bloomfilter.frag

Create bloomfilter.frag under the shaders directory.

Input variables

We only need the texture coordinate and the texture itself.

in vec2 texCoord;

// render-to-texture of the scene generated in the 1st pass
layout (binding=1) uniform sampler2D renderTex;

Scene rendering as a texture

From this shader, we start to use the 430 texture binding:

// render-to-texture of the scene generated in the 1st pass
layout (binding=1) uniform sampler2D renderTex;

With this binding setting, you no longer need to set the texture unit with glUniform().

Output variables

The only output variable we need is the ouput fragment colour.

out vec4 colour_out;

main()

Read the pixel colour of the scene

First, read the pixel colour from the scene texture:

vec4 colour = texture(renderTex, texCoord);

Calculate the brightness

We are calculating the brightness of a pixel based on the following RGB coefficients:

float brightness = dot(colour.rgb, vec3(0.2126, 0.7152, 0.0722));

Filtering

In this fragment shader, we simply use a brightness threshold.

The following is an example using a thresholdof 0.9

    // filter the bright part based on a threshold
    if(brightness > 0.9)
        colour_out = vec4(colour.rgb, 1.0);
    else
        colour_out = vec4(0.0, 0.0, 0.0, 1.0);

Full Source Code

// bloomfilter.frag
#version 430

in vec2 texCoord;

// render-to-texture of the scene generated in the 1st pass
layout (binding=1) uniform sampler2D renderTex;

out vec4 colour_out;

void main()
{
    vec4 colour = texture(renderTex, texCoord);

    // check whether fragment output is higher than threshold, if so output as brightness color
    float brightness = dot(colour.rgb, vec3(0.2126, 0.7152, 0.0722));
    
    // filter the bright part based on a threshold
    if(brightness > 0.9)
        colour_out = vec4(colour.rgb, 1.0);
    else
        colour_out = vec4(0.0, 0.0, 0.0, 1.0);
}