Image-based Lighting
Image-based lighting, simply put, is where an image is used to light a scene. In the real world, every object is lit not only by light sources like the sun, lamps etc, but also by everything around. Standing in the middle of a street, a person will be lit by the sun, the blue sky, the brown buildings and the grey floor. Emulating this form of lighting clearly has the potential to create incredibly realistic images.
Images used in this lighting method are a special kind of image called a High Dynamic Range Image or HDRI. This type of image has the capability of lighting a scene with incredible accuracy. In Presenter an HDRI is wrapped around the scene as a sphere, and colour and brightness from the HDRI are cast onto the 3D model to light it.
To give an example of the difference this can make, this is a before shot using normal lights
and this is the same model lit with Image-based Lighting
It is clear the difference this form of lighting can make to rendered images. And the enormous advantage here is that it is much easier to set up than traditional lighting.
On the Lighting Tab, click on the Recommended folder in the left hand side of the palette.
Drag the Environment Light Studio into the palette on the right. This replaces all lights that were in the palette with an Ambient and an Environment light containing our High Dynamic Range Image.
Click on Render to render the scene using the default image contained in this Environment light. This type of render can take slightly longer than traditional lighting methods, but the results are worth the extra time invested.
To use an alternative sample image, click on the Environment folder on the left to show another two example environment lights; a Sky (used in the example above) and a City. Drag the City light over to the right to replace the Environment light in the palette (which should be deleted before rendering).
To manually insert a new HDRI, double click on the Environment icon in the palette, select the Edit... button next to Environment, click on the button next to Filename, and browse to the .hdr file required. For this to work correctly, this HDRI must be a Light Probe HDRI. (Additional Light Probe HDRIs are available from a variety of places on the internet, including Dosch Design.) Click on OK in both dialogs to set the new image to be the light source, and click Render to produce a newly lit rendered scene.