Chances are you have seen the cool effects of ray tracing. You may have even had your computer crash due to overuse of this advanced technique. But what exactly is going on when a ray trace solution is occurring? There is no doubt that ray tracing is a rendering technique used in 3d software that creates photorealistic images. The reason ray tracing creates such realistic images is because it literally calculates every ray of light and follows each and every one of them until they hit the camera. That means for each pixel, there is a calculation going on, tracing, the ray, hence the name, ray trace.

What is a ray?

In 3d terms, a ray is a line that travels through 3 dimensions and collects data to be rendered. As this ray travels though space, it bounces off various objects, collecting more data as it reaches its end goal, the camera. It mimics how real light behaves as it hits our eyes. You can think of our eyes as the camera, and light as the rays. Because the amount of rays in any given scene is quite numerous, the ray tracing calculation is reversed to that of real light. Only light that hits the camera is calculated backwards to the light source.

Three Controls

Ray tracing has three main controls, depth, pixel count, and number of light sources. Essentially, the more you have of these, the longer the render time will be.

Ray tracing depth refers to the amount of times a ray is allowed to come in contact with various objects in the scene. Most programs have slightly different ways of calculating depth. Reflection rays bounce off objects in a manner that will reflect the environment. A shadow ray is calculated once a ray hits a target. A refraction ray is generated anytime an object is defined as transparent.

Since ray tracing works in a backwards manner, the amount of lights will directly effect the amount of times a ray must be trace. Therefore, if you have 10 lights in your scene, the amount of render time is going to much greater than if you had 2 or 3 lights in your scene.

In the same regards, the more objects you have in your scene, the higher the amount of pixels to be rendered will be. Since rays must traced through every pixel, you can see how having more objects would naturally take more time to render.