Efficient scenery object rendering

• US 7,158,135 B2
• Filed: 03/08/2005
• Issued: 01/02/2007
• Est. Priority Date: 03/11/2002
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Waskey, Jason L., Santodomingo, Victor, Dent, Jason M.
• Primary Examiner(s): Zimmerman; Mark
• Assistant Examiner(s): Santiago; Enrique L.
• Application Number:
  US11/079,154
• Publication Number:
  US 20050156928A1
• Time in Patent Office: 665 Days
• Field of Search: None
• US Class Current: 345/428
• CPC Class Codes: G06T 15/00 3D [Three Dimensional] image rendering
• CPC Class Codes: G06T 15/40 Hidden part removal
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 2210/36 Level of detail

Abstract

The number of graphic objects in a visual tile rendered varies as a function of distance between the tile and a viewpoint in a simulation. Fewer objects are rendered when the tile is far from the viewpoint, and vise versa. A level of detail (LOD) value is pseudo-randomly selected and associated with each object, indicating the maximum distance at which the object will be visible. A current LOD value is determined for the tile. An object is rendered if its LOD value is equal or greater than the current LOD value of the tile. Objects are faded into and out of view by modulating an opacity value as the current LOD value changes. Texture values of an object are adjusted as a function of ambient and direct components of light on the object, to achieve lighting corresponding to time of day, current season, and/or region in the simulated world.

Claims

1. A method for efficiently rendering graphic objects within a visual tile that is included in a plurality of visual tiles of an electronic simulation, so that a number of the graphic objects that are visible in the visual tile from a viewpoint varies with a distance between the viewpoint and the visual tile, comprising the steps of:

(a) for each graphic object in the visual tile, pseudo-randomly selecting a level of detail (LOD) value for inclusion in data defining the graphic object, said LOD value being thus associated with the graphic object and indicating a maximum relative distance between the viewpoint and the visual tile at which the graphic object will be visible in the electronic simulation;

(b) determining a current LOD value for the visual tile as a function of the distance between the visual tile and the viewpoint in the electronic simulation;

(c) comparing the current LOD value for the visual tile with the LOD values that were pseudo-randomly selected for each of the graphic objects in the visual tile to determine the graphic object that are visible for the current LOD value; and

(d) rendering and displaying each graphic object that is visible for the current LOD value of the visual tile, so that the number of the graphic objects visible in the visual tile increases as the distance between the visual tile and the viewpoint decreases.

2. The method of claim 1, wherein the step of pseudo-randomly selecting an LOD value comprises the steps of:

(a) determining a seed value as a function of a location of the visual tile in the electronic simulation;

(b) generating the LOD value as a function of the seed value; and

(c) assigning the LOD value to the graphic object.

3. The method of claim 1, wherein the step of determining a current LOD value for the visual tile comprises the steps of:

(a) detecting that the visual tile is within a predefined maximum range of the viewpoint;

(b) determining the distance between the visual tile and the viewpoint; and

(c) determining the LOD value associated with the distance that was determined in the preceding step.

4. The method of claim 1, wherein the step of rendering each graphic object comprises the steps of:

(a) determining a mapping of a texture to a size of the graphic object according to an integral cell size of the texture such that an integral cell of the texture is not divided;

(b) applying the texture to at least one surface of the graphic object according to the mapping; and

(c) displaying the graphic object with the texture applied to the graphic object.

5. The method of claim 1, wherein the step of rendering the graphic objects comprises the step of changing an opacity factor over a period of time to vary a visibility of the graphic objects as a function of the LOD value associated with the graphic objects and the distance between the viewpoint and the visual tile, causing said graphic objects to fade into view as the distance between the viewpoint and the visual tile decreases and to fade out of view as the distance between the viewpoint and the visual tile increases.

6. The method of claim 1, wherein the step of rendering includes the step of rendering each graphic object as one of:

(a) a solid graphic object, such that the step of rendering the graphic object as the solid graphic object comprises the step of displaying a plurality of adjacent surfaces of the graphic object in accordance with the data defining the graphic object and by applying textures to each surface of the graphic object that is visible; and

(b) an orthogonal-plane graphic object, such that the step of rendering the orthogonal-plane graphic object comprises the step of displaying a pair of orthogonal planes in accordance with the data defining the graphic object and applying textures to the orthogonal planes.

7. The method of claim 1, wherein the data defining the graphic object comprises at least one of a location within the visual tile, a height, a width, a depth, an orientation, and a texture to be applied to the graphic object.

8. A system for efficiently rendering graphic objects within a visual tile that is included in a plurality of visual tiles of an electronic simulation, so that a number of the graphic objects that are visible in the visual tile from a viewpoint varies with a distance between the viewpoint and the visual tile, comprising:

(a) a processor;

(b) a display in communication with the processor; and

(c) a memory in communication with the processor and storing machine instructions that cause the processor to;

(i) for each graphic object in the visual tile, pseudo-randomly select a level of detail (LOD) value for inclusion in data defining the graphic object, said LOD value being thus associated with the graphic object and indicating a maximum relative distance between the viewpoint and the visual tile at which the graphic object will be visible in the electronic simulation;

(ii) determine a current LOD value for the visual tile as a function of the distance between the visual tile and the viewpoint in the electronic simulation;

(iii) compare the current LOD value for the visual tile with the LOD values that were pseudo-randomly selected for each of the graphic objects in the visual tile to determine the graphic object that are visible for the current LOD value; and

(iv) render each graphic object that is visible for the current LOD value of the visual tile, so that the number of the graphic objects visible in the visual tile increases as the distance between the visual tile and the viewpoint decreases.

9. The system of claim 8, wherein the machine instructions that cause the processor to pseudo-randomly select an LOD value, cause the processor to:

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(a) determine a seed value as a function of a location of the visual tile in the electronic simulation;

(b) generate the LOD value as a function of the seed value; and

(c) assign the LOD value to the graphic object.

10. The system of claim 8, wherein the machine instructions that cause the processor to determine a current LOD value for the visual tile, cause the processor to:

(a) detect that the visual tile is within a predefined maximum range of the viewpoint;

(b) determine the distance between the visual tile and the viewpoint; and

(c) determine the LOD value associated with the distance that was determined in the preceding step.

11. The system of claim 8, wherein the machine instructions that cause the processor to render each graphic object, cause the processor to:

(a) determine a mapping of a texture to a size of the graphic object according to an integral cell size of the texture such that an integral cell of the texture is not divided;

(b) apply the texture to at least one surface of the graphic object according to the mapping; and

(c) display the graphic with the texture applied to the graphic object.

12. The system of claim 8, wherein the machine instructions that cause the processor to render the graphic objects, cause the processor to change an opacity factor over a period of time to vary a visibility of the graphic objects as a function of the LOD value associated with the graphic objects and the distance between the viewpoint and the visual tile, causing said graphic objects to fade into view as the distance between the viewpoint and the visual tile decreases and to fade out of view as the distance between the viewpoint and the visual tile increases.

13. The system of claim 8, wherein the data defining the graphic object comprises at least one of a location within the visual tile, a height, a width, a depth, an orientation, and a texture to be applied to the graphic object.