Rendering

Recent advances in software now allow architectural renderings to have a fidelity and sophistication once available only to movie studios – we describe the best current practices.

We are nearing the end of the image production process. We have built the model, textured, lit it, and added the entourage. We are ready to render the final image. At this juncture I must point out that we have already rendered the scene many times. We performed test renderings at every production milestone, constantly verifying that the image is on track. These interim renderings are usually performed at low to medium quality settings. The reason for this is to keep render times low, and to speed the progress of reviewing the images and correcting the 3D model. When it’s time to render a final, the image resolution is usually set quite high and the parameters that control the image quality are set high, and this results in long render times. This section is meant to provide an overview of issues such as image quality, and the balancing act that happens between budget, computer horse power and schedule. And ultimately the main objective of this section is to define the quality of rendering you should expect from a professional 3D renderer. In order to do this we need to discuss the recent history of computer rendering technologies.

Old versus New

Up until about 2005, most 3D architectural renderers used a rendering technique that was fast, efficient and reliable, but resulted in images which were rather flat and not very realistic. This method goes by various names and has variable flavors, but the underlying technique shared by all is called “direct illumination”. Direct illumination renders a scene by taking into account only direct sources of illumination, for example the sun, a light bulb or a candle. In the real world, the physics of light is immensely more complex. Light energy emanates from a direct source and then interacts with other objects in its path. These objects absorb some portion of the light and reflect the rest, creating what is termed “indirect illumination”. It’s the reason why a red wall in an otherwise white room will cast a bit of pink everywhere – see Figure 10.1.

[Insert Figure 11.1]

The problem with trying to approximate this more physically accurate solution is that it is very, very computationally intensive. Prior to about 2005, direct illumination was simply the only reasonable method available to get a job rendered on budget and on time. The portion of the light equation that was not calculated – indirect illumination – was substituted with a shortcut. A generalized “ambient illumination” was specified for the entire scene, and the resulting image was flat and uniform, especially in areas of shadow.

Around 2005, PC hardware became powerful enough, and software was written that was reliable enough, to handle the computational load required to render both direct and indirect illumination. This method is called “global illumination” and has revolutionized the quality of rendering that 3D architectural renderers can deliver.

The bottom line is this: a professional 3D renderer should deliver an image that is created with global illumination technology. The hardware, software and professional expertise have evolved to a level that this is the only method to be used to create professional renderings. Anything less is not acceptable.

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