Validate Book 3 progression for milestone v4.0.0

[hollasch]

Run through the book progression before v4 release.

Validate/update rendered images. Make sure that they are PNG format, and sized according to the rendered size specified in the code.

• [ ] 3.1: Cornell box, no stratification
• [ ] 3.2: Cornell box, with stratification (see note below)
• [ ] 3.3: Cornell box, refactored
• [ ] 3.4: Cornell box, with imperfect PDF
• [ ] 3.5: Cornell box, with uniform hemispherical sampling (new render)
• [ ] 3.6: Cornell box, with orthonormal basis scatter function
• [ ] 3.7: Cornell box, sampling only the light, 10 samples per pixel
• [ ] 3.8: Cornell box, light emitted only in the downward direction
• [ ] 3.9: Cornell box with a cosine density PDF
• [ ] 3.10: Cornell box, sampling a hittable light, 10 samples per pixel
• [ ] 3.11: Cornell box, mixture density of cosine and light sampling
• [ ] 3.12: Cornell box with arbitrary PDF functions
• [ ] 3.13: Cornell box with glass sphere, using new PDF functions
• [ ] 3.14: Cornell box using a mixture of glass & light PDFs
• [ ] 3.15: Cornell box with anti-acne color function

Compare render 3.01 and 3.02. They should be the same. If they have slightly different noise, then the text needs to be slightly altered:

You should get exactly the same picture.

→

You should get the same picture, hopefully with less noise

[hollasch]

Review #900.