HDR, the Difference, and the Application possibilities.
Click on the images for more commentary.
HDR stands for High Dynamic Range. An HDR image stores a lot more color information than your average png or jpeg (which we refer to as LDR or Low Dynamic Range). In fact HDR is capable of storing colors both much brighter and much darker than any current monitor is capable of displaying.
In photography, HDR images are captured by taking multiple exposures (or brightnesses). This means areas that would normally be bloomed out white or in black shadows retain both their color and their detail. (The photos on the left are standard LDR images whereas the images on the right were made with HDR processing.)
Since there are currently no consumer grade HDR displays, I collapsed the HDR images into LDR images for the sake of comparison of color information and retained detail. Notice the sky in the sunset photo and the palm tree in the restaurant photo.
Now, Source Filmmaker is capable of outputting actual HDR files (as the engine itself is HDR capable) called PFM (Portable Floatmap) files. These are the same types of files used to create HDR skyboxes in the engine.
If you use HDR capable photo editing software like Photoshop to edit your renders, you can see some of the benefits in retained color information compared to a png like how the lightsaber turns red instead of grey. I use PFM files to add proper bloom to my renders since how SFM does it isn’t that great.
And since SFM uses HDR, things like motion blur are calculated more accurately to real life. So a lightsaber moving really fast, for example, would have an actual light trail if you’re willing to turn up your motion blur samples slightly.
No particles were used in either of these videos.
The lightsaber uses a red texture with a self-illumination tint value of 1000 which makes it bloom out brightly and leaves a much brighter motion blur, effectively giving it a motion trail at stock and slow shutter speeds.
Jeronimos Monastery, Belem da tonybill Tramite Flickr: A view of the beautiful cloisters of the monastery near Lisbon. It was built by Henry the Navigator, and the tomb of Vasco da Gama is in the attached church.
3-exposure hand-held HDR, pre-processed in LR4, combined and tone mapped in Photomatix, detail enhanced in the lower half.
Definitely best on black, press L.