The primary goal of 3D digitizing is to obtain the (x,y,z) coordinates of feature points on the object to be digitized. To tell Photo4D what points on the object need to be measured, users need to mark the feature points in the images. This step is called marking and is done in the marking mode.
Marking is usually done by using the Mark page. A mark appear as an "X", or small hourglass in the Image windows.
If a feature point on the object appears in two or more images, one mark in each image should be used to capture this point. We say these marks are for the same point. It is absolutely essential for points to be marked in two or more images in order for Photo4D to compute their 3D locations. Remember, Photo4D cannot compute the (x,y,z) coordinates of a point unless it is marked in two or more images.
In Image windows, one point is always identified as the current point for which all its marks are highlighted in purple solid color (default). A point usually needs to be set as a current point in order to be edited.
In a project involving many points, marking should be done gradually. It is recommended to start by marking dozens of key points, then proceeding to the computation step (to be explained later), rather than marking all points at once. The iterative process makes it easier to find marking mistakes. See "Tips for Marking Image" for more details.
Users can change the default size or color of marks, if they are difficult to view in images. To do so use the [File|Configure...] menu in the Main Window.