparatus for automatically smoothing object level of detail transitions for a regular object in a computer graphics display system, said display system representing said regular object as a grid of three dimensional datapoints, comprising:

means for creating a conformally optimal polygonalization of said datapoints, and applying textures thereto;

means for partitioning said datapoints into base sectors, said base sectors being viewed as a regular grid from a view which is orthographic with respect to said regular object;

means for partitioning said regular grid into one or more successive pairs of finer grained sectors and coarser grained sectors, said finer grained sectors being bounded by lower level partition lines and said coarser grained sectors being bounded by higher level partition lines, said higher level partition lines being a subset of said lower level partition lines, wherein for the first of said successive pairs said finer grained sector is said base sector, and wherein said lower level partition lines of any pair beyond said first pair are a subset of the higher level partition lines of the immediately preceding pair;

means for creating, for each said pair of sectors, texture maps for said coarser grained sectors, said texture maps being generated from said orthographic view of said regular object'"'"'s optimal polygonalization and applied textures;

means for creating a level of detail pair, corresponding to each said pair of finer and coarser grained sectors, comprising a lower level of detail and a higher level of detail, respectively, said lower level of detail being created by performing conformal decimation of said datapoints after fixing said datapoints which are along said lower level partition lines, and said higher level of detail being created by performing conformal decimation of said datapoints after fixing said datapoints which are along said higher level partition lines;

means for applying said texture maps to both levels of said detail pair; and

means for transitioning to coarser levels of detail at runtime in accordance with a transition criteria.