Augmented Reality and Heritage

Recently I have been attempting to move closer to what I have coined embodied GIS (see this paper)- that is the ability to use and create conventional GIS software/data and then view it in the real world, in-situ and explore and move through that data and feedback those experiences. As is clear from the subject of this blog I am using Augmented Reality to achieve this aim, and therefore am using a combination of 3D modeling software (blender), gaming-engine software (Unity3D) and conventional GIS software (QGIS). Where possible I have been using Free and Open Source Software (FOSS), to keep costs low – but also to support the community and to show that pretty much anything is possible with a FOSS solution.

One of the main hurdles to overcome when trying to combine these approaches is to figure out the workflow between the 2D/2.5D GIS software, the 3D gaming-engine environment and then finally overlaying all of that information onto the real world. There are many points during the process when data integrity can be lost, resolution of the original data can be affected and decisions on data-loss have to be made. I hope that this blog post (and the subsequent howtos on the next stages of the process) will enable people to identify those points and also to step people through the process so you can do it with your own data.

The first step toward embodied GIS is to move from the GIS software into the gaming engine. There are many ways to do this, but I have used QGIS, some command line GDAL tools and then blender. Over the next few posts I will show how you import elevation data, import/place archaeological information and then view the finished data via the web and also in the landscape itself.

This first post presumes you have at least a working knowledge of GIS software/data.

First you will need a Digital Elevation Model of your landscape. I am using Leskernick Hill on Bodmin Moor as my case study. I have the Ordnance Survey’s Landform PROFILE product which is interpolated from contours at 1:10,000 – resulting in a digital DTM with a horizontal resolution of 10m. To be honest this is not really a great resolution for close-up placement of data, but it works fine as a skeleton for the basic landscape form. The data comes from the OS as a 32bit TIFF file – the import process can’t deal with the floating-point nature of the 32bit TIFF and therefore we need to convert the TIFF to a 16-bit TIFF using the gdal tools. To install GDAL on my Mac I use the KyngChaos Mac OSX Frameworks. Binaries for other platforms are available here. Once you have GDAL installed, running the following command will convert the 32bit to a 16bit TIFF –

gdal_translate -ot UInt16 leskernick_DTM.tif  leskernick_DTM_16.tif

This is the first stage where we are losing resolution of the original data. The conversion from a floating point raster to an integer-based raster means our vertical resolution is being rounded to the nearest whole number – effectively limiting us to a 1m vertical resolution minimum. This is not too much of a problem with the PROFILE data as the vertical resolution is already being interpolated from contour lines of between 10m and 5m intervals – however, it can lead to artificial terracing which we will tackle a bit later. It is a bit more of a problem with higher-resolution data (such as LiDAR data) as you will be losing actual recorded data values – however with the PROFILE data we are just losing the already interpolated values from the contours.

Once the TIFF is converted then you will need to setup a local grid within your GIS software. Unity doesn’t handle large game areas that well – and will start the gamespace at 0,0 – therefore when we import our data it makes things much easier if we also can import our data relative to a 0,0 coordinate origin then to real-world coordinates. This is much easier than it sounds – and just involves using a false easting and northing for your data. In my case I made a simple shapefile of a 10k x 10k square that covered my study area the bottom left coordinates of the square (in the Ordnance Survey GB coordinate system (EPSG:27700)) were 212500, 75000. This means that the coordinates of any data I import into Unity will need to have 212500 subtracted from their eastings and 75000 subtracted from their northings. We can either do this programmatically or ‘in our heads’ when placing objects on the Unity landscape (more on this later in the howtos). It is an advantage having a relatively small study area and also having data in a planar/projected map projection – as the conversion will not need to take account of projections of earth curvature (as it would in a geographic projection such as LatLongs).

Therefore, you can choose to reproject/spatially adjust all of your data using the false eastings and northings within your GIS software – which makes the import a little easier. Or you can do it on an individual layer dataset basis as and when you import into Unity (which is what I do).

Once you have sorted out the GIS side of things, you will need to import the raster into blender – and build the 3D landscape mesh. I’ll try and explain this step-by-step but it is worth finding your way around blender a little bit first (I recommend these tutorials). Also, please bear in mind you may have slightly different window set-up to mine, but hopefully you will be able to find your way around. Please feel free to ask any questions in the comments below.

1. Open up blender – you should see the default cube view. Delete the cube, by selecting it in the panel to the right – then press ‘X’ and click delete
2. Now we want to make sure our units are set to metres – do this by clicking the little scene icon in the right-hand panel and then scrolling down to the Units drop-down and click the Metric button.

   Changing units to metric

3. Now add a plane – using Shift+A Add->Mesh->Plane (or use the Add menu). This will create a Plane of 2mx2m. We want this Plane to be the size of our DEM (in world units) so change the dimensions to be the same, in my case I set X to be ’10km’ and Y to be ’10km’. If you don’t have the dimensions panel on the right, click the ‘N’ key to make it appear.

   Setting the Plane Dimensions

4. You will notice that your plane has disappeared off into the distance. We need to adjust the clipping values of our viewport. Scroll down the panel with the Dimensions in it until you see the View dropdown. You will see a little section called ‘Clip:’ – change the End value from 1km to say 12km. Now if you zoom out (pinch to zoom out on a trackpad or use the mouse scroll wheel) you will see your Plane in all its very flat glory.
5. Before we start the interesting bit of giving it some elevation – we need to make sure it is in the right place. Remember that we are using false eastings and northings, so we want the bottom corner of our Plane to be at 0,0,0. To do this first set the 3D cursor to 0,0,0 (in the right-hand panel just beneath where you set the viewport clip values). Now click the ‘Origin’ button in the left-hand Object Tools panel, and click Origin to 3D cursor (the shortcut Shift+Ctrl+Alt+C)
6. You will also want to make sure the bottom left of the Plane is at 0,0,0. As the origin handle of the Plane is in the middle, for a 10x10km DEM you will need to move the X 5km and the X 5km, by changing the location values in the right-hand properties panel. That should ensure your bottom left corner is sitting nicely at 0,0,0.

   Setting the location

7. Our Plane currently only has 1 face – meaning we are not going to be able to give it much depth. So now we need to subdivide the Plane to give it more faces – think of this a bit like the resolution of a raster – the more faces the more detailed the model will be (at the cost of file size!). Enter Edit Mode (by pressing Tab). You will see the menu change in the Left Panel – and it will give you a set of Mesh Tools.
8. Click the Subdivide button – you can choose how much you want to subdivde but I usually make it to be around the same resolution as my DEM. So for a 10k square with 10m resolution we will want a subdivided plane with approx 1,000,000 faces. In Blender terms the closest we can get is 1,048576 faces. This is a BIG mesh – so I would suggest that you do one at high resolution like this – and then also have a lower resolution one for using as the terrain [see the terrain howto – when written!].

   Subdividing the Plane

9. We now want to finally give the Plane some Z dimension. This is done using the Displace Modifier. First come out of Edit mode – by pressing TAB. Now apply a material to the Plane, by pressing the Material button on the far right panel and hitting the [+New] button.

   The Material and Texture Buttons

10. Now add a texture to the new material by hitting the Texture button and again hitting the [New+] button. Scroll down the options and change the Type to ‘Image or Movie’. Scroll down further and change the Mapping coordinates from Generated to UV. Now click the Open icon on the panel and browse to the 16bit Tiff you made earlier. The image will be blank in the preview – but don’t worry blender can still read it.

    Applying the Image Texture

11. Once you have applied the texture – click the Object Modifiers button and choose the Displace Modifier from the Add Modifiers dropdown.

    Object Modifiers Button

12. When you have the Displace Modifier options up choose the texture you made by clicking the little cross-hatched box in the Texture section and choosing ‘Texture’ from the dropdown. First change the Midlevel value to be ‘0m’. Depending on your DEM size you may start seeing some changes in your Plane already. However, you will probably need to do some experimentation with the strength (the amount of displacement). For my DEM the strength I needed was 65000.203. This is a bit of weird number – but you can check the dimensions of the plane as you change the strength (see screenshot) you want the z value to be as close as possible to 255m (this basically means you will get the full range of the elevation values as the 16bit Tiff has 255 colour values. These should map to real-world heights on import into Unity. You may want to do some checking of this later when in Unity).

    Changing the Strength

13. Hopefully by this stage your landscape should have appeared on your Plane and you can spin and zoom it around as much as you like…
14. At this stage you are going to want to save your file! Unity can take a .blend file natively, but let’s export it as an FBX – so we can insert it into Unity (or any 3D modelling program of your choice). Go to File->Export->Autodesk FBX and save it somewhere convenient.

Well done for getting this far! The final steps in this HowTo are simply inserting the FBX into Unity. This is very easy, but I will be presuming you have a bit of knowledge of Unity.

1. Open Unity and start a new project. Import whichever packages you like, but I would suggest that you import at least the ones I have shown here – as they will be helpful in later HowTos.

   Creating a new Unity Project

2. Now simply drag your newly created FBX into Unity.  If you have a large mesh the import will probably take quite a long time – for large meshes (greater than 65535 vertices) you will also need the latest version of Unity (>3.5.2) which will auto split the large mesh into separate meshes for you. Otherwise you will have to pre-split it within blender.
3. Drag the newly imported FBX into your Editor View and you will see it appear – again you can zoom and pan around, etc. Before it is in the right place, however, you will need to make sure it it the correct size and orientation. First change the scale of the import from 0.01 to 1 – by adjusting the Mesh Scale Factor. Don’t forget to scroll down a little bit and click the apply button. After hitting apply you will likely have to wait a bit for Unity to make the adjustments.

   The FBX in Unity

4. Finally you will need to rotate the object once it is in your hierarchy on the y axis by 180 (this is because Blender and Unity have different ideas of whether Z is up or forward).

   Set the Y rotation

5. You should then have a 1:1 scale model of your DEM within Unity – the coordinates and heights should match your GIS coordinates (don’t forget to adjust for the false eastings and northings). In my case the centre of my DEM within real-world space is 217500, 80000. The adjustment for the false eastings and northings would be performed as follows:-

actual_coord - false_coord = unity_coord
therefore 217500 - 212500 = 5000 and 80000 - 75000 = 5000
therefore the Unity Coordinates of the centre of the area = 5000,5000

To double-check it would be worth adding an empty GameObject at a prominent location in the landscape (say the top of a hill) and then checking that the Unity coordinates match the real-world coordinates after adjustment for the false values.

I hope that helps a few people, there are a couple of other tutorials using different 3D modelling software on this topic so it is worth checking them out too here and here and one for Blender here.

In the next HowTo I’ll be looking at the various different ways of getting vector GIS data into Unity and adding in different 3D models for different GIS layers so stayed tuned!