In the last sections we have been looking at a bit of the theory concerning 3D Reconstruction. Hopefully we have set the foundations for discussion in site presentation and interpretation that we will return to in further sections. It is however time to start talking about one of the most commonly used programs for reconstruction, Google SketchUp.
The first question is why SketchUp. Out of all the software that is available, I think this is the easiest to learn. Programs such as 3Ds Max have many advantages that set them aside, yet for all the limitations SketchUp may have it is perfect for those who have little knowledge of modelling software. The range of tools is enough to create fairly accurate models, and combining it with V-Ray produces good quality 2D renders. Additionally, the interface is intuitive. The only elements I would criticise are rounded surfaces and textures, which are much harder to work with and may require additional software such as Photoshop.
For navigation, Google Sketchup utilises a combination of a panning, a rotating and a zooming tool. These are used to move around the scene without interfering with the model itself. Similarly, a moving, a rotating and a scaling tool allows manipulation of an object in the scene. The main feature to use though is the push/pull tool, that allows simple surfaces to become three dimensional elements.
When modelling a site, I tend to start from a plan. It is in fact much easier to start from the ground surface upwards. you can easily drag and drop a plan into the scene. If you want the model to be to scale, the plan itself can be adjusted by using the measuring and scaling tools accordingly. Once the plan is in place it is possible to trace over all major features, to start creating a floor plan of site. The ‘pencil’ can be used to trace over most lines, but the rectangle, circle and arc tools are also essential for some portions of the plans.Curved surfaces cause some issues with the software, so I would tend to use smaller straight lines whenever possible.
Once the plan is sketched out, it is time to push and pull surfaces. With any luck, the surfaces should have closed automatically, by finishing off every line at the same point it started. In some cases the line tends to snap to the axis, so beware if it becomes a certain colour before clicking. The push/pull tool allows you to extend the selected surface outward or inwards, and it can be used to give objects height or depth. In the bottom corner SketchUp informs you on the distance that the surface is being extended, so it is possible to apply precise calculations. Most of the reconstruction process involves drawing surfaces upon other surfaces and pulling/pushing them to create the details of the model.
One of the functions however that I find the most useful is the ‘component’ tool, which divides different elements into compact objects that don’t interfere with one another. Often pulling a surface over another can cause the two to become conjoined, making it difficult to modify the specific part after the initial modelling. By selecting a single entity in the model (for example, a table) and making it into a component you can then move it freely without worrying about the rest of the model, as well as copying it without having to remodel it. Ideally, every different part of the reconstruction should be its own component, part of a hierarchy. Larger components are themselves composed of smaller components, so that it is possible to operate at many different levels. Using components efficiently also simplifies the transition between SketchUp and Unity3D. Bear in mind however that components that have been copied will maintain a connection with the original, and any change that is applied to a single ‘instance’ of a component will also be applied to all other copies.
In the next part I will continue the discussion regarding Google SketchUp modelling to incorporate detail building, rendering and materials.