Hi,

I'm writing a cpu raytracer using my math library based on this tutorial:

http://www.flipcode.com/archives/Raytracing_Topics_Techniques-Part_1_Introduction.shtml

I got through it up to chapter 6, where I noticed that I get subtle artifacts in the rendering (see pic), which gets even more pronounced when I enable fast mode (only diffuse lighting, 3 fps).

Any idea what am I doing wrong?

download here:

https://docs.google.com/file/d/0B33Sh832pOdOaE1LU3ZqMWZBUzQ/edit?usp=sharing

EDIT: to run the exe on linux, set the LD_LIBRARY_PATH to ../external/lib, ../external/lib/tbb

you'll also need to create a symlink from external/lib/libGLEW.so to libGLEW.so.1.6 (for some reason it links to libGLEW.so.1.6 too... even though I have 1.7)

you'll also need to install gsl (GNU scientific lib)

you can also build it using cmake. To disable the tbb (Intel thread building blocks) and gsl dependencies, set in globals.h USE_QRNG to 0, and COUNT_INTERSECTIONS to 1. Make sure you're not linking to it after this. Note that this will disable threading and usage of quasi random numbers.

Best regards,

Yours3lf

"See pic"? See what pic?

hmm I remember uploading it... nevermind now it should be there.

I remember having similar problem, it was gone after I added multisampling;)

well I did think that that is the solution, but in the original sample the artifacts are not there even without multisampling.

btw did you create a similer gamedev thread?

You have a bug. Using multisampling will only mask the problem. I would try to identify a pixel that gets assigned the wrong color and then step through the code, to see where the computations are going wrong. I have implemented a raytracer before and it didn't have this kind of issue.

I tried to, and fortunately the same pixels are wrong each frame, so I could debug it. I got to the conclusion yesterday that the shading is correct, however I think the intersections may be incorrect. (find_nearest() in main.cpp) I'll do further debugging, but I'm still learning the maths behind it...