Added improved exposure calculation

- based at 1.0-exp(-color) trick in Yafray. But to guarantee backwards
  compatibility, and some more control, Stefano Selleri hacked a useful
  formula for it.
- We now have 2 values to set:
  - "exp": the exponential correction value (0-1)
  - "range": the light range that maps on color 1.0 (0-5)
- Using exp(x) (is e^x) we can much better prevent overflows from render,
  which are currently hard-clipped in Blender. Setting a small 'exp' value
  wil efficiently smooth out high energy and map that back to a color for
  display.
- total formula:
  newcol= linfac*(1.0-exp(col*logfac))
    col, newcol are colors
  linfac= 1.0 + 1.0/((2.0*wrld.exp +0.5)^10)
  logfac= log( (linfac-1.0)/linfac )/wrld.range
    wrld.exp and wrld.range are the button values
- default setting: exp=0.0 and range=1.0 give results extremely close to
  previous rendering.
- graph: http://www.selleri.org/Blender/buffer/Image1.png  for 'exp' setting
  ranging from 0-1, and with 'range'=2

Thanks Stefano for the help!

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 8bb3ab9d5ff..9631bcc958a 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -3929,6 +3929,7 @@ static void do_versions(Main *main)
 		Material *ma= main->mat.first;
 		Scene *sce;
 		Lamp *la;
+		World *wrld;
 		
 		while(ma) {
 			if(ma->fresnel_tra_i==0.0) ma->fresnel_tra_i= 1.25;
@@ -3963,6 +3964,14 @@ static void do_versions(Main *main)
 			if(la->area_sizez==0.0) la->area_sizez= 1.0;
 			la= la->id.next;
 		}
+		wrld= main->world.first;
+		while(wrld) {
+			if(wrld->range==0.0) {
+				wrld->range= 1.0/wrld->exposure;
+				wrld->exposure= 0.0;
+			}
+			wrld= wrld->id.next;
+		}
 	}
 	/* don't forget to set version number in blender.c! */
 }