# Start here!

Overview of this lesson.

# Ready to dive into some math?

In this lesson we are going to explore the most fundamental calculation a ray tracer performs:

**ray object intersection.**Since objects in our scenes are modeled using millions of tiny triangles, each intersection is between

**a ray and a triangle.**

In this lesson we'll start with the a simpler version of this problem, the intersection of a ray and a line in 2D:

Finally we'll extend these ideas from two dimensions to work in three dimensions. By the end of this lesson we'll need to solve a pretty meaty system of equations with 4 unknowns:

**a basic understanding of ray tracing**along with a mathematical view of the

**underlying geometry**which makes it all work. How cool is that?

# What do I need to know before starting?

- You should be familiar with the
**slope-intercept form**of a line. Click here to*review a video*or click here to*do an exercise*. - We'll also be using the
**parametric form**which requires you understand**weighted averages of two points**. We covered weighted averages of two points in the Environment Modeling lesson. - Finally we'll need weighted averages of three points which we covered in the Character Modeling lesson.
- You should also have experience solving systems of equations.

Okay, you're ready to go!