Implement RealisticCamera

[wahn]

I asked on the PBRT mailing list (pbrt@googlegroups.com):

Are there any example .pbrt files for EnvironmentCamera and/or RealisticCamera? I couldn't find any example scenes using them ...

And Haarm-Pieter Duiker replied with:

https://github.com/hpd/PBRTForMaya/tree/master/maya/renderData

Finding the one example for the RealisticCamera:

> rg realistic
pbrt_feature_demo_camera_realistic.pbrt
29:Camera "realistic"

And the resulting image (rendered with the C++ version of PBRT):

Now, lets add the Rust code to render the same image ...

[wahn]

Matt Pharr answered to the mailing list:

In the pbrt-v3 scenes distribution (https://pbrt.org/scenes-v3.html),                                                                       
sanmiguel/f6-17.pbrt and f6-25.pbrt use the realistic camera.  There                                                                        
are a bunch of lens description files in lenses/ in the example scenes                                                                      
distribution as well.                                                                                                                       
                                                                                                                                            
(We should probably have a few more examples that use those!)                                                                               

[wahn]

Before starting to work on RealisticCamera, let's see how a PerspectiveCamera camera looks like (rendered by the Rust version):

diff --git a/maya/renderData/pbrt_feature_demo_camera_realistic.pbrt b/maya/renderData/pbrt_feature_demo_camera_realistic.pbrt
index 8c22db6..b0b8ac1 100644
--- a/maya/renderData/pbrt_feature_demo_camera_realistic.pbrt
+++ b/maya/renderData/pbrt_feature_demo_camera_realistic.pbrt
@@ -26,11 +26,12 @@ Accelerator "bvh"
 # Camera begin
 Scale -1 1 1
 LookAt 0.000000 4.250000 -45.000000 -0.000000 -0.177129 -2.878684 -0.000000 0.994522 0.104528
-Camera "realistic"
-       "float aperturediameter" [1.0]
-       "float focusdistance" [10.0]
-       "bool simpleweighting" ["true"]
-       "string lensfile" ["../assets/pbrt-v3-scenes/lenses/dgauss.50mm.dat"]
+Camera "perspective"
+# Camera "realistic"
+#      "float aperturediameter" [1.0]
+#      "float focusdistance" [10.0]
+#      "bool simpleweighting" ["true"]
+#      "string lensfile" ["../assets/pbrt-v3-scenes/lenses/dgauss.50mm.dat"]
 # Camera end
 
 WorldBegin

[wahn]

BTW the lens data file used in the example (dgauss.50mm.dat) looks like this:

# D-GAUSS F/2 22deg HFOV			
# US patent 2,673,491 Tronnier"			
# Moden Lens Design, p.312"			
# Scaled to 50 mm from 100 mm			
#    radius	 axpos	N	aperture
29.475	3.76	1.67	25.2
84.83	0.12	1	25.2
19.275	4.025	1.67	23
40.77	3.275	1.699	23
12.75	5.705	1	18
0	4.5	0	17.1
-14.495	1.18	1.603	17
40.77	6.065	1.658	20
-20.385	0.19	1	20
437.065	3.22	1.717	20
-39.73	0	1	20

[wahn]

Chapter in the online book:

http://www.pbr-book.org/3ed-2018/Camera_Models/Realistic_Cameras.html

[wahn]

Since commit cbb1d2d the Rust version seems to render fine using the RealisticCamera:

[wahn]

BTW they rings visible in the C++ version are fixed now:

mmp/pbrt-v3#162