Resolution-independent method for displaying a three-dimensional model in two-dimensional display space

• US 5,745,666 A
• Filed: 02/21/1996
• Issued: 04/28/1998
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Gilley, Glenn G., Tebbs, Brice W.
• Primary Examiner(s): Nguyen, Phu K.
• Assistant Examiner(s): BUCHEL JR, RUDOLPH JOHN
• Application Number:
  US08/604,195
• Time in Patent Office: 797 Days
• Field of Search: 395/119, 395/130-131, 395/126-128, 395/133, 395/123
• US Class Current: 345/428
• CPC Class Codes: G06F 15/00 Digital computers in general details G06F1/00 – G06F13/00; Data processing equipment in general
• CPC Class Codes: G06T 15/00 3D [Three Dimensional] image rendering
• CPC Class Codes: G06T 15/04 Texture mapping
• CPC Class Codes: G06T 15/10 Geometric effects

Abstract

A method for rendering a graphics image of a three-dimensional graphics model is described. The method consists of the steps of projecting a parametric surface representation of the three-dimensional graphics model into a two-dimensional parametric space; mapping an array of grid points onto the parametric space; evaluating a shading function at each grid point to form an array shading values; applying a contouring function to the array of shading values to determine boundary curves for regions of constant shading; applying a silhouette function to the parametric surface representation of the three-dimensional graphics model to determine the boundaries for regions of consistent-facing; clipping the regions of constant shading by the regions of consistent-facing to determine consistent-facing regions of constant color; mapping the regions of constant shading back to the surface of the three-dimensional model; occluding hidden surfaces; mapping the clipped regions of constant shading to display space; and filling the regions of constant shading in display space. The regions of constant shading are available for editing by a two-dimensional drawing package.

Claims

1. A method of rendering a three-dimensional model having a three-dimensional surface, comprising:

storing a resolution-independent three-dimensional model including a three-dimensional surface in a computer-readable form;

defining a resolution-independent two-dimensional parametric space on the three-dimensional surface by mapping the three-dimensional surface to the two-dimensional parametric space;

applying a shading function to an array of grid points defined on the resolution-independent two-dimensional parametric space to compute a grid point shading value at each of the grid points;

applying a contouring function to the computed grid point shading values to provide resolution-independent curves defining regions of constant shading in the parametric space;

projecting the three-dimensional model to a display space to create a resolution-independent two-dimensional representation of the model including visible portions of the curves defining regions of constant shading; and

rendering the resolution-independent representation of the model created in display space.

2. The method of claim 1 further comprising:

applying a silhouette function to the two-dimensional parametric representation of of the surface to determine boundaries for regions of consistent facing; and

clipping the regions of constant shading by the regions of consistent facing to determine consistent-facing regions of constant color.

3. The method of claim 1 wherein the three-dimensional model is composed of one or more bicubic patch meshes.

4. The method of claim 1 wherein said three-dimensional model has a color, said method further comprising:

specifying a first illumination color;

specifying a second illumination color;

specifying a threshold value;

computing a blend factor corresponding to a fractional weight between said three-dimensional model color and said first illumination color if said blend factor is less than or equal to said threshold value, and said blend factor corresponds to a fractional weight between the three-dimensional model color and said second illumination color if said blend factor is greater than said threshold value.

5. The method of claim 1 wherein the array of grid points on the two-dimensional parametric space has a spacing determined from a parameter specified interactively by a user of a computer program embodying the method.

6. The method of claim 1 wherein:

the rendered regions of constant shading are transmitted to a printing device in a resolution-independent form; and

filling the regions of constant shading is performed by the printing device.

7. A computer implemented method of displaying a three-dimensional model having one or more surfaces, the method comprising the computer controlled steps of:

storing a resolution-independent three-dimensional model including a three-dimensional surface in a computer-readable form;

defining a resolution-independent two-dimensional parametric space on the three-dimensional surface by mapping the three-dimensional surface to the two-dimensional parametric space;

applying a shading function to an array of grid points defined on the resolution-independent two-dimensional parametric space to compute a grid point shading value at each of the grid points;

applying a contouring function to the computed grid point shading values to provide resolution-independent curves defining regions of constant shading in the parametric space;

determining the boundaries of consistent-facing regions of the three-dimensional model in the two-dimensional parametric space;

clipping the regions of predetermined shading by the boundaries of the consistent-facing regions to derive consistent-facing regions having the predetermined shading;

mapping the derived consistent-facing regions to display space; and

displaying the mapped consistent-facing regions.

8. The method of claim 7 wherein the shading function is constant shading.

9. The method of claim 7 wherein the boundaries of the consistent-facing regions are determined by applying a silhouette function to the parametric surface representation of the three-dimensional model.

10. The method of claim 7 wherein the three-dimensional model is composed of one or more bicubic patch meshes.

11. The method of claim 7 wherein the selecting of the surface regions of predetermined shading and the determining of the boundaries of the consistent-facing regions are performed concurrently.

12. The method of claim 7 wherein the shading function is:

space="preserve" listing-type="equation">v=(S N+d)r

where

v is an output shading value;

S is a light source illumination vector;

N is a surface normal at said grid point;

d is a diffuse illumination constant; and

r is reflectivity of a surface of said three-dimensional model at said grid point.

13. The method of claim 7 wherein said three-dimensional model has a color, the method further comprising:

specifying a first illumination color;

specifying a second illumination color;

specifying a threshold value;

computing a blend factor corresponding to a fractional weight between said three-dimensional model color and the first illumination color if said blend factor is less than or equal to the threshold value, and the blend factor corresponds to a fractional weight between the three-dimensional model color and the second illumination color if the blend factor is greater than the threshold value.

14. The method of claim 7 wherein the regions of constant shading in display space are filled before they are displayed.