Hi,
We have been starting to test CC to see if it can be useful for us in our business. On this a couple of questions have came up:
1. Photogroups
Are there any advantages/disadvantages to have several photogroups, even if all pics have same properties? Let's say I have 1000 pics - will there be any difference (processing speed, quality) if I would split these pics into several photogroups?
2. Tiling
Sort of same question as above, but on tiling: Any difference on quality and/or processing time depending on selection of (level of) tiling? Should we try to have as few tiles as possible, or could it possibly be the opposite => that MANY tiles are preferable?
3. Tiling algorithm
We'be been a bit puzzled on what it is that actually "triggers" that tiling is necessary. Let me explain: Some models we've done have been from quite large amount of (hires) pics, resulting in NO need for tiling. Other models have been fewer pics, but still resulted in need of tiling. How come..?
4. Tie pointsIt is interesting to note/see the resulting number of calculated tie points after aerotriangulation. It can differ severly from (in principle) same set of pics (for example: Before/after balancing pic histograms). It can differ a factor two. But strangely enough, more tie points doesn't necessarily make a better model... So the question: How should one "interpret" the resulting no:s of tie points? Can any "conclusions" be made from the calculated number?
5. User tie points
It is possible to create user tie points. But why...? I mean, in what situation is that useful/necessary? In principle: Is there any reason why I should put the time to add some manual tie point to the [many thousands] that are created in the aerotriangulation? Could A FEW manual tie points make any major difference to the quality of the created model?
Thanks a lot in advance for answers/comments! :-)
Answer
ContextCapture will process the photos and automatically determine the photogroups based on the camera properties (image dimensions, sensor size, focal length etc.) Splitting the subdividing the photogroups any further will not improve the performance /quality. If images share the same optical properties it is recommended that they be left in a single photgroup.
Producing big tiles (and less numerous) tiles the processing will go slightly faster but you must be careful and take note of the expected RAM consumption
We’ve been a bit puzzled on what it is that actually "triggers" that tiling is necessary. Let me explain: Some models we've done have been from quite large amount of (hires) pics, resulting in NO need for tiling. Other models have been fewer pics, but still resulted in need of tiling. How come..?
This is dependent on the number of the images but also their size and resolution
4. Tie points It is interesting to note/see the resulting number of calculated tie points after aerotriangulation. It can differ severely from (in principle) same set of pics (for example: Before/after balancing pic histograms). It can differ a factor two. But strangely enough, more tie points doesn't necessarily make a better model... So the question: How should one "interpret" the resulting no:s of tie points? Can any "conclusions" be made from the calculated number?
Unless you notice a real lack of tie-point in the 3D-View, you shouldn’t be concerned about that as we go through a “denser” computation during reconstruction. You can also find some relevant explanations in the AT-report
There are cases where automatic tie points are required to stitch sub-parts of the dataset that would not be automatically aligned (huge scale difference, lack of overlap etc.). This is not needed in most cases. It can also be used to add positional or scale constraints
On question 5. I can add some answer myself, after doing some experiments:
My AT without manual tie points resulted in severe errors of the model. But after adding a few manual tie points, the model turned out correct. See pics below:
After:
When you added manual tie points and it fixed your model, did you add the tie points based on where the object of choice was actually in the image? Even if CC showed it being red or yellow as it didn't match with the other images? Or did you add them based on what CC thought it should be, hence the green. Not sure if I explained myself well enough.
How did you add manual user tie points? Can you walk me through how you know where to put the tie points? How many pictures do you put them in? When I look at the automatic tie points, I can't seem to find how they are related to one another. How do you go about adding your own manual tie points?
Hi Julianna,
As you maybe noticed, my questions were posted more than two years ago... So I simply cannot recall how I did this...
You can find information in user guide from page 67. Anyway you have to use as control point (but without coordinate). You have to recognize the same point in different photo (at least 3 user tie points must be defined in 4 images (2 measures in each component that you want to fuse). If you already had an aerotriangulation, if there is some problem when you put the user tie point will be yellow or red (because the fisrt aerotriangulation is not correct). After insert user tie point resubmit aerotriangulation. Now (if user tie point is enogh and correct) if you check user tie point will be showed green.