Eduardo J. González
CAP 6938 Projects
Advanced Graphics - Ray Tracing

 Spring 2003 Dr. Reinhard

	Ray Tracer 1.0 (diffuse)	Due: 1/23/03
	This simple ray tracer provides the basic functionality of what makes a ray tracer. We start with a background picture (the sky) and some basic geometry (3 spheres). After setting up a virtual camera, we compute a ray for every pixel in our destination buffer (final image). Each ray must be checked for intersection against all geometry in the scene. The nearest point of intersection determines the final color of the pixel. In this simple example, diffuse lighting is computed, where the camera itself is the light source.

	Ray Tracer 1.1 (shadows)	Due: 1/30/03
	Several improvements since that last version: diffuse materials, lighting and shadowing computation for an arbitrary number of light sources. The image to the left was created with Varol’s scene description (Thanx). In the image, the only primitives used are spheres and triangles. I added another primitive (not shown): an axis-aligned box. The bounding volume hierarchy is still a work-in-progress, which I expect to have up and running by Friday (a bit late… sorry).
	--Update— (bounding volume hierarchy) (3D File Format Converter)
	Ok… the bounding volume hierarchy works fine now. The horse to your left has 39,700 triangles, 2 point lights, a resolution of 800 x 800, and I was able to render it in less than 10 seconds. Another scene (not shown) has 58,700 triangles, 2 lights, and the same resolution… I was able to render that in 12.6 sec. Because the scene file(s) are so big, I will not post them online, but if you want it (them), just ask for them, and I’ll email them back to you. Email: geduardo@cs.ucf.edu

	Ray Tracer 1.2 (metals/mirrors)	Due: 2/6/03
	The image to the left demonstrates the new feature of the ray tracer… reflections! A blue metallic cube is surrounded by three spheres of different colors. The surface of the box should act as a mirror, and that seems to be working. The program still needs to calculate dielectric properties before it fully meets this week’s requirements. It seems that (just like last week) I’ll be a day or two off schedule.
	--Update— (dielectrics)
	Now the dielectric stuff is working. On the left is a modified scene from Varol’s. It demonstrates both mirrors and reflectance from a dielectric (the sphere). The way I coded the dielectric behavior of spheres, it does not check for objects INSIDE the object. I had to move the glass sphere away from the green one in order for this scene to look correct.
	This is just another sample of metals and dielectrics. I can claim that this scene is my own. :o) I made the floor out of “boards” of different colors. The purpose for this is to show the bending of light through the dielectric sphere. There is also a reflective (metal) triangle that shows the sphere from a different angle.

	Ray Tracer 1.3 (specular reflections)	Due: ?????
	This update includes the use of specular reflection. The technique I decided to implement is known as Phong Shading. Specular highlights (shiny surfaces) are computed using the reflected ray as it comes from the light sources. Another techniques involves the use of the half-angle ray “thing”, which gives similar results.

	Ray Tracer 1.4 (Jittering)	Due: ?????
	This update includes the option to eliminate some “jaggies” by using an anti-aliasing technique known as jittering. In this technique, every outgoing ray (from the camera) is somewhat distorted in direction by a random value. This will cause edges to become a little more “fuzzy.” The animation to the left should help you see the benefits of jittering. Hopefully you’ll notice the difference although the image is kind of small. Other anti-aliasing techniques (not yet implemented) are super sampling, and filtering (more evident when using textures).

	Ray Tracer 1.5 (textures)	Due: ?????
	The new feature to our ray tracer is the ability to texture diffuse/specular surfaces. I did not implement textures to materials of type metal or dielectric. It just doesn’t make any sense to me to texture mirror-like surfaces or see-through ones. A given 2D image is mapped on the 3D geometry by determining the offset onto the image from the point of intersection. For triangles, this is given by using barycentric coordinates. For spheres, we use polar coordinates to determine the offset onto the function. The scene to your left contains 4 point-light sources, and 2 textured spheres. They are textured with a water texture I found.

	Ray Tracer 1.6 (Fog)	Due: ?????
	This feature was not part of the specifications for the class. I’m just hoping tricks like these can get me a few extra points. J Anyways… this new feature supports fog rendering. It simply determines how far away from the camera the ray-intersection occurred, and the further away, the more “fog color” is blended to the output color. This can be interpolated in several ways… I did it the easy way, so it’s interpolated linearly, but there is room for improvement. I believe this is such a cool effect, that it deserves an extra 2.5 points. j/k

	Ray Tracer 1.7 (Grids)/(Uniform Spatial Subdivisions)	Due: ?????
	This is a speed optimization similar to the bounding volume hierarchy (BVH). The data structure divides the space in a 3D grid of boxes, where each box holds information about overlapping geometry. Ray/scene intersections are sped up by avoiding unnecessary tests with geometry that do not come close to crossing the ray’s path. For some reason, my BVH generally performs better than my grid structure. L At any rate, this new feature allowed me to render the image on the left (59,000 triangles, 2 point lights) in about 20 secs.

	Ray Tracer 1.8 (aerial light sources)	Due: ?????
	The next feature to the ray tracer is spherical (aerial) light sources. A light is no longer defined by an infinitely small point in space. In order to render soft shadows (as a result from an aerial light source), we must sample the light source throughout its surface several times before computing the final color. The image to the right sampled the spherical light 75 times per shadow-test. I coded the equations exactly as they are in the book. Equation 15.4 from pg. 120, and those from pages 123 and 124. Since I have yet to program tone-mapping, I had to hard code some “damping” operator to keep my colors somewhat under control.

	Ray Tracer 1.9 (tone mapping)	Due: ?????
	Our next improvement consists of the support for tone mapping. For testing purposes, I use a scene made up of 3 lights, where all lights are RGB(1,1,1). Without tone mapping, our final image would look either flat shaded (if colors are cropped), or completely messed up if nothing is done to correct it (shown left). I implemented the basic tone mapping operator and the slightly less complicated operator. I played around with the alpha value, to obtain the results shown to the left (click to enlarge).