This is the second version of a simple ray tracer written here at RPI. The second version expanded its capabilities with the inclusion of distributed ray tracing. Detailed information on what distributed ray tracing is can be found in the paper by Cook, Porter and Carpenter: "Distributed Ray Tracing", ACM Computer Graphics, Vol.18, Num.3, July 1984. New capabilities include: Gloss (blurred reflection), translucency (blurred refraction), penumbras (area light sources), motion blur, square intersection routine and a field of view options. The eye can be in any position now and can look towards any direction. Antialising can also be done using stochastic sampling. The old version was also supporting reflections, refractions and shadows using spheres. Here is a list of the files, and what does each file contain: bg.c: bgcolor() evaluates the background color for a given ray. initialize.c: initialize() does some useful setup. intersect.c: sphere() Intersection routine with a sphere. quad() Intersection routine with a square. intersect() Main intersection routine (calls sphere() ). main.c: main() Main body of the program. readfile.c: readfile() Reads in the input data. shade.c: shadow() Calculates the existance of a shadow ray. reflect() Find the reflection vector. refract() Find the refraction vector. shade() Calculate Phong's shading function. trace.c: quickcos() Calculate a fast cos between 0 and pi / 2. quickinvcos() Calculate a fast inverse cosine. rnd() Random number generator between 0 and 1. rand1() Random number generator between -1 and 1. grand() Approximate gaussian random number generator. sample_ray() Take a ray somewhere inside a solid angle. trace_a_ray() Trace a single ray. trace() Trace a single ray inside a solid angle. raytrace() Ray trace the whole picture. vector.c: vadd() vector addition. vsub() vector subtraction. vneg() vector negation. svproduct() scalar - vector product. vdot() dot product. vcross() cross product. norm() normalize a vector. ray.h: Include file for every file used in the raytracer. vector.h: Include file for every file using vectors. The ray tracer is written so it can be easily understood (at least that version), and it is fully commented. Nevertheless, probably it won't be understood by a newcomer. The format of the input file is as follows: <fov> <eye> <dir> <up> <time> <background> <iter> <light> <nos> <nosq> x y z r [ambient] [diff] [spec] refl r g b refr r g b width index refl_diffuse refr_diffuse tx ty tz x y z x y z x y z [ambient] [diff] [spec] refl r g b refr r g b width index refl_diffuse refr_diffuse tx ty tz where: fov field of view eye x y z components of the eye position dir x y z components of the eye direction up x y z components of the up vector time start and end time of the picture background a character specifying the background cuing as follows: n: no cuing. Background has a constant intensity of 0.2 x: the intensity of the background depends of the x direction. y: the intensity of the background depends of the y direction. z: the intensity of the background depends of the z direction. iter number of samples per pixel. light x y z components and solid angle of the light source. nos number of spheres nosq number of squares [ambient] r g b components of ambient [diff] r g b components of diffuse [spec] r g b components of specular refl r g b reflection ratio and color of the reflection refr r g b refraction ratio and color of the refraction width specular width exponent index index of refraction refl_diffuse angle of diffusion when reflecting refr_diffuse angle of diffusion when refracting tx ty tz velocities on the specified axes. Hints: Each frame is a snapsot of a given time length. The time limits are specified in the input file. Each object has the capability to move during that time in a strait line. Motion blur is then observed. If you specify only one sample per pixel, then the blur won't be so good since it evaluates the color of the ray with only one try. The more samples the better, altough anything more than 20 or 30 doesn't do any good. 5 is a good approximation. You can produce penumbras by specifying an angle in the light source. That deviates from real life where each life has an area and the further away you are from the light source, the smaller the penumbras. Here, the size of the blurred shadow does not depend on the distance from the light source. The refl_diffuse and refr_diffuse produce non-sharp reflections and refractions. The argument is in degrees. Anything less than 15 or 20 is good, altough the closer to zero the better you can see it. Known bugs: Polygons appear completely shadowd if the order of the vertices is not right. I always forget which is the right order. ---- The square is defined by only 3 of its points. The first and the second vertices specify one of the sides, and the first and third specify the second. If you assume that second and third specify a side, then you probably won't get the right result. The format of the output file is simple. In the beginning there are 2 integers (that can be read with fread() on a SUN) showing xsize and ysize of the picture. After that follow the pixels in scan-line order. Each pixel uses 3 bytes (one for red, green and blue), totalling 16777216 colors. You can change the format of that file to tailor your needs. It can be done easily by changing the funcion raytrace() in file trace.c If you want you can inform me with any bugs that the program might have or any features that you want the upcoming versions to have. Good luck! George Kyriazis kyriazis@turing.cs.rpi.edu kyriazis@yy.cicg.rpi.edu
