This bar contains two icons: the first one provides all relevant settings for adjusting the current Maxwell preview. A click on the second symbol opens the “Maxwell Interactive” window. If you want to change the default settings for the Maxwell render engine, please go to RealFlow's “Preferences” panel. All settings made here will only be valid for the currently active scene. The “Fire” button opens the “Maxwell Interactive” window where you will see the rendered view.

This icon bar is not part of RealFlow's default layout. To open it, please right-click on the icon bar and choose "Maxwell" from the appearing menu.

Maxwell Scene Preferences

Here you can find everything you need to adjust a Maxwell preview.

Illumination

Intensity

This value is used to adjust the “brightness” of the sky and works like a multiplier. A higher value adds more light to the scene, lower settings result in a darker impression.

Physical Sky

RealFlow's Maxwell integration provides two global illumination models: with “Physical Sky”, Maxwell creates a physically accurate model of a sky depending on the adjusted location and time. With this sky model it is possible to simulate conditions like sunrise, dawn or sunny summer days. When this option is inactive, a conventional sky dome model will be used instead.

Light

In the real world, the sky's colour and brightness depends on the current time. In the morning and evening hours, the colours have a high ratio of red and yellow. Around noon, the colour tends to be blue or white. The exact simulation of these colours is one of Maxwell's key features and produces absolutely realistic lighting scenarios. With the “Light” slider you can easily determine the current sky colour by dragging it to the desired time of day – from dawn to dusk.

Hour

This read-only field is a directly connected link to the “Light” slider and shows the corresponding time to the slider position.

Use IBL

When this option is checked the image-based lighting settings below will be accessible. The “Use physical sky” button will be deactivated simultaneously. As a consequence, you are no longer able to define the current time of the day with the slider, because all lighting information is now gathered from HDR images. The slots below “Use IBL” allow you to load different images for the render's background, illumination, reflection, and refraction channels.

IBL Channels (Background, Illumination, Reflection, Refraction)

These four tabs provide exactly the same parameters, settings, and buttons. “Background” specifies the image you will see in a render's background. With “Illumination” you are able to load an HDR image that acts like a global light source. An image under “Reflection” will be reflected on objects. This channel assumes that the object's material has some reflective properties. “Refraction” works similar to the previous channel, but here the node's material must not be completely opaque and have at least a small amount of transparency.

At the moment, RealFlow only accepts images with the extension HDR. Other formats, e.g. EXR, are currently not supported.

Same as Background

This option is not available for the “Background” slot for obvious reasons. If you check this box, the background HDR will be used to create a consistent lighting situation and environment. When this feature is active you do not have to load the background image again to the appropriate “HDR File” slot(s).

HDR File

The empty field contains the path to the HDR image you want to use. You can either add a path manually or choose an image with the equal-named button and a file browser.

Intensity

If you want to brighten the HDR's lighting, simply increase this value. It works very similar to the “Global Intensity” field above. Sometimes, values of 10, 20, or more have to be used to get enough light.

Tile

With these parameters it is possible to create repetitions of the HDR in horizontal and vertical directions separately.

Offset

To rotate the HDR image around the horizontal and/or vertical axes, please enter appropriate values to the two fields.

Global

Image Quality

This value determines the quality level and resolution of the render engine. Higher settings yield better images, but also need more time. The range for this parameter is between 20% and 100%. Please note that “Quality” also influences the default pixel size of the render. When the value is too low, the render is blurred or receive a warning message that the task cannot be completed. A good value ranges between 60% and 80%. Although this parameter is named "Image Quality", it is actually a resolution value.

Number of Threads

On multi-core or multi-processor systems it is possible to exclusively reserve computation power for Maxwell. The mode of operation is actually the same as with “Threads” in the “Simulation” tab or the “Simulation Options”.

Global Scale

Because Maxwell Render uses real world units for lighting and camera settings, the size of your scene objects must also have a real world scale. For example if you wish to render a building, but that building was exported with a size of just 1 meter, it will be rendered it as if it were a miniature building, and the lighting will not match your intentions. These differences can be compensated with “Global Scale”.

Playback

Max Frame Time

If you want to limit the maximum render time per frame to a certain time, just enter the desired value here. The default value is 60 seconds. Please note that Maxwell will abort the render process after this time – even if the given “Sampling level” is not yet reached.

Max Sampling Level

Maxwell is an ‘unbiased render engine’ and uses this sampling level to reduce the amount of noise in an image. The higher the sampling level, the less noise the final image will have. The default value of 7 is suitable for most previews. Of course it is also possible to choose a higher value, but this will result in (much) longer simulation times.

Engine

Maxwell Render comes in two flavours: the preview engine (Draft) and a high-quality renderer for final images (Production). Here you can choose which type you want to use for your images.

Motion Blur Factor

Maxwell Render also support highly realistic motion blur. The value acts like a multiplier to stretch the blurs.

Channels

RealFlow's implementation of Maxwell Render lets you several channels with your render. If you want to activate this feature just switch the appropriate channel from “off” to the EXR image format. The channel data is only stored with a Maxwell preview (Playback > Maxwell preview). When you do s single render with the “FIRE” engine, channels will not be calculated.

Alpha

This image contains an Alpha mask that can be used for compositing purposes.

Motion

When this channel is active, RealFlow will write out a file with colour-coded motion vectors. These images are used to create motion blur effect in a post process.

Normals

If you want to visualize the normals please activate this channel.

Fire

This window is a 1:1 representation of the currently active viewport and the adjusted point of view. Each transformation of the viewport's perspective (zooming, panning, rotating) will be immediately performed in the render window as well. The rendered image is based on the settings you have chosen under “Maxwell Scene Preferences”.

When a RealFlow scene is rendered or previewed with Maxwell, it has to be translated into voxels first. The duration of this process strongly depends on the currently active scene's complexity and “MultiPoint” settings. The preparation of several millions of particle can easily take a few minutes. During this process you will see an orange progress bar directly in the “Maxwell Interaction” window with a label (“Voxelization”). The voxelization progress is not necessarily linear and you might observe that the progress bar stops for a while – this is absolutely normal.

Please bear in mind that some actions need a new voxelization, for example when new objects are added to scene or the number of particles has changed. Other changes (for example an increased image quality or a different tiling of RealWave surfaces) will also require a complete refresh. RealFlow will initiate the scene refresh automatically and you do not have to start it manually.

There are also some helpful shortcuts available:

Ctrl/Cmd + Alt + LMB: Force Maxwell to perform a new render with voxelization
Ctrl/Cmd + Alt + MMB: Force Maxwell to perform a new render without voxelization

The keyboard commands even work when the “Maxwell Interactive” window is inactive (in this case the Maxwell FIRE icon is yellow).

Send to Maxwell Command Line

This button provides a very easy and comfortable way to create Maxwell previews and render jobs via the command line application. The advantage is that you do not have to compile the render commands and path to the scene file manually. RealFlow prepares everything automatically and fires off the scene file to the NOGUI application. Please note that the scene requires a “Camera” node, because otherwise the render will fail.

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