Limitations of Photogrammetry

While we do our utmost to create great 3D models for posting on this site, there are certain limits for photography-based 3D modelling, or photogrammetry. This Tachikoma (a character/vehicle in the hit anime series Ghost in the Shell) has been uploaded to underline this fact.

First and foremost, photogrammetry will not render (and forgive us for stating the obvious) anything not originally captured by the camera. This usually applies to the bottom of the model, so if you manipulate the object and look underside it, you will see only the “interior” of the model. There is a method of combining two picture sets; merging the top and bottom renders to form a complete whole, but this is a time consuming process and is grossly innacurate for those with sub-optimal equipment and poor technique.

Another limitation is how glossy surfaces confuse the rendering software, since how the light plays across the surface changes the “color”, at least for the non-intuitive eye of the camera. So the result is a mottled and rough surface for this model. For the same reason, fine details are lost.

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It’s hard to compete when you only have one camera and a cardboard box  XD

Photogrammetry software also has a hard time with models that have repeating features – in this case the phenomena is displayed in the claws of the rear left (when facing the Tachikoma) leg – one claw is displayed two times when you rotate your view around the leg.

tachikomaMissing
Where did it go??

Last are the unknowns – I swear I captured the rear portion of the model and rendered it properly, but it still disappeared in the final model. These kinds of errors usually stem from the actual photography process, and can probably be solved by taking a new set of shots – another 70-100 pics in other words.

Limitations are there to be solved or worked around however, and this technology is still wholly adequate for rendering other model types, such as the souvenir model of the Terracotta warrior on display here. This particular model came out great due to the model’s rough surface (non-shiny), lack of additional details at its bottom, and unique features.

Moving on, we will strive to put up even more models to illustrate this fascinating method of 360 degree viewing.

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