AuthorAaron F. Ross
Skill Level Intermediate
- [Instructor] If you're doing an architectural lighting study you're going to want to use photometrically accurate values for the lights and their color temperatures. And if you chose to use 3ds Max's exposure control then you could adjust the exposure of the camera in order to make the image the correct level of brightness. However, if you use 3ds Max's exposure control you're also succumbing to a destructive tone mapping effect that's being applied at render time. And you cannot remove that tone mapping in post. There really is no easy way to save out a raw image that's been exposure controlled and white balanced. If you're using another renderer other than Arnold then your best option is probably to multiply all of the light intensities by some value. Increasing or decreasing the overall amount of illumination is effectively the same as opening or closing the camera iris. There's not an easy solution for the white balancing issue. Let me show you. And if I do an ActiveShade rendering, I've got some photometrically accurate rectangle lights here if we go to the Modify panel. In the intensity color attenuation rollout you'll see I've got a Kelvin color temperature of 3,600, and intensity of 4,500 lumens which is in the approximate accurate range for this type of light fixture. And I've also got an environment map out the window, which is providing a bluer light. So if we're not going to use 3ds Max exposure control and we're going to render in some arbitrary renderer such as let's say Quicksilver, there's not really a solution for this, there's no way to color correct or white balance the camera itself. However, if you are using Arnold then you can apply an Arnold camera filter map which will allow you to adjust both the white balance and the exposure. And that's what we're going to see today. I'll select the camera in the scene, go over to the Modify panel. From the Modifier List, had an Arnold Properties modifier. And then open up the Camera section. And enable it. Then we can apply a filter map. So enable a filter map as well, click on the No Map button. In the Material Map Browser open up Maps and we can apply a Blackbody node. OSL provides a Blackbody node and Arnold does it as well. I prefer the OSL version because it performs a scaling after it normalizes the colors. We'll be able to adjust the exposure much more easily using the OSL map. So go into OSL, Utility, chose Blackbody, and click OK. If you want to edit that map we'll need to open up the Material Editor and drag it over into the view. Choose Instance, click OK, select the node and rename it. We'll call it env kelvin. And it looks like our ActiveShade hasn't really refreshed. So let's rerender ActiveShade. Now we see we've got a very extreme color temperature. With that map node selected go into the OSL Map Parameters, and set the minimum Kelvin value to 7,500 degrees, and the maximum to 7,500 degrees as well. And we've just basically applied a blue filter over our shot. Normalize is on so that the overall output is going to be constant regardless of the color temperature we choose. And then we also have an intensity which is a multiplier after the normalization. Set the intensity to a value of two, and we've basically opened up the iris or brightened up the filter. We can bring this up quite a bit, maybe a value of five, and we've really improved the quality there. Let's take another stab at the color temperature, maybe increase that a little bit more, and make some of these orange areas less orange. We'll set it to its maximum of 10,000 for a minimum and maximum, press Tab a couple of times, and type in 10,000, and that's as blue as we can make it. But we've pretty much done what we wanted. We've color corrected this shot and also changed the exposure and we've avoided using the built-in exposure control module and therefore we don't have to worry about any tone mapping that is introduced at render time. And if you want to take this a step further you can use a color node other than Blackbody as a filter map. For example you could use an OSL color value node, and plug in a color there, and then multiply it by some float value to increase or decrease its exposure. I'll leave that as an exercise for you. In this case all we needed to do was adjust the white balance and increase the exposure using the Arnold camera filter map.
3ds Max 2017: Advanced Lightingwith Aaron F. Ross2h 52m Advanced
3ds Max 2017: Advanced Materialswith Aaron F. Ross2h 34m Intermediate
3ds Max: Rendering with Arnold (2017)with Aaron F. Ross2h 40m Intermediate
3ds Max 2019 Essential Trainingwith Aaron F. Ross10h 39m Intermediate
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