Saturday 12 March 2016

Gestalt - 3D Modelling

The software programme Blender is often recommended as the best free 3D modelling software on the Internet.  I have long held an interest in trying my hand at 3D modelling and have downloaded Blender or other programmes in the hopes of giving it a go.  However, it's quickly evident when one opens these software programmes that a steep learning curve lies directly ahead!  Attempting 3D modelling from scratch is perhaps not for the faint-hearted.  But, last weekend I was determined to finally give it a try.  After watching a few excellent tutorials by Jacob Lewis (start HERE) I finally got off the starting blocks and managed to produce my first ever 3D model which I have affectionately called "Swifty".

The Inevitable Progression to 3D
Over the last year or so the subject of 3D modelling repeatedly crept into this blog under a number of guises.  It has started to dawn on me that this is going to be a valuable and necessary tool as this blog develops.  For instance, while trying to ascertain the direction of a light source on a subject in this posting HERE I came across a really interesting experiment performed by Prof. Hany Farid and his team from Dartmouth College.  They had generated a carefully constructed 3D world and 3D model in order to test theories about lighting and shadow.  More specifically they were testing a theory that a certain image showing a gun-toting Lee Harvey Oswald (Time Magazine cover Feb 21st, 1964) was a forgery.  This opened up the possibility in my mind of using 3D modelling and lighting environments to aid in bird identification from tricky photographs.  

The scientific value of 3D modelling is very neatly highlighted by an ongoing research project being undertaken in University of Sheffield.  The "Mark My Bird" project harnesses the power of citizen science to mark up and analyse the bills of all 10,000 bird species.  For more see HERE.  

3D modelling again came up while I was exploring the question of taking accurate 3D measurements from 2D images.  I used other open source software from the Internet to test a theory I had about a possible technique to make 3D models from 2D images - with some surprising results!  For more see HERE.

It was my most recent posting on the concept of Comparative Photographic Analysis (CPA) HERE that really sparked my interest in getting to grips with 3D modelling for once and for all.  By gathering together a collection of images of candidate species and making direct comparisons with our mystery subject it might be possible to glean some clues to it's identity.  Thats the premise behind CPA.  The next logical step following on from CPA would seem to me to be the generation of a 3D model.  With a 3D representation we might be able to actually replicate our photos using 2D renders from the 3D environment.  And that is what this posting is all about.

Meet 'Swifty' - my first 3D model
For my first effort I'm quite proud of 'Swifty', my first 3D model.  Through some structural modifications I can turn this model into a White-rumped Swift (Apus caffer), Pacific Swift (Apus pacificus) or any other Apus Swift.  Swifts make a pretty good subject for my first 3D effort, being fairly uniform in body structure, with fairly stiff wings.  This has allowed me to keep the number of 'moving parts' to a minimum.  While this is a fairly rudimentary design I don't need too much detail for the purposes of the experiment I am undertaking here.

Rough Versus Accurate 3D Modelling
Making 3D models from scratch is no different to any other form of art and design work.  Completed work may serve any number of functions.  A critically and painstakingly accurate, photo realistic 3D model might allow for the taking of very accurate measurements.  But the time and energy involved in making such a model might not be worth all the effort involved.  A model with that level of complexity would be more easily created using 3D scanning of real specimens rather than building a model from scratch.  However 3D modelling has uses at a more simple level.  We may be happy in some cases to work with a reasonably accurate representation like 'Swifty'.  If for example our goal is not to carefully measure the distance between two points but to test theories about structure and perspective, our simpler models might do the trick.  At least, that is my aspiration here.

The Dublin Bay Swift - another perspective
The purpose of my posting on a concept I call CPA (HERE) was to demonstrate how direct comparison between images can help generate clues about a bird's shape, or perhaps it's plumage field marks, to hopefully unlock a tricky identification.  In this posting I am approaching the problem from a different perspective - or rather, from infinite perspectives!  Here I have attempted to reproduce a number of Sture Persson's intriguing photographs by rendering 2D images of 'Swifty'.  The purpose is to try and understand what might be going on in each of the images.

Image 1
Above, once again I have presented a collage of the four key images photographed by Sture Persson.  Taking the left hand image first, one might initially assume this provides the best clues to the identification of this bird.  Afterall, it's a nice profile image.  However, as the CPA posting highlighted, this bird's wings are foreshortened in this image.  We really can't get any clues as to the length of this bird's wings from this image so I am not going to do any more with this image for now.

Image 2
The second image from the left is the sharpest.  What I find most intriguing about this (and the third image) is that the wings appear to be held in the forward-swept position.  For me this is key to trying to assess the length of this bird's wings relative to it's body.  In the examples below I have placed Swifty's wings in the forward position and tilted the bird slightly to match image 2.

Image 4
I have found this image particularly difficult to interpret.  Clearly the bird is flying at an angle somewhat towards the camera, but it's proportions appear odd from this perspective.  The key question is how much of the rump are we seeing in this image?  If we are mainly seeing the side of the rump then this would be inconsistent with A.caffer and more in line with A.pacificus.  However, just because a bird appears to be flying above head height does not rule out the possibility that the rump could be tilted down, towards the observer.  Perspective can play strange tricks on the brain.

Here is a short video demonstrating how Image 4 looks in this 3D model.  For more examples and a critique of 3D modelling and a related technique, CPA see HERE.

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