|
|
| Line 25: |
Line 25: |
| RidgeRun implemented a GStreamer element that performs the equirectangular projection from an RGBA image. The element allows the adjustment of the projector setup through properties. The details of the element and how to use it can be found in section X. | | RidgeRun implemented a GStreamer element that performs the equirectangular projection from an RGBA image. The element allows the adjustment of the projector setup through properties. The details of the element and how to use it can be found in section X. |
|
| |
|
| == 360 Stitcher ==
| |
|
| |
| Finally, when you have the equirectangular image per camera, you can use RidgeRun’s cuda stitching solution to stitch them together. The purpose of the stitching is to align the equirectangular images, blending the overlap regions to produce a single 360 frame.
| |
|
| |
| The stitcher used for 360 frames generation is the same used for regular rectilinear stitching, the difference will be the type of input image and the configuration required for each case. As you may know, the stitcher supports putting together any amount of inputs, however for a 360 solution 2 or 3 fisheye cameras will be enough to cover the 360 world area around them. If your setup uses 2 cameras back to back it is recommended to use lenses of at least 190 degrees even though 180 degrees would be enough to cover the area. These 10 extra degrees allow the stitching to have a blending zone to work with, producing smoother transitions between the images. The overlap region will depend on your camera array configuration and the angles of view of the cameras you are using.
| |
|
| |
| To work with the stitcher you need to define a homography configuration, this is nothing else than a description of the relationship between the images. The homography configuration is defined in pairs of images, where one image is the reference and the other one is the target, the target will be transformed to match and adjust to the reference image using a homography matrix. In the case of fisheye 360 stitching, the projector already made most of the transformations required to match the images, and at this stage, only an offset definition will be required. For cameras aligned in the same plane, you only need to define the horizontal offset corresponding to the reference equirectangular image size minus the overlap region that will correspond to the angular distance between the cameras. In general, for 360 stitching your homography matrix will look like the following:
| |
|
| |
| [[File:translation-x-matrix.png|200px|thumb|center]]
| |
|
| |
| One of the challenges of stitching together 360 equirectangular videos is the parallax effect, which corresponds to the difference in the apparent position of an object viewed from different points of view and lines of sight. To have perfect stitching with no parallax effect your cameras should be in the same position which is physically impossible, so there cannot be perfect stitching in the real world. But you can adjust the projections and stitching configuration to have a nice blending at a certain depth, meaning a certain distance from the camera's array. However, if you adjust to some distance probably objects closer or further from that distance will present parallax issues. Also, the parallax will be determined by the distance between the cameras, smaller cameras closer together will be closer to the ideal setup where both cameras occupy the same space so the parallax effect is small but for bigger cameras further apart the parallax effect will be more noticeable.
| |
|
| |
|
| <noinclude> | | <noinclude> |
| {{Image_Stitching_for_NVIDIA_Jetson/Foot|Spherical_Video/About|Spherical_Video/Projector}} | | {{Image_Stitching_for_NVIDIA_Jetson/Foot|Spherical_Video/About|Spherical_Video/Projector}} |
| </noinclude> | | </noinclude> |