Creating a Custom Shader for Post-Processing

Unigine engine allows you to create your own post-effects by writing custom shaders. To write post-effect shaders, you should use the same workflow as for deferred and forward rendering passes: create the material, write vertex and fragment shaders.

This tutorial explains how to create a post-effect material, write shaders for it (both vertex and fragment), add a parameter to the material to be able to specify the value from the UnigineEditor.

See Also

As in all other shaders tutorials, you should create the material first. Let's add the material to the existing *.mat library of your project.

To create post-effect material, you should specify the post pass for shaders and textures.

The material will have the following structure:

<?xml version="1.0" encoding="utf-8"?>
<materials version="2.3">
	
	<!-- Other materials defined here -->

	<!-- Custom post material -->
	<material name="custom_post">

		<!-- Post-effect shaders -->
		<shader pass="post"
			defines="BASE_POST"
			vertex="<your project folder>/data/shaders/vertex/post.vert"
			fragment="<your project folder>/data/shaders/fragment/post.frag"/>
		
		<!-- Textures -->
		<texture name="color" pass="post" unit="0" type="procedural"/>
		
		<!-- Parameters -->
		<parameter name="grayscale_power" type="slider" shared="1" min="0.0" max="1.0"
		flags="max_expand">0.5</parameter>
		
	</material>
	
</materials>

The key features of the post material are:

• Added a post pass shaders and textures.
• Added the shared grayscale_power parameter.

Since we write a simple shader example, let's write a simple shader like the vertex shader for the deferred rendering pass.

1. Write the shader code in the plain text editor:
   Source code (UUSL)

   // Include the UUSL header
   #include <core/shaders/common/common.h>
   
   // Input data struct
   STRUCT(VERTEX_IN)
   	INIT_ATTRIBUTE(float4,0,POSITION)	// Vertex position
   	INIT_ATTRIBUTE(float4,1,TEXCOORD0)	// Vertex texcoords
   	INIT_ATTRIBUTE(float4,2,COLOR0)		// Vertex color
   END
   
   // Output data struct
   STRUCT(VERTEX_OUT)
   	INIT_POSITION		// Output projected position
   	INIT_OUT(float2,0)	// Texcoords (x and y only)
   END
   
   MAIN_BEGIN(VERTEX_OUT,VERTEX_IN)
   	
   	// Set output position
   	OUT_POSITION = getPosition(IN_ATTRIBUTE(0));
   	OUT_DATA(0).xy = IN_ATTRIBUTE(1).xy;
   	
   MAIN_END
   
   // end

   Warning

   You should add a new line (press Enter) after closing the instruction (after MAIN_END command).
2. Save the shader file with the post.vert name and extension to the data/shaders/vertex folder.

The code of the vertex shader is so simple since we don't need to work with the geometry.

This sections contains instruction how to create a fragment shader (also known as pixel shader).

To create the fragment shader for post-process pass, perform the following:

1. Open a plain text editor, and write the following:
   Source code (UUSL)

   // Include the UUSL fragment shader header
   #include <core/shaders/common/fragment.h>
   
   // Define the texture of the scene
   INIT_TEXTURE(0,TEX_SCENE)
   
   INIT_TEXTURE(TEX_SCENE)
   
   // Input values
   STRUCT(FRAGMENT_IN)
   	INIT_POSITION		// Projected position
   	INIT_IN(float2,0)	// Texcoords
   END
   
   // Define the grayscale_power parameter
   CBUFFER(parameters)
   	UNIFORM float grayscale_power;
   END
   
   MAIN_BEGIN(FRAGMENT_OUT,FRAGMENT_IN)
   	
   	// Get the UV
   	float2 uv = IN_DATA(0);
   	
   	// Get the scene color
   	float4 scene_color = TEXTURE_BIAS_ZERO(TEX_SCENE,uv);
   	
   	// Calculate the grayscale
   	float3 gray_scene_color = FLOAT3(dot(float3(0.3f, 0.59f, 0.11f), scene_color.rgb));
   	scene_color.rgb = lerp(scene_color.rgb,gray_scene_color,FLOAT3(grayscale_power));
   	
   	OUT_COLOR = scene_color;
   	
   MAIN_END
   
   // end

   Warning

   You should add a new line (press Enter) after closing the instruction (after MAIN_END command).
2. Save the shader file with the post.frag name and extension to the data/shaders/fragment folder.

Well, let's clarify what is under the hood of this fragment shader:

• We get the texture which was specified in the post-effect material.
• By applying a standard grayscale equation, we change the color of the scene.
• By using lerp function (which performs a linear interpolation), we add the custom parameter to adjust the grayscale power.

See Also

Material has been created, shaders have been written, it's time to use it in the project!

1. Open UnigineEditor and launch your project.
2. Create a new material by inheriting recently created in the Materials settings window.
3. Open the Rendering Settings window by choosing Windows -> Rendering Settings on the main tab (or pressing the Alt+R hotkey combination.

   

4. In the Common tab of the Rendering Settings window, specify the name of the child post material in the Post field.

   

   The grayscale post-effect will be applied.

5. Go to the Material settings, open the Parameters tab of the applied post material.

   

   Set up the grayscale post-effect by adjusting the grayscale power parameter.

   

   The final scene.