Image based lighting is a method used in 3D photo realistic rendering in which an image is used to light the scene in conjunction with tradional light models. Image based lighting, or IBL, is generally HDR, although LDR can be used, and provides a larger range of light sampling then can be obtained through traditional light models.
LDR, low dynamic range, works similar to HDR, but offers a much smaller range of lighting information.(information courtesy- Daniel Broadway)
Lets understand what is image-based lighting.
Usually image based lighting works well with GI renderers. However we do have simpler and faster options when we are pressed for time. Or should I say cheaper options.
We would also discuss about image based lighting in GI renderes, but for now lets see how it works with the default rendering system.
In Maya you can use the default skydome that comes with the software for good image based lighting, with an HDR image.
Lets see how can we go about using the HDRdome light script that is available for free.
For those who would also want to concentrate on the theory of IBL( image based lighting) I would rather suggest to go through the information at http://www.debevec.org. where Paul Debevec has explained all about HDR and image based lighting application.
For those who have tried using IBL techniques with GI rendering systems like Mental ray, Vray, Brazil etc…., IBL would have been the preferred method of lighting props since it saves the time that one would rather spend on color correction and composition.
For now lets just see how the script works. I would also not get into details about the parameters of the HDR dome since most of them are self-explanatory.
Start 3ds max. Run the script that you downloaded.
Now a very nice thing that I lately learnt using HDRshop is how to convert my low bit images to HDR images in no time!
I selected the LDR image that goes as the background. I had to convert it to HDR. Heres how you would go about doing the same.
Once I had my hdr image, I brought it in my material editor slot.
When you bring the image make sure you keep the same settings.
Make sure you make the following changes
Now comes the interesting part. Lets run our script.
And you would realize you have a new option under create panel known as CS lights.
Jus like this.
Create an hdr domelight and bring in your mesh.
Add a spherical Uvmap to the dome. Now assign the hdr map to the dome
Place a direct target as the source of sun (just incase if you want to define a sun source)
These are my HDR dome parameters. You can change them according to your requirement.
After you tweak the settings, make sure u click on �Update light colors’.
We are all set. Render the image as Targa, so that we have the alpha channel.
Now composite the render with the background in any image editing or compositing software. I used Photoshop.
We could get much richer results using GI; this was just to demonstrate the concept
All are lit by the same method with the default scanline renderer.