3D Graphics with OpenGL ES and M3G- P11:Mobile phones are the new vehicle for bringing interactive graphics technologies to consumers. Graphics that in the 1980s was only seen in industrial flight simulators and at the turn of the millennium in desktop PCs and game consoles is now in the hands of billions of people. This book is about the technology underpinnings of mobile threedimensional graphics, the newest and most rapidly advancing area of computer graphics. | 84 LOW-LEVEL RENDERING CHAPTER 3 in the illumination either to vertex colors or to texture maps. This is done so that the environment and the light sources are modeled and then rendered using a high-quality but perhaps non-real-time method such as raytracing or radiosity calculations. One could even take photographs of real environments or model environments with real lighting and use those as texture maps. The illuminated surfaces are then copied to the texture maps which are used in the real-time application. Below we describe various approaches of using texture maps to provide advanced lighting effects. Figure illustrates several of them. From top left the first image shows dot3 bump mapping that gives an illusion of higher geometric detail on the barrel and walls that are affected by the main light source. The next image shows a projective spot light Figure Several passes of a scene bump mapping projective lighting using the circular light map on left middle adding environment map reflection to the barrel the cube map at left bottom adding shadows final image. Image copyright AMD. See the color plate. SECTION RASTERIZATION 85 using the light map on the left middle. Top right adds an environment map that reflects the light from the lamp from the surface of the barrel the environment map is shown at bottom left. The bottom middle image adds shadows and the last image shows the final image with all lighting effects combined. Light mapping Often you might want to reuse the same texture maps . a generic floor a wall panel or ceiling for different parts of your scene but those different areas have different lighting. Then you can use light maps that can usually be in a much lower resolution than the texture map. The light maps are used to attenuate the texture maps for white light or modulate them for colored light using multitexturing. The advantage over baking in is the potential savings in storage space and the possibility of having more dynamic .
