Lighting

In RealFlow there are three different ways to bring light into a scene: physical sky, IBL, and light emitters. The first two methods are adjusted globally under

Preferences > Preview > Maxwell Options

If you want to change the global/default settings for every scene individually go to

 Display shelf > Maxwell Preferences

Light emitter materials are available for every renderable node:

Selected node > Node Params > Maxwell Render > Material

Physical Sky

Here you are using the current time of the day for specifying the sun's/sky's colours. In the morning and evening hours you will see reddish and orange tones; close to noon the sky has a blueish appearance. Time is adjusted with the “Light” slider; under “Hour” you will see the appropriate time.

The sun's brightness is changed with “Global Intensity”, and if you want to keep a certain time of the day, but want to change shadow direction use the “Sun Rotation” slider.

Image Based Lighting (IBL)

When “Use IBL” is active “Use Physical Sky” is disabled simultaneously. Now you have access to four image slots for “Background”, “Illumination”, “Reflection”, and “Refraction”. Each channel can be configured separately, but it is also possible to use the background image globally with “Same as Background”. HDR and EXR files are supported.

Intensity

Adjust the HDR's brightness. Every slot has its own parameter, and with “Global Intensity” they can be adjusted at once.

Tile

Define the image's number of repetitions in horizontal and vertical direction.

Offset

Change the image's rotation in horizontal and vertical direction.

Light Emitters

Light emitters can coexist with any other illumination method, and every polygon node can be made a light source – there are three light-emitting materials:

Selected object > Node Params > Maxwell Render > Material > light_[...]

The object's size and resolution plays an important role here. If the object is

• too big you will see nothing more than a flat and dull disk, and there is almost no light emission
• very complex render time will increase drastically.

Another situation where lighting might fail is when the light source is not strong enough. Imagine a Hybrido fluid simulation in a big room, e.g. a subway station, and everything is lit with a handful of 25 W bulbs. In a scene like that you will hardly see any effect, and most of the subway station remains dark. Also if the sun's “Global Intensity” is very high it can outshine artificial light sources, and there is no visible additional illumination.