OpenGL-based Rendering of Computer-Generated Rainbow Hologram

For practical 3-D computer-generated holograms (CGH), it is important to display shaded surface model images like computer graphics (CG). However, to display shaded surface model images like CG, it is complex to use the Hidden Surface Removal Method (HSRM) in CGH, and necessary to write original shading program. Therefore, we have developed a simple process that is used to obtain 3-D data for CGH from two CG images. The first image is a shaded CG image. The second image is a depth-cued image, i.e., image intensity is modulated by the depth of the object. We use a z-buffer, which is usually used for HSRM, to make a depth-cued image. In order to render these two images, we have implemented our proposed method on OpenGL. However, OpenGL includes not only support for HSRM but also texture mapping, and alpha-blend. Therefore, in this paper, we show the effectiveness of the proposed method for texture mapping and alpha-blend. Moreover, since the previous method cannot render translucency by using alpha-blend, we have improved the previous method for rendering of translucent objects. In addition, we used a fringe printer, which we have developed as an output device of the hologram. In the result, we show the simulation of reconstructed images of computer-generated rainbow holograms from the processed 3-D data. We have also printed up to 3.2 Giga-pixels full-color rainbow holograms and evaluated optically reconstructed images.