Raytracer

I created this raytracer from scratch as a weekend project, because we were doing ray tracing at my university and I wanted to better understand the topic.

The raytracer is written in Java and is able to read an OBJ file format (as defined here) and read a MTL material file (as defined here). It only uses the vertex, vertex normal and face definition, as other data is not needed. When exporting OBJ file the faces must first be triangulated.

Usage

To use, first compile the Raytracer.java file, then run it.

javac Raytracer.java
java Raytracer

Examples

Examples can be found in the renders folder.

Tasks

• Write custom Vector3 class that is used to represent vectors and is able to do necessary vector operations for ray tracing.
• Write an OBJ and MTL file parsers, so we can import 3D models exported from other 3D software.
• Use the ray tracing algorithm to cast rays through each pixel of our camera plane and check where they intersect with our spheres on scene. I did this first as collision detection with ray is simpler.
• Use the ray tracing algorithm to cast rays through each pixel of our camera plane and check where they intersect with our triangles. The intersection in calculated using the Möller–Trumbore intersection algorithm.
• Implemented shadow ray casting, but instead of tracing only one ray, I send out multiple to get more photorealistic shadows.
• Implemented reflection ray casting, as I also wanted to render reflective planes in my scene.

Optimizations

The raytracer is pretty slow, because when detecting collisions with ray, I am checking all possible triangles in the scene and then finding the closest one. The execution could be made faster if I used bounding volume hierarchy tree and skipped all primitives (triangles) whose axis aligned bounding boxes do not intersect with our ray.

To get more realistic results when calculating reflections, I could send multiple rays in the general direction of reflected ray, calculate the reflected colors and average them. I could also implement transparent materials using the Snell's law.

I did, however, implement the shadow rays like that. So after finding intersection of ray and triangle on scene, I send multiple rays in the direction of a light, which is not a point but rather a sphere. The sadows look more realistic this way.