Rayfront User Manual

Simulation Settings

This dialog configures the computational settings of each simulation. If you want to get more detailed control about the actual program parameters, you can press the Show Extended Settings-Button at the bottom of the dialog.

Basic Settings

Quality

This variable sets the overall rendering quality desired. It can have one of three values, Low, Medium or High. Most of the rendering options will be affected by this setting. The default value is Low.

Detail

This variable specifies the level of visual detail in this zone, and is used to determine image sampling rate, among other things. If there are few surfaces and simple shading, then this should be set to Low. For a zone with some furniture it might be set to Medium. If the space is very cluttered or contains a lot of geometric detail and textures, then it should be set to High. The default value is Medium.

Variability

This variable tells Rayfront how much light varies over the surfaces of this zone, and is used to determine what level of sampling is necessary in the indirect calculation. For an electric lighting system with uniform coverage, the value should be set to Low. For a space with spot lighting or a window with sky illumination only, it might be set to Medium. For a space with penetrating sunlight casting bright patches in a few places, it should be set to High. The default value is Low.

Indirect

This variable indicates how many diffuse reflections are important in the general lighting of this zone. A direct lighting system (eg. fluorescent troffers recessed in the ceiling) corresponds to an indirect level of None. An indirect lighting system (eg. hanging fluorescents directed at a reflective ceiling) corresponds to an indirect level of Low. A diffuse light shelf reflecting sunlight onto the ceiling would correspond to an indirect level of Medium. For full account of complex daylighting situations, High or even Extreme may be useful. The setting of this variable partially determines how many interreflections will be calculated. The default value is None.

Penumbras

This is a boolean variable indicating whether or not penumbras are desired. A value of True will result in penumbras (soft shadows), and a value of False will result in no penumbras (sharp shadows). Renderings generally proceed much faster without penumbras. The default value is False.

Zone Type

The "zone" specifies the volume of interest for this simulation. The type selection is either Interior or Exterior, depending on whether the scene is to be observed from the inside or the outside, respectively.

Zone Width/Length/Height

Those three values are the X, Y, and Z sizes of the bounding box of the "zone". It is important to set the zone dimensions correctly, as they are used to determine many of the rendering parameters.

The red, green and blue ambient value parameters depend on the setting of the zone type set, unless the Exposure Value below is set.

Exposure Value:

This value tells Rayfront how to adjust the exposure for display. It is important to set this variable properly as it is used to determine the ambient value. An appropriate setting may be discovered by running a preview and noting the exposure given by the "exposure =" command. The exposure setting may be given either as a multiplier or as a number of f-stop adjustments (eg. +2 or -1.5).

If no exposure is given, an average level will be computed by pfilt(1) and the ambient value will be set to 10 for exterior zones and 0.01 for interior zones.

Octree Size

This value is used to determine the proper setting for ambient resolution. This should be the length of the largest side of the bounding box around the total scene.

Other Settings

This section contains a few additional options, that control specific aspects of a simulation. Most of the time there will be no need to change anything here.

Image Oversampling: Automatic/1x/2x/3x

For high quality images, the first image can be rendered two or three times as large than the final size, and the raw file then gets filtered to the target size. The result is a smoother, antialiased picture, which is especially important when there was any direct sampling or direct jittering active. The Automatic position will determine the oversampling ratio depending on the Quality variable in the basic settings. The other positions force a specific oversampling ratio (or none for 1x).

Backfaces: Visible/Invisible

With this switch set to Invisible, back faces of opaque objects will be indeed invisible to all rays. This is dangerous unless the model was constructed such that all surface normals of opaque objects face outward. Although turning off back face visibility does not save much computation time under most circumstances, it may be useful as a tool for scene debugging, or for seeing through one-sided walls from the outside. This option has no effect on transparent or translucent materials.

Calculate: Radiance/Irradiance:

Switch for computing irradiance rather than radiance values. This only affects the final result in an image simulation, substituting a Lambertian surface and multiplying the radiance by pi. Glass and other transparent surfaces are ignored during this stage. Light sources still appear with their original radiance values, though the next option may be used to override this. This option is ignored for numerical simulations.

Light Sources: Visibile/Black:

Switch for light source visibility. With this option set to Black, sources will be black when viewed directly although they will still participate in the direct calculation. This setting may be desirable in conjunction with the option above, so that light sources do not appear in the output.

Pixel Aspect Ratio (optional)

Sets the pixel aspect ratio (height over width) to this value. Either the x or the y resolution will be reduced so that the pixels have this ratio for the specified view. If no value is set, then the x and y resolutions will adhere to the given maxima. This option is mainly of historical interest, since nowadays virtually all image displays use square pixels.

Pixel Sample Jitter (optional)

Set the pixel sample jitter to this value. Distributed ray-tracing performs anti-aliasing by randomly sampling over pixels. A value of one will randomly distribute samples over full pixels. A value of zero samples pixel centers only. A value between zero and one is usually best for low resolution images. If nothing is set here, then the default of 0.67 is used.

Extended Options

If you want to get more detailed control about the actual program parameters, you can press the Show Extended Settings-Button at the bottom of the dialog.

Buttonbar

Ok - use the entered values and close the dialog.

Cancel - discard the entered values and close the dialog.

Revert - discard the entered values and reset all fields to the values they had when the dialog opened.

Help... - display this information.

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