Game Maker Studio 2 Channel Shift Shader Tutorial

=====================================================

In this tutorial, we'll delve into the world of shaders in GameMaker: Studio 2. Specifically, we'll focus on creating a simple channel shift shader that manipulates color information within an image or texture.

Shaders are small pieces of code that can be applied to various game objects and assets in real-time, allowing for dynamic visual effects without having to extensively modify the underlying engine itself.

For this example, let's assume you're familiar with basic GameMaker: Studio 2 concepts like creating a new project, adding an instance variable (IV) named 'tex' of type 'surface', and understanding how surfaces work in GMS2. If not, please refer to official documentation or online resources for more information.

Step-by- Step Tutorial

--------------

### Setting up the Project

1. Open GameMaker: Studio 2.

2. Create a new project using the 'Platformer' template as an example; it doesn't matter which genre you choose since we're only concerned with shaders in this tutorial.

3. In your project's assets folder, create a new surface named 'normal_map.png'. This will serve as our normal map for demonstration purposes.

### Creating and Applying the Shader

1. Open up GameMaker: Studio 2's built-in IDE (Integrated Development Environment).

2. Within the Project Explorer on the left-hand side of the GMD editor window, double-click on your current project name.

3. In the new instance that appears, right-click anywhere within it then select 'Insert' > 'New...' from the context menu.

4. From the list provided under 'Resource Type', choose 'Shader'.

5. Name this shader something like 'ChannelShiftExample'.

### Writing the Shader Code

```gml

/// Channel Shift Shader Example

// Define a local variable to hold our input surface data

var _inputSurface = null;

function init(){

// In GMS2, shaders run in both directions: from texture to final output (like usual),

// and vice versa. We'll assume we're working with the former here.

}

function onRenderImage(_target0){

local _x1, _y1, _r1, _g1, _b1 = 0;

if (_target0 != null) {

// Get our input surface data

var s = surf_get_target_surface_2d(0);

for (var i=0; i < image_width(s); i++){

for (var j=0; j < image_height(s); j++) {

_r1 = image_get_r32(_target0, i, j);

_g1 = image_get_g32(_target2d, i, j);

_b1 = image_get_b32(_target3d, i, j);

// Perform your channel shift operation here

_r1 += 128;

_g1 -= 64;

_b1 *= -0.5;

image_set_r8(s, floor(_r1), i, j);

image_set_g8(s, floor(_g1), i, j);

image_set_b8(s, floor(_b1), i, j));

}

// Finally, output our modified surface back to the screen

surf_commit();

}

function onRenderImageBackwards(_target0){

// This function is called after all other shaders have finished rendering,

// which means we can now draw onto _target2d and it will be composited over top of everything else.

}

```

### Applying the Shader

1. In your GameMaker: Studio 2 project's 'Objects' folder, double-click on any instance (doesn't matter what type) to open its properties window.

2. Within the 'Properties' tab, scroll down until you see a section labeled 'Appearance'.

3. Clicking on this will reveal additional options for customizing how your object appears in-game.

### Testing Your Shader

1. Save all changes and press Shift+Enter (or F5) to run your game.

2. Observe the result: if everything was implemented correctly, you should see a window with our normal map applied using the channel shift shader we created earlier!

-------

In this tutorial, we've covered the basics of creating custom shaders in GameMaker: Studio 2, focusing specifically on manipulating color information within an image or texture through use of the `image_get` and `image_set` functions. By following these steps closely along with some basic knowledge of GML (Game Maker Language), you should be able to create more complex visual effects using this powerful feature.

Remember that practice makes perfect; experiment with different shader code, input/ output values, and even try combining multiple shaders together for truly mind-bending results!

Game maker studio 2 channel shift shader