A rendering method of background reflections on a specular surface for CGH

Tsubasa Ichikawa
Hokkaido University, Japan

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Computer-generated holograms (CGHs) are remarked as ideal three-dimensional displays. CGHs are generated by calculating the light wave from the virtual objects in the computer. However, a lot of problems have to be overcome; such as the calculation takes an enormous amount of computation time, and rendering techniques are inadequate. We focused on the rendering techniques in order to reconstruct realistic images like in the field of the computer graphics. We have been proposed the calculation method for CGH that implements the hidden surface removal and the expression of metallic and refractive objects with the ray tracing method. In the previous study, we did not take into consideration the background reflection which renders reflected images mapped on metallic object’s surfaces. Reflected images are necessary to express complex realistic scenes. In this paper, we improved the previous work so that CGHs generates reconstructed images with background reflections. In proposed method, intersections between virtual objects and rays are calculated by the ray tracing method. Then intersections are assumed as a point light source group, and light waves on a hologram plane are calculated. In the ray tracing process, when a ray from a viewpoint hits the specular object, a ray is additionally casted to the specular direction from the intersection. If the ray hits other diffuse objects or background in the scene, the length of light path from a viewpoint to the diffuse object is calculated. By calculating light waves from a point light source on the diffuse surface distant from the light path in addition to a point light source on a specular surface, reflected images are expressed in CGH. To express the quality of materials, we adopted the Cook-Torrance reflection model. By optical reconstructions, it was confirmed that the reflected image with highlight was performed by proposed method.

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