| authors |
Sawicki, Bogumil |
| year |
1995 |
| title |
Ray Tracing – New Chances, Possibilities and Limitations in AutoCAD |
| source |
CAD Space [Proceedings of the III International Conference Computer in Architectural Design] Bialystock 27-29 April 1995, pp. 121-136 |
| summary |
Realistic image synthesis is nowadays widely used in engineering applications. Some of these applications, such as architectural, interior, lighting and industrial design demand accurate visualization of non-existent scenes as they would look to us, when built in reality. This can only be archived by using physically based models of light interaction with surfaces, and simulating propagation of light through an environment. Ray tracing is one of the most powerful techniques used in computer graphics, which can produce such very realistic images. Ray tracing algorithm follows the paths of light rays backwards from observer into the scene. It is very time consuming process and as such one could not be developed until proper computers appeared, In recent years the technological improvements in computer industry brought more powerful machines with bigger storage capacities and better graphic devices. Owing to increasing these hardware capabilities successful implementation of ray tracing in different CAD software became possible also on PC machines. Ray tracing in AutoCAD r.12 - the most popular CAD package in the world - is the best of that example. AccuRender and AutoVision are an AutoCAD Development System (ADS) applications that use ray tracing to create photorealistic images from 3D AutoCAD models. These ,internal"' applications let users generate synthetic images of threedimensional models and scenes entirely within AutoCAD space and show effects directly on main AutoCAD screen. Ray tracing algorithm accurately calculates and displays shadows, transparency, diffusion, reflection, and refraction from surface qualities of user-defined materials. The accurate modelling of light lets produce sophisticated effects and high-quality images, which these ray tracers always generates at 24-bit pixel depth,"providing 16,7 million colours. That results can be quite impressive for some architects and are almost acceptable for others but that coloured virtual world, which is presented by ray tracing in AutoCAD space in such convincing way, is still not exactly the same as the real world. Main limitations of realism are due to the nature of ray tracing method Classical ray tracing technique takes into account the effects of light reflection from neighbouring surfaces but, leaves out of account the ambient and global illumination arising out of complex interreflections in an environment. So models generated by ray tracing belong to an "ideal" world where real materials and environment can't find their right place. We complain about that fact and say that ray tracing shows us "too specular world", but (...) (...) there is anything better on the horizon? It should be concluded, that typical abilities of today's graphics software and hardware are far from exploited. As was observed in literature there have been various works carried along with the explicit intention of overcoming all these ray tracing limitations, These researches seem to be very promising and let us hope that their results will be seen in CAD applications soon. As it happens with modelling, perhaps the answer will come from a variety of techniques that can be combined together with ray tracing depending on the case we are dealing with. Therefore from the point of view of an architects that try to keep alive some interest on the nature of materials and their interaction with form, "ray tracing" seems to be right path of research and development that we can still a long way follow, From the point of view of the school, a critical assimilation of "ray tracing" processes is required and one that might help to determinate exactly their distortions and to indicate the correct way of its development and right place in CAAD education. I trust that ray tracing will become standard not only in AutoCAD but in all architectural space modelling CAD applications and will be established as a powerful and real tool for experimental researches in architectural design process. Will be the technological progress so significant in the nearest future as it is anticipated? |
| series |
plCAD |
| references |
Content-type: text/plain
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Foley, J.D. (1989)
 Fundamentals of interactive computer graphics
, Addison-Wesley, New York
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McNeel, Robert and Associates (1993)
AccuRender - Photo-realistic images inside AutoCAD
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Minnaert, M.G.J. (1993)
Light and Color in the Outdoors
, Springer-Verlag, New York
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Wojdala, A. (1992)
Ray-tracing: the state of the art
, IPI Machine Graphics & Vision, vol. 1,nos. 1/2, 1992, pp.108-155
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Wyvill, G., Ward, A. and Brown, T. (1987)
Sketches by Ray Tracing
, Computer Graphics 1987, Proceedings of CG International Conference. Springer-Verlag, Tokio
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| last changed |
2000/01/24 10:08 |
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