Tips and tricks

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Preview size

The size of the preview window can be controlled by adding previewsize mywidth, myheight; command to the header commands list. Default is 5000,5000 pixels which means it may sometimes fall out of your desktop (when you are rendering very big images). This can also take up some CPU time therefore it's wise to turn it to minimum when you don't need to see the preview. You can write

previewsize 10,10;

in the header line and it will only show 10x10 px render preview.

FG Transparency/Refractions

When you turn off FG Transparency/Refractions you will not receive any FG rays through transparent surfaces. This means that for example your windows will block FG rays and therefore the light will look inacurate.

So when you turn off FG transparency/refractions to speed up render make sure to move your glass to a separate layer object and turn ON "unseen by radiostiy" in the object properties.

Soft sun shadows

If you'd like to get realistic Sun soft shadows you don't need to use an Area light for it. Instead use a Spotlight and in the Kray "Quality" tab turn on "Spot to Area". Now to get accurate soft shadow angle it's best to set your Sun light 1km far away (you can do that quickly by adding SunSpot modifier) and then set your Spotlight Soft edge angle to 0.52°. This is because in reality the diameter of sun is about 0.52°. This way your sun shadows should look very realistic.

'include' command

When you have some header/tailer commands that you use often you can write them to a text file, one in each line, then you can add this command to the Kray header or tailer: include 'myfile.txt';

This will load all the commands you have written in that file. I'm attaching a file with commands I'm using. You can modify it to your liking....

renderinfosize 0.5,10; 
renderinfo "%kray %ver :: Rendertime: %hours h %mins min %secs sec:: rendersize: %width x %height";
logfile "kraylog.txt";

Uncached rendering

Whenever you want to get best quality render and don't care too much about render time you should use Uncached render (quasi Monte carlo - QMC).

You do that by turning "Irradiance caching" on the General tab off.


This will ignore all settings on the FG tab except FG threshold, min rays, max rays. What it does is it eliminates the calculation of sample points. Instead it will use every pixel as a sample point and will fire rays from each pixel.

This speeds up setup time because you don't need to deal with splotches and shadow quality.

Uncached irradiance will produce noise instead of splotches - it's similar to Fprime or LW radiosity, but still much faster.

You control the amount of grain by turning up Fg min/max rays.


Windows XP memory limit

Here's a tip if you have >2GB RAM installed on your machine. By default 32bit win xp will not use any RAM above 2GB. There is a way to force windows to use up to 3GB of physical RAM though. For this to work you need to edit boot.ini and add /3GB flag. Read more here.

This should allow rendering huge scenes and large output resolution.