**5. Conclusions**

This review article has treated the main studies that have been carried out in recent years that use the projection mapping technique. Its purpose has been to provide the necessary help related to the calibration and lighting processes that may be required in future applications.

In the section on calibration techniques, different viable methods have been described to achieve the alignment between camera and projector, such as the structured light method [10,22], the beam splitter method [10], and the use of the Harris corner detector [24]. Furthermore, in many of the studies, different limitations have been taken into account, such as feedback, or the minimization of 4*E* in virtual restoration applications, proposing in both cases suitable solutions.

When using the projection mapping technique, attention must be paid to adequate lighting conditions, especially in those applications related to the exhibition and conservation of cultural heritage objects. For this reason, in the fourth section of this article, there have been reviewed the main lighting optimization studies whose aim is to minimize the change in appearance of the illuminated surface while reducing the harmful effects of radiation.

**Author Contributions:** Conceptualization, Á.G.M; Methodology, Á.G.M. and J.C.M.A.; Validation, Á.G.M, J.C.M.A. and A.J.B., Formal Analysis, Á.G.M; Investigation, Á.G.M; Data Curation, Á.G.M; Writing—Original Draft Preparation, Á.G.M; Writing—Review & Editing, J.C.M.A. and A.J.B.; Visualization, Á.G.M; Supervision, Á.G.M.; Project Administration, Á.G.M.; Funding Acquisition, Á.G.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work has been funded by project number RTI2018-097633-A-I00 of the Ministry of Science and Innovation of Spain, entitled 'Photonic restoration applied to cultural heritage: Application to Dali's painting: *Two Figures*.'

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
