Arrow Group Industries LM86 Manual do Utilizador descarregar pdf (Página 30)

Maxwell Render 2.5 User Manual

Chapter 7. Setting up environment lighting | 30

F.01 Default settings (0.04) F.02 Turbidity 0.65, Scatt. Asymmetry 0.7 F.03 Turbidity 0.65, Scatt. Asymmetry -0.7

Note: Very high Turbidity Coefcient values such as 0.5 are also possible for very dense

aerosol atmospheres, for example after a volcano eruption.

• Wavelength Exponent: Denes the average size of the particles in the atmosphere.

The particle size inuences which wavelengths of light are absorbed and which are

scattered. You can greatly vary the coloration of the sky by changing this parameter,

and the effect of the Wavelength Exponent will be more visible the higher you set the

Turbidity Coefcient. Having a lower value than the default 1.2 will have a desaturating

effect on the sky. Higher values than the default will at rst increase the saturation of

the sky, until gradually turning towards green and then orange:

F.01 Default settings (Wavelenght Ex. 1.2) F.02 Wavelenght Ex. 10 F.03 Wavelenght Ex. 30

• Reectance: Refers to the albedo of the aerosols, or the rate of energy scattered

and absorbed by the aerosols. Higher values will scatter more light from the aerosols

which will brighten the sky and scene illumination. Values range from 0 to 1. A value of

1 means that all light that interacts with the aerosols scatters, and none is attenuated.

• Asymmetry: This factor controls the anisotropy of the particles, that is, in which

direction most of the light will be scattered. Light can be scattered along the same

direction as the incoming sunlight (positive values), or back towards the direction of

the sun (negative values). A value of 0 means that the light is scattered equally in

all directions (isotropic value). Positive values will produce a halo effect around the

sun, brightening the area around it. Negative Scattering Asymmetry values will have

an overall darkening effect on the sky. Avoid setting a higher negative or positive

Asymmetry setting than -0.85/ 0.85 as this will result in noisier renders.

Tips for working with the Physical Sky:

• Keep in mind that the atmosphere parameters inuence each other. For example,

if you raise the Turbidity Coefcient (more particles in the atmosphere), the

Wavelength Exponent, Reectance and Scattering Asymmetry parameters will

then have a greater inuence on the look of the sky: they are affecting a larger

amount of particles.

• To keep the horizon from turning too bright, lower the Planet Reectance and

decrease the Scattering Asymmetry.

• Maxwell Studio and some of the plug-ins can interactively show an accurate

OpenGL view of the current sky coloration and brightness. In Studio, press the

“K” key to activate/ deactivate the Sky Preview. This OpenGL view also takes

into account the cameras’ f-Stop, ISO and Shutter Speed settings.

• The scene illumination and coloring change depending on what sky settings

you use. If you raise the ozone level, which makes the sky scatter more blue

light, your entire scene will have a bluer illumination.

• Because the Maxwell camera has a xed white balance of 6500K, you can

save your render in any of the HDR (High Dynamic Range) formats available,

such as tiff32, .EXR, .HDR, and white balance your image in an image editing

application that can handle HDR les.

7.04 Image Based Lighting (IBL)

Image Based Lighting allows you to light your scene by applying an HDR image to a virtual

sphere that encompasses your scene. This is useful if you want your 3D model to appear

as if it is actually in a real environment. The scene will be lit according to the properties of

the HDR image and reections from this environment will also show on your models. You

can use an .HDR, .MXI or .EXR image for the IBL. These three image formats store high

dynamic range data, providing accurate environment lighting. Please note that the images

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Arrow Group Industries LM86 Manual do Utilizador Página 30

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