Ray Tracer Checkpoint 5 - Reflection

Before this checkpoint the ray tracer only calculated local illumination on the surface of an object; with the exception of shadows, the illumination of a point on a surface was completely independent of the rest of the scene. The purpose of this checkpoint is to change that a bit.

The Plan

The goal was to make surfaces reflective based on a coefficient of reflection that each surface will have.
The easiest way to do this was to have each surfaces' material (or texture, as of the last checkpoint) store the coefficient of reflection.

The actually reflection is then implemented using recursion. The basic algorithm is as follows:

• Cast out a ray
• Check for surface collision
• If no collision, use background color (black)
• If collision
• Calculate normal illumination color
• Determine reflection ray
• Start over again, but with reflection ray

To prevent this from looping infinitely, we break out of the recursion whenever a surface isn't reflective (coefficient of 0) or after reaching a certain level of recursion depth.

Results

Basic - Reflective surface

 

The actual algorithm is extremely straightforward, simple to implement, and looks awesome. However, I still struggled for way too long with the blue sphere being in the reflection; turns out my sphere-ray collision detection was broken.

Also, it may be difficult to see, but please note that the specular highlight no longer shows up in the shadowed areas. This, of course, is a triumph. I have to make a note here; huge success. It's hard to overstate my satisfaction.

Ray Tracer Checkpoint 4 - Procedural Shading

The fourth checkpoint is all about procedural shading; basically applying a pattern or texture that is generated on the fly (as opposed to loaded in from an external image) and then applied to a surface or object.

The Plan

I decided to treat the procedural pattern generation as the generation of a "texture," and thus created a Texture class. A Texture object is created with a width and height and stores an array of unsigned chars, it's length being width * height * 3 (it stores the RGB values for every "pixel" of the "texture").

When the ray is cast out from the camera and intersects with a surface, we translate that point of intersection into local coordinates (u, v) relative to some origin on the surface. The easiest case for this is a Polygon which is why it was the focus of this checkpoint. Determining relative (u, v) coordinates shouldn't be too difficult for other objects, however, and I plan on doing so in a later release.

The local (u, v) coordinates then can be used to easily determine the corresponding color from the Texture object. The (u, v) coordinates lying outside the dimensions of the array can be easily handled in a manner similar to actual texture mapping; either repeat the image or stretch the nearest legitimate pixel.

The biggest benefit of using this setup, however, is that it can easily be extended to allow for actual textures to be loaded in. All you have to do is convert a texture into an array of RGB values, which the Simple OpenGL Image Library can actually do for us.

Known Problems

• Shadows are finally casting correctly (WOO!), but ambient light does not work as expected. Illuminating scene fully with ambient light should eliminate all shadows; currently does not.
• Objects are still one-sided and I'm still not sure if I like this or not.
• Loading in textures and converting to RGB values is surprisingly slow using SOIL. Need to figure out why or find a better method.
• There's no real concept of "texture mapping" yet, so when textures are loaded in they're stretched almost unrecognizably.
  

Results

Basic - Procedural Shaded Polygon

 

Ray Tracer Checkpoint 4? - Not Good

WHELP, things are spiraling out of control. I'm still stuck somewhere in the last checkpoint; the restructuring of all my code went a lot worse than I had planned and not much of anything seems to be working.

I now realize the important of backups.

Hopefully I'll be done by Friday. That's pretty acceptable, right? Yeah!

Ray Tracer Checkpoint 3 - Basic Shading

I'm restructuring everything I've done because when I implemented Phong shading everything kind of turned into an ugly blob mess. This post will be better when I finish doing that.

EDIT: I have determined this post is wonderful and needs no updating.

Known Problems

• The lighting on the floor (Polygon3D) looks off and I'm not sure if shadows are correctly cast onto it. 
• The entire code structure is a complete mess; needs restructuring.
• Polygons and Spheres are one sided; if a light source is placed inside a Sphere or behind a Polygon its' light still reaches the other objects. I'm not sure if this is desirable or not.

Results

Basic Phong Shading.

Extra. Two light sources.