CONSISTENTLY EDITING LIGHT FIELD DATA
The invention describes a method for applying a geometric warp to the light field capture of a 3D scene, consisting of several views of the scene taken from different viewpoints. The warp is specified as a set of (source point, target point) positional constraints on a subset of the views. These positional constraints are propagated to all the views and a warped image is generated for each view, in such a way that these warped images are geometrically consistent in 3D across the views.
1 . Method for consistently editing light field data,
the method comprising:
processing the light field data that comprise a plurality of calibrated 2D images of a 3D scene depicted from a set of 2D views, the set of 2D views comprising at least two reference views and at least one additional view,
processing at least one initial set of positional constraint parameters associated with the at least two reference views, each of the positional constraint parameters representing a transformation to be applied to a given point in an original 2D image of the 3D scene depicted from a corresponding view, among the at least two reference views, to warp said original 2D image, the positional constraint parameters comprising:
a 2D source location in the corresponding view, of the given point in the original 2D image of the 3D scene depicted from the corresponding view,
a 2D target location in the corresponding view, of the given point in a warped 2D image of the 3D scene depicted from the corresponding view, the method comprising:
determining for each of the positional constraint parameters associated with the at least two reference views, a 3D source location, in the 3D scene, of which the 2D source location is the projection into the corresponding view and a 3D target location, in the 3D scene, of which the 2D target location is the projection into the corresponding view,
determining an additional set of additional positional constraint parameters, associated with the at least one additional views, as a function of the 3D source location and the 3D target location, each of the additional positional constraint parameters representing a transformation to be applied to a given point in an original 2D image of the 3D scene depicted from a corresponding view, among the at least one additional view, to warp said original 2D image,
warping each of the 2D images of the 3D scene depicted from the set of 2D views, as a function of the positional constraint parameters associated with said 2D views, to obtain the edited light field data.
2 . The method of claim 1 , wherein said plurality of calibrated 2D images of the 3D scene is further depicted from a set of corresponding matrices of projection of the 3D scene for each of the 2D views.
3 . The method of claim 1 , wherein it comprises a prior step of inputting the at least one initial set of positional constraint parameters.
4 . The method of claim 1 , wherein it comprises determining, for each of the positional constraint parameters associated with the at least two reference views, a line in 3D space that projects on the 2D source location, and a line in 3D space that projects on the 2D target location, and determining said 3D source location and said 3D target location from said lines.
5 . The method of claim 4 , wherein each line is represented in Plücker coordinates as a pair of 3D vectors noted (d,m), and wherein determining the 3D source location (P i ), in the 3D scene, of which the 2D source location (p i j ) is the projection into the corresponding view (V j ), comprises solving the system of equations formed by the initial set of positional constraints (p i j ,q i j ), in the least squares sense:
{circumflex over (P)} i =Argmin P i Σ j ∥P i Λd i j −m i j ∥ 2 .
6 . The method of claim 1 , wherein warping implements a moving least square algorithm.
7 . The method of claim 1 , wherein warping implements a bounded biharmonic weights warping model defined as a function of a set of affine transforms, in which one affine transform is attached to each positional constraint.
8 . The method of claim 7 , wherein it comprises a prior step of inputting the affine transform for each positional constraint.
9 . The method of claim 7 , wherein it comprises a prior step of determining the affine transform for each positional constraint by least-squares fitting an affine transform at the location of the point, from all other the positional constraint parameters.
10 . The method of any of claim 1 , wherein it comprises rendering at least one of the warped 2D images of the 3D scene.
11 . An apparatus ( 1 ) for consistently editing light field data, in which:
the light field data comprise a plurality of calibrated 2D images of a 3D scene depicted from a set of 2D views, the set of 2D views comprising at least two reference views and at least one additional view,
at least one initial set of positional constraint parameters is associated with the at least two reference views, each of the positional constraint parameters representing a transformation to be applied to a given point in an original 2D image of the 3D scene depicted from a corresponding view, among the at least two reference views, to warp said original 2D image, the positional constraint parameters consisting of:
a 2D source location in the corresponding view, of the given point in the original 2D image of the 3D scene depicted from the corresponding view,
a 2D target location in the corresponding view, of the given point in a warped 2D image of the 3D scene depicted from the corresponding view,
said apparatus comprising a processor configured for:
determining for each of the positional constraint parameters associated with the at least two reference views, a 3D source location, in the 3D scene, of which the 2D source location is the projection into the corresponding view, and a 3D target location, in the 3D scene, of which the 2D target location is the projection into the corresponding view,
determining an additional set of additional positional constraint parameters, associated with the at least one additional views, as a function of the 3D source location and the 3D source location, each of the additional positional constraint parameters representing a transformation to be applied to a given point in an original 2D image of the 3D scene depicted from a corresponding view, among the at least one additional view, to warp said original 2D image,
warping each of the 2D images of the 3D scene depicted from the set of 2D views, as a function of the positional constraint parameters associated with said 2D views, to obtain the edited light field data.
12 . The apparatus of claim 11 , wherein it comprises a Human/Machine interface configured for inputting the at least one initial set of positional constraint parameters.
13 . The apparatus of claim 11 , comprising a displaying device to display at least one warped 2D image of the edited light field.
14 . The apparatus of claim 11 wherein said apparatus belongs to a set comprising a light field capture device.
15 . A computer program product downloadable from a communication network and/or recorded on a medium readable by a computer and/or executable by a processor, comprising program code instructions for implementing a method according to claim 1 .