This section provides an overview of the scientific contributions along with the corresponding publication history, since most of the results have been published in conference proceedings or scientific journals.
Depth estimation has been widely investigated, but we have added two contributions by adding smoothness constraints.
- Integration of a smoothness constraint for line consistency. We have proposed a smoothness constraint that enforces consistent depth between consecutive lines and we describe its integration into a simple one-dimensional optimization algorithm. This constitutes the first pass of the algorithm and results in one initial depth image for each view.
- Integration of a smoothness constraint for inter-view consistency. In a second pass, we have proposed a constraint that ensures consistent depth values across the views. This constraint is based on the re-projection of depth images (calculated at the first pass) onto the considered view as a means for improving the inter-view depth consistency. As a bonus, this re-projection method provides a simple solution for detecting noisy depth pixels.
The concept of integrating these smoothness constraints into a one-dimensional optimization algorithm was published in the Proceedings of the IEEE ICCE  and an elaborate description in the corresponding IEEE Transactions .
We propose two novel algorithms for rendering synthetic images using multiple depth and texture images.
- Novel formulation of the relief texture mapping. This novel specification has a formulation that matches with the geometry of multiple views. The proposed technique combines the two advantages of avoiding rendering artifacts (“holes”) in the synthetic image while simultaneously enabling an implementation on a standard Graphics Processor Unit architecture.
- Inverse mapping image rendering. We propose an inverse mapping rendering technique that allows a simple and accurate re-sampling of synthetic pixels. Additionally, the presented method provides a simple means for handling occlusions by an elegant, unambiguous construction of a single synthetic image from the two compositing neighboring views.
Preliminary results on image rendering were published in the Proceedings of the Symposium on Information Theory in the Benelux  and the new formulation of the relief texture rendering algorithm was published in the Proceedings of the SPIE SDA conference . The inverse mapping is a new unpublished result of which a publication is under development.
This part forms the most significant contribution of this thesis.
- Integration of a view-synthesis prediction algorithm into a multi-view depth and texture coder. The first contribution is the integration of an image rendering algorithm into a standardized H.264/MPEG-4 AVC video compression algorithm, to support predictive compression of multi-view video. We present a new coding tool that enables the compression of both multi-view texture images and also multi-view depth images. The rendering-based multi-view depth compression is completely new. This contribution has been published in the Proceedings of the IEEE ICIP  for texture multi-view coding and in the Proceedings of the SPIE SDA conference  for depth multi-view coding. Additionally, the impact of the view synthesis algorithm for predicting and encoding depth images was investigated and published in the Proceedings of the ACIVS conference .
- Depth coding with piecewise linear functions. The new algorithm models smooth regions in depth images with piecewise-linear functions and sharp edges by straight lines. Preliminary results were published in the Proceedings of 26th Symposium on Information Theory in the Benelux  and a fast method for estimating the model coefficients was published in the Proceedings of the SPIE VCIP conference . A rate-distortion optimization of the encoder was published in the Proceedings of the EUSIPCO conference . A complete description of the coding algorithm was published in the Proceedings of the SPIE SDA conference  and further improvements based on predictive coding of model coefficients were published in the Proceedings of the IEEE ICIP . Due to the work of the author on depth image compression, a cooperation with the Fraunhofer-Institute for Telecommunications Heinrich-Hertz-Institut of Berlin was initiated and resulted in two joint publications in the Proceedings of the IEEE Conference on 3D-TV  and in the journal on Signal Processing: Image Communication .
- Joint bit-allocation for depth and texture multi-view coding. A third contribution is a novel algorithm that concentrates on the joint compression of depth and texture images. Instead of the conventional separated optimization of texture and depth, the proposed algorithm considers for the first time a joint optimization of both the rate and the distortion so that an optimal rendering quality is obtained. This work was published in the Proceedings of the Picture Coding Symposium  and obtained a Best Paper award nomination.