Skynet/GPU610

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Ray Tracer

Team Members

1. Michael Wang, (responsibility tbd)
2. Bruno Pereira, (responsibility tbd)
3. ...

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Progress

Assignment 1

Bruno: For assignment 1 I looked into finding a simple Ray Tracer that could be easily understood by someone with no image processing background and benefit from parallelization.

I found ray tracer that matched the criteria I was looking for at http://scratchapixel.com/assets/Uploads/Lesson001/Source%20Code/raytracer.cpp

Looking into Big O notation I believe this program falls under [f(n) = n ^ 2]

I profiled the ray tracer by modifying trace depths, as seen below:

Depth of 70

Each sample counts as 0.01 seconds.

 %   cumulative   self              self     total
time   seconds   seconds    calls  ms/call  ms/call  name
99.99    517.97   517.97   307200     1.69     1.69  Vec3<float> trace<float>(Vec3<float> const&, Vec3<float> const&, std::vector<Sphere<float>*, std::allocator<Sphere<float>*> > const&, int const&)
 0.01    518.00     0.03                             void render<float>(std::vector<Sphere<float>*, std::allocator<Sphere<float>*> > const&)
 0.00    518.00     0.00        1     0.00     0.00  _GLOBAL__sub_I_main

The program spends nearly 100% of all processing with in its Vec3 trace method, this is a recursive method.

Vec3<T> trace(const Vec3<T> &rayorig, const Vec3<T> &raydir,const std::vector<Sphere<T> *> &spheres, const int &depth)

....... .......

if ((sphere->transparency > 0 || sphere->reflection > 0) && depth < MAX_RAY_DEPTH) {

T facingratio = -raydir.dot(nhit);

// change the mix value to tweak the effect

T fresneleffect = mix<T>(pow(1 - facingratio, 3), 1, 0.1);

Vec3<T> refldir = raydir - nhit * 2 * raydir.dot(nhit);

refldir.normalize();

Vec3<T> reflection = trace(phit + nhit * bias, refldir, spheres, depth + 1);

Vec3<T> refraction = 0;

if (sphere->transparency) {

T ior = 1.1, eta = (inside) ? ior : 1 / ior;

T cosi = -nhit.dot(raydir);

T k = 1 - eta * eta * (1 - cosi * cosi);

Vec3<T> refrdir = raydir * eta + nhit * (eta * cosi - sqrt(k));

refrdir.normalize();

refraction = trace(phit - nhit * bias, refrdir, spheres, depth + 1);

}

surfaceColor = (reflection * fresneleffect + refraction * (1 - fresneleffect) * sphere->transparency) * sphere->surfaceColor;

} ... ...

void render(const std::vector<Sphere<T> *> &spheres)

{ unsigned width = 640, height = 480;

Vec3<T> *image = new Vec3<T>[width * height], *pixel = image;

T invWidth = 1 / T(width), invHeight = 1 / T(height);

T fov = 30, aspectratio = width / T(height);

T angle = tan(M_PI * 0.5 * fov / T(180));

// Trace rays

for (unsigned y = 0; y < height; ++y) {

for (unsigned x = 0; x < width; ++x, ++pixel) {

T xx = (2 * ((x + 0.5) * invWidth) - 1) * angle * aspectratio;

T yy = (1 - 2 * ((y + 0.5) * invHeight)) * angle;

Vec3<T> raydir(xx, yy, -1);

raydir.normalize();

*pixel = trace(Vec3<T>(0), raydir, spheres, 0);

} }