Hello again and welcome back!
This week, we are going to talk about shooting at our target – be it a model, a patch of terrain or whatever you fancy. The post, albeit not very lengthy, is going to be a part of three short entries regarding how to shoot, process and bring into our modelling program the geometry we want to work with. Let’s begin!
First, and this is something that we have to keep in mind, we need to capture as much information of our target as we can. This circumstance will alter how we usually take pictures – it’s not about them being pretty, but sharp, focused and well oriented towards our model.
See how we circled around the beetle bench, taking shots at various angles and distances? This method ensures that most of the geometry will be visible to the camera, and that way we won’t lose any information. We’ve gone through this step in the ‘the road ahead’ blog post, but there’s some more important information that we need to cover as well in here. For instance, how does the sharpness of our pictures affect the overall quality of the model?
An obvious answer is that the less sharp an image is, the blurrier our final texture will be. Also, the software we will be relying upon is more likely to have a harder time processing all the data, since it tries to match similar points in space throughout different pictures. Here’s an example of two similar images with the same problem we’ve just talked about:
Now that we know how to approach our target – and how important a focused image is -, it is time to go through the position of our camera in regards to the model itself. Not only is it important to cover all the surface of the desired object, but how we aim towards it is also relevant. Let’s see what I mean with another example:
Let’s take a look at the images above.
/ The first picture is a general perspective of the whole model we want to photograph – it’s a sharp shot, which along many others taken at that same distance will contribute to give an overall idea of the bench. I’ve circled in red the part that I will be focusing on.
/ The second, third and fourth ones zoom in a little bit more towards the nose of the beetle bench. And this is the important bit. See how, even though they focus on the same area, the camera is aimed a little bit different for every single shot? The reason for this is that we want the faces of the model to be looking directly at us – that is, the normals of the surface should be pointing towards the camera. This will make both the tracking and the projection of the textures that much more accurate, and will make our life easier in the end.
Of course, sticking to these three principles will result in a lot of photos being taken – which is precisely what we need for better results. Don’t worry if you have to shoot anything between 400 and 600 pics, since that’s a normal number for a fairly complex model. There’s a lot of patience required in this process!
As a final piece of advice, and before we finish, there’s an extra step that we should be careful about that I haven’t mentioned yet… and that’s the weather. Whenever you want to head outside, plan in advance and see what the weather looks like. The best days are usually the cloudy ones, where there’s no sharp shadows and the images look very alike, no matter which angle you are shooting from. Sunny days, which are nicer by almost any other standard, can give you a harder time whenever you try to get your final colour texture – something that we’ll go over later on. Nevertheless, the worst case scenario is almost always the cloudy-but-not-so-cloudy day, when the sun decides to show up every now and then. Taking a lot of pictures under this weather will result in varying lighting conditions, which will most certainly destroy your colour textures and will stress your photogrammetry programs more than necessary. So plan in advance!
And with that being said, we’ll conclude this tour on how to take our images. Following this, we’ll take a look at how to process them in Agisoft, where we’ll get our model, our base texture and many other things in the future. Until then,
See you soon!
Brais Brenlla 