Fisheye Camera for Cycles

For sample images see:
http://www.dalaifelinto.com/?p=399 (equisolid)
http://www.dalaifelinto.com/?p=389 (equidistant)

The 'use_panorama' option is now part of a new Camera type: 'Panorama'.
Created two other panorama cameras:

- Equisolid: most of lens in the market simulate this lens - e.g. Nikon, Canon, ...)
             this works as a real lens up to an extent. The final result takes the
             sensor dimensions into account also.
             .:. to simulate a Nikon DX2S with a 10.5mm lens do:
                 sensor: 23.7 x 15.7
                 fisheye lens: 10.5
                 fisheye fov: 180
                 render dimensions: 4288 x 2848

- Equidistant: this is not a real lens model. Although the old equidistant lens simulate
               this lens. The result is always as a circular fisheye that takes the whole sensor
               (in other words, it doesn't take the sensor into consideration).
               This is perfect for fulldomes ;)

               For the UI we have 10 to 360 as soft values and 10 to 3600 as hard values (because we can).


Reference material:
http://www.hdrlabs.com/tutorials/downloads_files/HDRI%20for%20CGI.pdf
http://www.bobatkins.com/photography/technical/field_of_view.html

Note, this is not a real simulation of the light path through the lens.
The ideal solution would be this:
https://graphics.stanford.edu/wikis/cs348b-11/Assignment3
http://www.graphics.stanford.edu/papers/camera/


Thanks Brecht for the fix, suggestions and code review.
Kudos for the dome community for keeping me stimulated on the topic since 2009 ;)

Patch partly implemented during lab time at VisGraf, IMPA - Rio de Janeiro.

intern/cycles/render/camera.h

@@ -50,6 +50,15 @@ public:
 	CameraType type;
 	float fov;
 
+	/* panorama */
+	PanoramaType panorama_type;
+	float fisheye_fov;
+	float fisheye_lens;
+
+	/* sensor */
+	float sensorwidth;
+	float sensorheight;
+
 	/* clipping */
 	float nearclip;
 	float farclip;