dipityPix app

Friday, July 15, 2016

I do have a bug

I questioned whether this was right:



I was concerned about the bright bottom and thought maybe there was a light tunnel effect.   I looked through my stuff and found a dented cube, and its bottom seemed to show total internal reflection:
The light tunnel effect might be happening and there is a little glow under the cube, but you cant see it thought the cube.   Elevating it a little does show that:

Digging out some old code and adding a cube yielded:
This is for debugging so the noise was just because I didn't run to convergence.   That does look like total internal reflection on the bottom of the cube, but the back wall is similar to the floor.   Adding a sphere makes it more obvious:
Is this right?   Probably.



Wednesday, July 13, 2016

Always a hard question: do I have a bug?

In testing some new code involving box-intersection I prepared a Cornell Box with a glass block, and first question is "is this right?".    As usual, I am not sure.    Here's the picture (done with a bajillion samples so I wont get fooled by outliers):


It's smooth anyway.   The glass is plausible to my eye.   The strangest thing is how bright the bottom of the glass block is.   Is it right?    At first I figured bug.   But maybe that prism operates as a light tunnel (like fiber optics) so the bottom is the same color as a diffuse square on the prism top would be.   So now I will test that hypothesis somehow (google image search?   find a glass block?) and if that phenomenon is right and of about the right magnitude, I'll declare victory.