From Kraytracing Wiki

Contents 1 General tab 2 Render preset 3 Save/Load 4 Diffuse model 4.1 Raytrace 4.2 Photon estimate 4.3 Photon mapping 4.4 Cache irradiance 4.5 Path tracing 4.6 Caustics 5 GI mode 5.1 Independent 5.2 Time interpolation 5.3 Shared for all frames 6 Camera 7 Pixel order 8 Iris Shape 9 DOF target 10 Output files 11 Tone map 12 Header cmds / Tailer cmds

General tab

Render preset

This selection list has all the predefined presets available to Kray. When a preset is chosen the corresponding values are used. For example: if you select Medium it will set “medium” preset for photons, FG, Quality and all the other “sub-presets”.

You can select between various presets we have defined to make work easier. Please keep in mind that while there was a lot of thought put into making the presets and they often are a good starting, they can't work in every situation an

Save/Load

Save buttons lets you save Kray settings into a file which can than be recalled in any scene by using Load button.

Diffuse model

This is the main render mode selection button. It lets you choose between various render methods which are explained below.

Raytrace

This mode will render the scene only with raytracing. This means that no global illumination will be computed. This mode is useful mainly for testing purposes. Make sure your raytrace flags are ON in Lightwave render globals to make it work properly.

Photon estimate

Photon estimate lets you choose between several modes that render out a quick representation of global illumination in the scene. In this modes no final gathering is used so rendering is very fast. Global filtered - mode renders photons that are fired into the scene and filters them.

Global unfiltered - mode renders representation of photons in the scene. You will sometimes want to see photon density in your scene and this mode is best for showing that.

Precomputed - will render out representation of irradiance cells. It mimics global illumination in a scene quite well. It's often used to see how big the cells in scene are and if irradiance is smooth enough or not.

Precomputed filtered – is very similar to precomputed. The only difference is that filtered mode filters (blurs) cells together. It renders very close representation of global illumination in the scene very fast and is therefore recommended mode to use when tweaking light or surfaces. This mode also offers option to ray trace shadows and render caustics which makes it even better representation of final render.

Photon mapping

This is the the main render mode in Kray render engine. It uses photon mapping with cached irradiance to render out full global illumination images fast.

Cache irradiance

When this check box is turned on Kray will use irradiance cache to speed-up rendering. Read more about irradiance caching here. When this check box is turned off Kray will not use any irradiance caching and will evaluate each pixel separately. This gives best quality shadows at the expense of render time.

Path tracing

Path tracing is a form of ray tracing whereby each ray is recursively traced along a path until it reaches a light emitting source where the light contribution along the path is calculated. This recursive tracing helps for solving the lighting equation more accurately than conventional ray tracing.

Caustics

The Caustics check box will enable rendering of caustics in the scene. So whenever you want caustics to show up, don't forget to turn this on.

GI mode

To speed up rendering of image sequences Kray offers 3 different modes.

Independent

This mode will turn off GI sharing. It's used for testing or when you're rendering a single still.

Time interpolation

This mode can be used whenever there are moving objects and/or light sources in a scene. Trick is Kray uses illumination data from current frame and from previously rendered frames. There are 2 basic ways of blending frames together. One is to take N previous frames and count its average illumination.

y0=(x0+x1+x2+...+xn)/N

where y0 is interpolation result for current frame x0 is irradiance computed for current frame, x1,x2,...xn are irradiances from previous frames. Number of frames N is controlled by Frames parameter in GUI.

Another way is to take interpolated solution from previous frame and blend it with current frame with given proportions.

y0=y1*e+(1-e)*x0

y1 is result of interpolation from previous frame, parameter e in equation is labeled Extinction in GUI.

You can combine both methods. Then interpolation equation will look as follows:

y0=y1*e+(1-e)*(x0+x1+x2+...+xn)/N

Interpolation can be applied to Precached map (photon/light map after precaching) and/or Irradiance cache (final gather cache)

Shared for all frames

If only camera is moving in your scene you should select this mode. You should specify a filename that Kray will use to save GI data into. If you don't specify any filename Kray will render into LightWave Image Viewer (only supported in LightWave 9.6+).

There are 3 different modes available:

Load: will load up the Gi data in the specified file. If the GI file doesn't contain enough data to accurately render global illumination it will compute new samples. This mode is often used when testing FG settings since it will only load save data and not save any new one into the file.

Save: will save computed GI data into the specified file when render frame is done.

Update: will load any existing GI data from file and on render end save new GI data into the same file. This mode speeds up rendering of animations dramatically. First frame will take some time to render, but all the consecutive frames will render much faster since they will compute GI only for the part of the scene that hasn't been calculated already. You should be careful with this mode when stopping and restarting rendering of animations. You should always use the same GI file to render complete animation. If you fail to do so you risk having sudden jump of light because every GI computation is a little different. So for example you rendered animation from frame 1-30 with one GI file and then frames 31-60 with another you will see a sudden jump of light in frame 31.

Reset File: Will clear the GI file on your disk so you don't have to go and manualy delete it.

Allow animation: will allow objects to move in the animation. Note however that GI will be computed only for first frame. Other frames will use existing GI. If you want to use full GI solution on animatable items use Time Interpolation mode

Camera

You can choose between using Lightwave camera or any of the built in cameras.

Lightwave: Will use currently selected Lightwave camera for rendering.

Spherical: Will render panoramic render mode, also called longitude/altitude. This is good for rendering out 360° panoramas.

Fisheye: panoramic render mode, also called light probe.

Texture baker: this mode allows to bake lighting on textures. Two options are available when this mode is selected. Object and UV name allows you to bake textures on object you want.

Pixel order

Pixel order allows user to select order of pixels appearing on screen. This option have influence on quality and rendering time if combined with Irradiance caching.

Scanline: will render pixels line by line starting at top.

Scancolumn: will render each row of pixels starting from left.

Random: will render pixels randomly.

Progressive: will progressively render the frame, updating image with better detail in each pass. This mode quickly shows a general preview of the lighting in the scene.

RenderWorm: will crawl through your image like a worm, revealing pixels underneath.

Frost: similar to RenderWorm but with a "frost" like effect.

Iris Shape

When DOF is enabled you can use any image to represent Lens aperture shape. This can be a simple black and white image of even color image so R, G and B rays all can have different iris shapes.

DOF target

will let you choose object which Kray will use as a focus point. This option overrides Lightwave camera Focal distance.

Output files

Lets you specify name of an output file where Kray will write the image to.

Format: You can choose between several standard file formats. HDR lets you render into high dynamic range image which enables you to tonemap in post.

You can use special symbols in filename to change its format. See renderinfo command for details.

Tone map

Tone mapping is used to apply color transformations on the final image colors. Sometimes an image can contain a higher range of colors that can be displayed on a computer screen. Color mapping has the task of re-mapping the image values to be suitable for display purposes.

Kray can use the following methods of tone mapping:

Linear: Will not apply and correction to the image (it's the same as using Gamma with parameter : 1 and exposure : 1). This may produce too dark images since images need some gamma correction to be displayed correctly on monitors. It's also what is used by Lightwave and Fprime by default.

Gamma: This is a standard correction. The amount of Gamma correction is defined by Parameter field. Most monitors use gamma correction of 2.2 but this may produce washed out images. Generally speaking values between 1.4 and 1.8 work best with Kray (if you want to use Linear Workflow, see Linear color space work flow in Kray), but feel free to experiment.

Generally you can think of the parameter value of something that affect contrast. Low values (for example 1) will have a lot of contrast and the dark areas will be really dark and possibly losing a lot of detail. A big value (say 2) will make the image have far less contrast and the dark areas will be more visible.

Exposure affects light intensity in general. It works similar to exposing photos. Higher number means longer exposure thus brighter image, lower shorter – darker image.

Another way to think of parameter and exposure is Exposure being the White point of the image and parameter the black point.

Exponential: will reduce the brightness of overexposed areas to pure white. Limits dynamic range of primary rays (those fired from camera). If a RGB component of a camera ray is bigger then value it is truncated. This is useful to make sure the overbright parts of an image are antialiased properly, for example the edges of polygons with Luminosity which is much higher than 100%.

LimitDR: by default limitdr is set to OFF (no dynamic range limit). LimitDR is done per camera ray, not per pixel. Therefore LimitDR command acts differently depending on when it's used. When its used before tonemap, Limitdr is applied before tone mapping and therefore any tonemaping like exposure or gamma can influence on how pixels are sampled (anti-aliased, etc.). When it's applied after tone mapping it will use current tonemapping settings for pixel sampling. Note that for Low Dynamic Range (LDR) images, it's dynamic range is always limited to output exposure.

HSV mode: when using tone mapping colors may loose their saturation. When this option is turned on Kray will try to keep saturation of colors instead of washing them out.

Header cmds / Tailer cmds

This are additional Kray “core” commands that do not have direct connection to buttons in GUI, but can instead be run by entering appropriate command.

You can find the list of all available commands here.