Rendering with mental ray and 3ds Max they may change much more than meets the eye. The color of the light is also somewhat pink, thus changing the overall look of the scene (see Figure 3.14). 8. If you look in the Exposure Control rollout, you'll also notice that the Shutter Speed has been sent back to its previous value. Enter 1 in the Shutter Speed numeric field and render again. The shutter speed value should be lower than what you set before because the lights are much less intense now. Again, use caution with presets because using them is sometimes like starting over again! Close all windows and dialogs and save the file. Photometric lights have parameters that allow you to simulate lighting in the real world more precisely. Parameters for intensity, for example, are based on wattage or candelas that can help establish a somewhat logical starting point for future adjustments. As you've seen, some of the presets provided try to match typical real-world lights. However, you've also seen that it is very difficult to know exactly what changes are made by those presets; they may directly affect not only the lights, but also the Exposure Control and more. If you are going to use the presets in production, make sure that you choose them immediately after creating your lights and before making any adjustments to the rendering. 3.4 SkyPortal We mentioned in the introduction to this chapter that mental ray is like a creature that needs to be fed a steady supply of energy in the form of photons emitted from light sources you place in a scene. Earlier, you placed a Daylight system in the scene to simulate the sun, and you had to make adjustments to compensate for the extreme energy produced by the sun. This energy from the sun, again in the form of photons, is emitted in all directions from the light source. A common scenario in 3ds Max is an interior scene with sunlight streaming through a window providing the only source of light for mental ray to render. If you look back at the analogy of feeding a creature, this would be similar to trying to feed the creature by throwing shovels' full of food in all directions. Some of that food may find its way into the creature's mouth, but much of it is just thrown off into space and wasted. 3.4.1 ChannelingdaylightwithaSkyPortal Sky Portal is a type of 3ds Max/mental ray object that channels the energy from the Daylight system into an area described by the size of the Sky Portal. The result is much less wasted energy and would be similar to feeding your creature with a spoon--nice and clean and efficient. Figure 3.14 Usingpresetsin 3ds Max can result in many changesthataredifficulttotrack andcontrol. The Sky Portal is not the source of light, a focusing device to reduce the overhead calculated by the computer. Let's look at a scene of a child's playroom with light coming through a window on the left side. 60