Process for modelling a 3D scene

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 zi 1 ) and maximum (z i +Δ zi 2 ) 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 zi 2 and on the minimum value of the error Δ zi 1 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 .