In recent years, virtual reality technology has become a hotspot in computer vision, image processing, computer graphics, and artificial intelligence research. Virtual reality technology has also begun to be widely used, such as real estate, exhibition halls, entertainment and so on. Virtual reality based on image rendering technology is simpler and more efficient than traditional 3D modeling virtual reality method, and the constructed scene has high fidelity. The scene processing is only related to image resolution, and has nothing to do with scene complexity.
The ball screen projection technology uses virtual reality technology to create a 360-degree dome virtual scene. Since the content of the dome projection is to be fully displayed for a large viewing angle (more than 180 degrees). Therefore, the fisheye projection used in the dome system can produce a stereo immersion effect on the spherical surface, especially the virtual sphere. In computer graphics, fisheye projection usually has two cases, an orthogonal fisheye image and an isometric fisheye image, the former will cause stretching at the zenith and compression at the equator, while the latter can achieve pixel in The average distribution on the sphere.
The orthogonal fisheye projection is to project the points on the hemisphere parallel to the plane, and obtain a circular projection image on the image plane. The hemispherical projection range is up to 180 degrees. Near 0 degrees, the projected image is almost undistorted, but at the outermost edge of the plane (nearly 90 degrees), the image is very distorted, and the image in this place seems to be crowded. Due to this radioactive deformation of the orthogonal fisheye projection, the information loss at the edge of the dome is severe, so there is less projection in the practical application than the equidistant fisheye projection.
Isometric fisheye projection is defined as the distance from the point on the projected image to the center of the image and the angle at which the corresponding point on the sphere is connected to the optical axis of the camera to the optical axis of the camera. On the isometric fisheye projection image, the entire image distribution is almost uniform. The isometric fisheye projection range can be up to 360 degrees. However, the outermost edge of the 360-degree isometric fisheye projection image is projected onto the image plane near a point, so it is not easy to understand. It can be seen that the point-to-center distance on the projected image and the angle of the point on the projection sphere to the optical axis are directly mapped. Only one-half of the 180-degree isometric fisheye projection is projected onto the image plane, and 360 degrees can project all the scenes.
