Global Illumination.

BusyRay uses algorithm called bi-directional path tracing. Strength of this algorithm is that it can accurately simulate arbitrary materials (no matter how diffuse or glossy) and arbitrary light sources. No special changes in the scene are needed to enable the global illumination. Just choose BusyRay as your current 3DS MAX renderer and render your existing scenes - global illumination should appear automatically.

Accuracy estimation.

BusyRay estimates accuracy per-pixel during the computation. Computation continues as long as there is at least one pixel with error larger than specified threshold. Desired accuracy is specified using this dialog:

The unit of error estimation is one level of display brightness (i.e. error can vary from 0 to 256). The smaller "Wanted" error, the better quality you will get, but the longer time you will have to wait while the image is ready. If you need just a draft image, set error to 256. Image with moderate quality will be computed at default error level equal to 5. If you need a noiseless image, or if you are computing an animation, we recommend to set "Wanted" error to 3.

Specular reflection.

BusyRay supports reflection by standard Raytrace materials included into 3DS MAX. Reflection is controlled by 'Reflect' parameter of the below dialog. Fresnel reflection can be enabled by switching between different options of that parameter.

Glossy Reflection.

One can get glossy reflection with any material (not necessarily Raytrace). In principle any material (even diffuse) creates blurry reflection, but it might be not noticeable if it is TOO blurry. To make glossy reflections visible, one has to make the glossy peak narrow and high as shown on Figure below. Closer objects create sharper reflections, farther objects create reflections that are more blurry.

Area light sources & Soft shadows.
There are two ways to get soft shadows in BusyRay. One of them is to use "Area Shadows" setting of standard 3DS MAX lights. Below we show how one creates omni rectangular light 10x10 cm. This kind of light would cast soft shadows when used with BusyRay. The larger light source size - the more blurred shadow borders will be.

Another way to create an area light source is to assign self illumination to material. For example, here is the setting of red emitting Blinn material (Self-Illumination parameter is set to 50):

Or gray emitting Raytrace material (Self-Illum parameter is set to 50):

Editing of tone mapping parameters

Tone mapping determines how high dynamic range (HDR) values are mapped to low dynamic range of monitor. Parameters that define this mapping are MinHDR/MaxHDR and tone mapping curve. MinHDR/MaxHDR define interval of physical values that will be mapped to sensible colors on the screen. All physical values that are smaller than MinHDR will be mapped to black and all physical values that are larger than MaxHDR will be mapped to white. In-between HDR values will be mapped according to the tone mapping curve. Using dialog depicted below BusyRay allows to choose one of the common curves: 'Line', 'Gamma', 'S-shape'. Parameters of 'Gamma' and 'S-shape' curves can be adjusted using slider to the right from the curve selection list box. By selecting 'Custom', curve can be edited directly using mouse. In this mode double click with the left mouse button introduces new curve control point, click with the right mouse button removes curve control point. If 'From Scene' curve is selected, BusyRay will build automatic curve basing on preview rendering of your scene. 'Auto Min/Max' checkbox enables automatic selection of MinHDR/MaxHDR basing on preview rendering of your scene.

High Dynamic Range channel output

BusyRay performs all computations in physical units. Before display, these values are tonemapped and clamped to fit low dynamic range of the monitor. Sometimes it can be of interest to see what were the original non-clamped floating point values. To see these values, press 'HDR channel' checkbox in the BusyRay rendering dialog (below).

After rendering HDR values can be picked in framebuffer using right mouse button (Non-Clamped Color values on Figure below):