Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I think that you could apply <a href="http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.163.250" rel="nofollow">space carving</a> in this instance (PDF can be downloaded from the link). This technique will allow you to construct a closed, polygonal representation of the subject.</p> <p>And, yes, some means of establishing the scale of your object will be needed. <a href="http://www.cse.unr.edu/~bebis/CS791E/Notes/CameraParameters.pdf" rel="nofollow">Here</a> is a brief discussion of the camera intrinsic and extrinsic parameters that are used to establish a relationship between an image pixel and an area (or volume). Since space carving requires that the viewpoint change between each frame, it's probably a good idea to recompute the external camera calibration parameters (extrinsic parameters) frequently. OpenCV has some capacity for determining camera parameters, see <a href="http://opencv.willowgarage.com/documentation/camera_calibration_and_3d_reconstruction.html" rel="nofollow">this reference</a> or perhaps this <a href="http://dasl.mem.drexel.edu/~noahKuntz/openCVTut10.html" rel="nofollow">tutorial</a>.</p> <p>Alteratively - if you can assume that the camera orientation will not change much between frames, you might try an easier method. As you suggested, an object of known size and orientation may be placed in the image, thereby providing scale cues. Note that this method is fairly straightforward, but will work under limited conditions. Foreshortening due to perspective and changes in perceived scale due to changing camera orientation will limit this method.</p> <p>Once the "space" of the chain has been identified and represented in polygonal (i.e. meshed) form, it should be straight-forward to compute the volume. OpenCV provides some mathematical primitives that should help.</p>
    singulars
    1. This table or related slice is empty.
    1. PODetermine the volume of an object from pictures
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USThrowback1986
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PODetermine the volume of an object from pictures
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. CO+1 thankyou for the info/links. Would a video sequence be easier to work with? What would be the difference between using HD video/SD video/HD pictures for the reconstruction?
      singulars
      1. PO
      1. USSimon
    2. COA video sequence could be helpful, but there are some things to be considered. Two adjacent video frames will probably not give you much to work with - the difference between them is not likely to be substantial. The rate of image capture and the rate at which the camera is moved around the scene will determine differences between frames. (Note that the camera may be moved or the object may be rotated within a still camera frame - they are more or less equivalent in this case). OTOH, optical flow techniques could speed identification of features in adjacent frames (reference object, etc).
      singulars
      1. PO
      1. USThrowback1986
    3. COHD versus SD is an interesting question. HD will give higher resolution, along with increased processing time. Many computer vision techniques begin with a filtering operation to attenuate unimportant signals (Gaussian blur, median filter, pyramidal downsampling, etc.). Thus, I try to start with the highest resolution image that makes sense in my constraints (time, memory, etc). If this were my problem, I would prototype in SD - verify my techniques, etc. If the result wasn't sufficient (i.e. my volume estimates weren't accurate enough), I would move up to HD.
      singulars
      1. PO
      1. USThrowback1986
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload