3D software allows an unprecedented control over how scenes can be lit. We describe recent software advances and the best current practices.
The analogy that we use elsewhere in this guide – that building a 3D model is like building a set for a movie – is particularly apt for describing the process of lighting. For the sample rendering of the house, we added a single light to the scene to simulate the sun – it’s floating about 200′ above the house like a gigantic stage light. The software we use, 3DS Max, allows us to modify some 80 parameters for any light we create – its color, the brightness, the angle of the shadows and how sharp, fuzzy or dark they are; it even allows us to selectively include or exclude whether objects are lit. If we needed a certain part of the rendering to be brighter, for example, all of the bushes in the front, we could simply create another light, adjust the parameters, and restrict that light to only include the bushes and nothing else. A 3D renderer thus has an enormous amount of control.
Under the Hood
No discussion of lighting a 3D model would be complete without mentioning the underlying software methods. This is a huge topic, so for the sake of limiting it to our focus here – 3D architectural visualizations – we will discuss the current, preferred method of lighting: global illumination, and contrast that with an older method of lighting called ambient illumination.
Global illumination simulates realistic lighting in a computer scene by rendering not only the light energy emanating from direct sources like the sun, or a desk lamp, (called “direct illumination”) but also takes into account light energy as it bounces off the other objects in the scene (called indirect illumination), for example the walls in a room. The underlying software used to calculate global illumination is extremely complex and requires a great deal of processing power. It is only recently, approximately in the last three to four years, that PC hardware has advanced to a level capable of supporting global illumination. Prior to these advances, most 3d architectural lighting relied on a simpler and less realistic rendering technique known as ambient illumination.
Ambient illumination takes into account only direct illumination, sources like the sun or a light bulb. Indirect illumination, the light energy bouncing of the other surfaces like walls is not calculated, but instead simulated with a “cheat” by specifying a generalized ambient illumination. Because indirect illumination is not calculated, this rendering method is much faster than global illumination. The disadvantage is that the shadows will appear flat and the overall image quality will be far less realistic. The difference between the two lighting methods is illustrated in Figure 8.1. On the left is the scene lit with global illumination, and on the right the same scene rendered with ambient illumination.
[Insert Figure 9.1]
So what does this all mean for 3D architectural visualizations? With global illumination, renderings can now achieve a level of lighting fidelity and subtle beauty that make them indistinguishable from actual photographs. Renderings can now also be highly accurate physical simulations of lighting design. Certain architectural projects require highly specified lighting – a prime example is an art gallery. The lighting and rendering software we use – V-Ray – allows us to import the lighting specifications for actual light fixtures, and we can thus create lights in our 3D scene that are 100% physically accurate. We have to be attentive that the rest of the scene be equally accurate, for example that the reflectivity of the materials on the walls, floors and ceiling be correct because this will determine how much the light energy is absorbed or passed on. If we accurately embed all of this information in the model, the resulting rendering will be a high fidelity image that documents the lighting design with great precision.
The other core concept to emphasize here is that if you employ the services of a 3D renderer, your image should be lit with global illumination. 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.
Creating Objective or Subjective Scenes with Lighting
Visualize, if you will, a continuum of 3D renderings. At one end of the continuum are what I term “objective” renderings. At the opposite end are “subjective” renderings. In their idealized state, objective renderings present a wholly factual summation of the design; they are meant to be cerebral and informative, like a witness in a courtroom “stating the truth and nothing but the truth”. By contrast, subjective renderings are meant to illicit an emotional response. They still impart factual information about the design, but artistic choices are made to heighten the dramatic impact of the image. Most all 3D renderings are a hybrid of these two typologies. Images presented to a city council for design review are generally on the objective end of the spectrum. Images created for a marketing campaign showing a couple enjoying the sunset view from their new balcony are at the subjective end of the spectrum.
Lighting is one of the principle actors that create either a subjective or objective rendering. If we’re creating an objective exterior rendering, our studio usually creates a light to represent the sun on a clear cloudless summer day at about 11:00 am. The overall lighting of the scene is neither over nor under exposed and the shadow angles are crisp and allow a clear ‘reading’ of a design’s full three dimensions.