There is a natural desire to make the resulting 3D model to be as close to reality as possible. This can drive an assumption that more faces – the little triangles called polygons – are better and there is a direct correlation between poly count and detail.
A perfectly planar surface can be represented by just two triangles. Adding more faces will not change the accuracy of that representation.
We Don’t Live in a Planar World
A modernist and minimalist style can try to convince us otherwise but the world is not really planar. Definitely not in the world of shipwrecks at any rate. But this brings a problem; how can we display infinity detailed models that look and feel realistic when most consumers are using a smartphone?
We know through trial and error the iPhone 6s browser will fall over if we try and view a Sketchfab model with more than 1 million polygons. To cope with this we decimate the model down for display and in doing so drop some of the detail.
Frustrating? Certainly, but better than not sharing the model and if we are being honest Sketchfab does a great job casual viewing but has its limits not least of which are measuring or analysis tools.
Now there is help at hand. Both are worth exploring in their own right and both have differing use cases and outcomes.
Low Detail – No Problem
There is now a way to work with ultra low ploy count meshes whilst maintaining the appearance of massive detail. Agisoft Metashape now has the ability to create both normal and occlusion maps and we can exploit these to give the viewer of a model the feeling of more detail whilst at the same time using low poly counts. For this example we have used the Shetland wreck SS Gwladmena.
We have not even tried to publish a 45million poly model but two models are available to view on Sketchfab. Firstly, the higher resolution model with 6.4 million faces:
And now the low poly model with a mere 100,000 faces:
Massive Detail – No Problem?
The alternative approach is to decimate nothing and publish the 45 million faces. Now that would save messing around with decimation.
Recently we were contacted by Construked Reality to see if we were interested in doing just that? A look around the site showed some large georeferenced terrestrial sites being managed with apparent ease. But there was nothing from the underwater world akin to SS Gwladmena reprocessed. All those polygons were looking for a home why not upload that wreck and see?
Construcked will take texture wrapped OBJ files bundled up as a ZIP file. Not quite as slick as the Sketchfab interface but it can handle some massive files. Uploading georeferenced OBJ are not supported yet but position can be set using a single set of coordinates and viewing in context is a very useful feature for those inshore wrecks like the Gwladmena.
Here’s an embedded view of the wreck:
The model itself can be viewed here: SS Gwladmena on Construkted.com
One downside…the surface of the sea is a solid/no go area. For a wreck we would normally expect a negative value to represent depth below sea level but setting a negative depth hides the wreck. So for now setting a positive altitude means the wreck appears above the waves but it’s a minor detail as the viewer can handle the 45 million faces viewed in context plus there are measuring and position tools too.
The UB116 main site has recently been reprocessed to 47 million faces and has been upload:
The UB116 model itself can be viewed here: UB116 on Construkted.com
For the more serious user the interrogation tools – distance, area, points etc – do fill a gap Sketchfab seems to consistently overlook. For creators who prefer a representative shape then Sketchfab will suffice but for those needing more this site is worth checking out.
Do we have a Sketchfab killer? Its very early days but since acquiring more hardware I’m working through the back catalogue reprocessing work using the new tools Metashape gives us. I might stick things on High and let it run…now there is a viewing tool for just that.
Finally, if you want to go deeper into map types and how to deliver consistent quality models then do please take a moment to check out the Accupixel Metashape Standard online training course.
Accupixel are hosting the only course endorsed by Agisoft and their students are feeding back positive comments such as this:
” I’m really enjoying the course and I think you did beautiful work there.“
All of what we have discussed here is explored in far more detail than is possible in a blog.