<commit_before># Hello, GLSL!

## Exercise

Each exercise has its own directory preloaded with shaders for you to edit.
Generally, there will be
<a href="/open/00-intro-0" target="_blank">a link like this one</a> that will
open that directory for you.

In this exercise's directory you'll find a file called `hello.glsl` that
exports a function called `brightness`. Currently it returns `-1.0` – simply
change it to `1.0` to pass the exercise.

***

## How Shader School Works

For each lesson there is an **expected** and an **actual** shader. The former is
provided by us, and your goal is to simply modify the **actual** shader so that
it matches the expected one.

### The Diff Tool

You'll notice some buttons and a slider below: these are for modifying how the
two are displayed so that you can easily track down any differences between
them.

By default, "slide" mode will be enabled, which will display your
shader's output on the left and our shader's on the right. "Onion" mode will
allow you to overlay the two – in both cases, you can use the slider to adjust
how much is displayed of either the actual or expected output. There's also
"diff" mode, which will display pixels of different values brighter than the<commit_msg>added note on answers/ directory<commit_after># Hello, GLSL!

## Exercise

Each exercise has its own directory preloaded with shaders for you to edit.
Generally, there will be
<a href="/open/00-intro-0" target="_blank">a link like this one</a> that *will
open that directory for you*. If the link does not work for you, you can find
the files for each exercise in the `answers/` directory.

In this exercise's directory you'll find a file called `hello.glsl` that
exports a function called `brightness`. Currently it returns `-1.0` – simply
change it to `1.0` to pass the exercise.

***

## How Shader School Works

For each lesson there is an **expected** and an **actual** shader. The former is
provided by us, and your goal is to simply modify the **actual** shader so that
it matches the expected one.

### The Diff Tool

You'll notice some buttons and a slider below: these are for modifying how the
two are displayed so that you can easily track down any differences between
them.

By default, "slide" mode will be enabled, which will display your
shader's output on the left and our shader's on the right. "Onion" mode will
allow you to overlay the two – in both cases, you can use the slider to adjust
how much is displayed of either the actual or expected output. There's also
"diff" mode, which will display pixels of different values brighter than the
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