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LIGHTING CONTROLS FOR SYNTHETIC IMAGES David R. Warn Computer Science Department General Motors Research Laboratories Warren, Michigan 48090 ABSTRACT The traditional point source light used for synthetic image generation provides no adjustments other than position, and this severely limits the effects that can be achieved. It can be difficult to highlight particular features of an object. This paper describes new lighting controls and techniques which can be to optimize lighting for synthetic images. These controls are based in part on observations of the lights in studio a professional photographer. Controls include a light direction to aim a at a particular area of an object, light concen- tration to simulate spotlights or floodlights, and flaps or cones to restrict the path of a light. Another control relates to the color of the and its effect on the perceived color of specular highlights. An object color blended with a highlights simulate different materials, paints, or lighting conditions. This can be accomplished dynamically while the image is displayed, using video lookup table approximate the specular color shift. CR Categories Subject Descriptors: 1.3.3 [Computer Graphics]: Picture/Image Generation - display algorithms; 1.3.7 Three-Dimensional Graphics Realism - color, shading, shadowing, and texture; Additional Key Words and Phrases: light controls INTRODUCTION The lighting model and controls described in this are part GMR AUTOCOLOR, a system developed General Motors Research Laboratories automatic generation of color synthetic images. The major application for Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. © ACM 0-89791-109-1/83/007/0013 $00.75 capability within GM is design evaluation, to view a realistic image prior to or in place of building a physical model in wood or clay. It can be used both to display automotive body surfaces to aid in their aesthetic evaluation display automotive parts constructed with the GMSolid [8] modeling aid visualizing complex geometric shapes. GMR AUTOCOLOR can also be coded scalar values such as stress [14], pressure, or curvature [ii] on surface of an object. The geometric shape of an object approximated by a mesh of three or four sided planar polygons. The polygonal representation was selected both for its availability within GM and for its efficiency. Polygons can be grouped to form parts. For a car body there might be separate parts for the door, hood, roof, fender, etc. Each part is assigned a surface type such as body or glass, and each type of surface has associated reflectance properties. entire data structure is stored tables REGIS interactive relational data base [12].
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This note was uploaded on 10/28/2010 for the course IT 25852 taught by Professor Daren during the Spring '10 term at Haaga - Helia University of Applied Sciences.


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