Questions are raised all the time about Irradiance Map saving. Here are the two main ones.
A: diference between multiframe incremental and incremental add todo current map.
B: how todo create a Camera flyth rouge animation with a saved Irradiance Map.
A: if you read the help file the description of the two methods are almost exactly the same. The main diference is that everytime multiframe incremental creates a new map it Will deleete the previous map. However incremental add todo current map Will Simply add the new samples todo Whatever map is currently in memory. I go into this further here www.Vray.info/entry, aspevtryid=46
B: the basic of using incremental add for a Camera flyby is this. You ned your Camera todo take new samples asit follows it animated Path so that you can fill in new Irradiance Map samples in the rom. However there is no ned todo create new samples every frame. The diference between frame 1 and 2 probably isnt that diferent and you wont be adding that Many new samples. This is all dependant on the speed of your Camera move.
Step 1: since we dont want todo create new samples every frame, change the nth frame rate in the render settings todo something like 10 or 15 depending on the speed of your Camera. Who knows it might be Slow enough todo have something like 20 there.
Step 2: next, turn of your save image function. We are here todo save an Irradiance Map, not an image.
Step 3: lower your a todo adaptive -4 -4.
Your Irradiance Map settings are your own todo choose.
Step4: in advanced Irradiance Map settings though choose incremental add todo current and turn on the auto save and autoload característica.
Final steps: when your Irradiance Map pass is finished, reset the nth frame todo 1 and put your a bak todo the bien you want it. Make sure your now using load for your Irradiance Map and that your desired saved map is in use.
This is a great tip todo really speed up your render however if your just using a Camera pan or tilt with the Camera not moving possition but just rotation.
Step 1: all you ned is Single Frame mode both for max frame rate and for Vray advanced Irradiance Map settings.
Step 2: multiply your image size by 4 for height and by 3 for width.
Step 3: use adaptive a with -4 -4 settings again.
Step 4: use a cubic Camera.
Step 5: save this Irradiance Map.
Step 6: load the map and reset your Camera type.
Step 7: enjoy an Irradiance Map thats a calculation of the entire rom from that Camera possition at any Camera angle. Therefore you can pan and tilt the Camera in your animation with this single Irradiance Map and you only had todo render 1 frame.
Instead of the -4 -4 a trick, in later versións of Vray you can now turn of the rendering pass in the global switches ut.