Process for modelling a 3D scene

• US 7,113,635 B2
• Filed: 03/25/2003
• Issued: 09/26/2006
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Magnolia Licensing LLC (IP Edge LLC)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Nicolas, Yannick, Robert, Philippe
• Primary Examiner(s): MARIAM, DANIEL G
• Application Number:
  US10/396,182
• Publication Number:
  US 20030179194A1
• Time in Patent Office: 1,281 Days
• Field of Search: 382/154, 382/284, 382/285, 345/419, 345/420, 356/12, 356/13
• US Class Current: 382/154
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

A process for modeling a 3D scene is provided which comprises validating the model by determining a maximum permitted distortion (5) on a 2D synthesized image (4), generated by the approximation inherent in the model (2); calculating for a point I of a reference image (7) and on a set of synthesized images (4) representing the 3D point of the scene corresponding to this point I, of the minimum (z_i−Δ_zi¹) and maximum (z_i+Δ_zi²) depth values of the depth z_i of this point I corresponding to this maximum distortion, calculating a span around the depth z_i of this point I, dependant on the minimum value of the error Δ_zi² and on the minimum value of the error Δ_zi¹ among the values calculated for the synthesized images of the set.

Claims

1. Process for modelling a 3D scene (1) defined on the basis of reference images (7) associated with viewpoints (I) and original depth maps, by calculation of approximate depth maps describing a model, comprising the following steps:

predetermining of a maximum permitted distortion (5) on a 2D synthesized image (4), generated by the approximation inherent in the model (2),

calculating, for a point I of a reference image (7) and on the basis of a set of synthesized images (4) representing the 3D point of the scene corresponding to this point I, of the minimum (z_i−

Δ

_zi¹) and maximum (z_i+Δ

_zi²) depth values of a depth z_i of the point I corresponding to the maximum permitted distortion,

calculating a span ([z_m(i), z_M(i)]) around the depth z_i of this point I, dependant on the minimum value of the error Δ

_zi² and on the minimum value of the error Δ

_zi¹ among the values calculated for the synthesized images of the set,

and validating an approximate depth map calculated by iteration, as a function of the approximate depth z_app of 3D points of the corresponding model which relate to points I of the reference image, depending on whether it does or does not belong to the span ([z_m(i), z_M(i)]) calculated for these points I.

2. Process according to claim 1, wherein the calculation of the minimum and maximum values of the depth of a point I, for a synthesized image (4), is performed by utilizing an epipolar line corresponding to the point I in this synthesized image, to which are referred the distances corresponding to the maximum permitted distortion.

3. Process according to claim 1, wherein, the model is defined by a set of elementary regions, and the 3D points whose depth is utilized for the validating step are points of an elementary region of the model.

4. Process according to claim 3, wherein an elementary region is a facet and the calculation by iteration is a facetization of the depth maps, the iteration comprising creation of a new 3D facet vertex of the model or the deletion of a 3D facet vertex of the model depending on whether the process is of the “

coarse to fine”

or “

fine to coarse”

type.

5. Process according to claim 4, wherein if the process is of the “

coarse to fine”

type, the iteration comprises a calculation of the poorest approximate value from among the approximate values which relate to a facet and which are outside the spans, and the new vertex relates to a point corresponding to this value.

6. Process for compressing data defining a 3D scene, these data relating to reference images in respect of rendition and to associated depth maps, wherein the depth maps are modelled by facetization according to the process of claim 4 and the data relating to the reference images and to the depth maps are replaced with data defining the facets.

7. Process for compressing data defining a 3D scene, these data relating to reference images in respect of rendition and to associated depth maps, comprising the modelling steps according to the modelling process of claim 3, the elementary regions of the model being defined by a partitioning of the depth maps into image blocks, the calculation by iterations on an approximate depth map consisting of a modification of a quantization step size for these blocks so as to give a quantized depth which is the approximate depth.

8. Process according to claim 7, wherein the modification of the quantization step size is an increase in the quantization step size to obtain the widest quantization step size or the same quantized depth values for a block.

9. Process according to claim 1, wherein the set of synthesized images (4) on which the calculation of the errors is performed corresponds to a sample representative of the set of viewpoints using the reference image (7).

10. Process according to claim 9, wherein the set of synthesized images on which the calculation of the errors is performed is composed of images having a number greater than a threshold of 3D points in common with the reference image.

11. Process according to claim 1, wherein the maximum permitted distortion is predetermined as a function of a characteristic of an image.

12. Process according to claim 11, wherein a characteristic of an image is the luminance gradient.

13. Process for generating images, wherein the images are generated on the basis of a modelling of the scene according to the process of claim 1.