Optimizing a raytracer

["Róbert László Páli"]

Hello!

I am writing an unbiased raytrace renderer in D. I have good 
progress, but I want to make it as fast as possible where I can 
do it without compromises.

I use a struct with three doubles for vector and color 
calculations and I have operator overloading for them. Many 
vectors and colors are created during the tracing calculations.

I thought, using classes may require too much memory, because 
they are not destructed on scope end, and maybe speed reduction 
when GC kicks in.

Is my assumptions that in this case struct are more wise?

To avoid the constructing many vectors and colors, I thought to 
use ref arguments, but I also heard that ref functions are not 
inlined. What would generate the fastest code for a cross-product 
for example?

What compiler and compilations flags should I use to generate the 
fastest code? My main target is sixty-four bit machines, 
cross-platform. What optimizations can I assume for various 
compilers? Are only once used local variables inlined? So it 
secure to extract local variables only to make the code more easy 
to understand?

Thanks is Advance!
Róbert László Páli