OpenGL 4 Shading Language Cookbook - Third Edition

How to do it...

To discard fragments based on alpha data from a texture, use the following steps:

1. Use the same vertex and fragment shaders from the Applying a 2D texture recipe. However, make the following modifications to the fragment shader.
2. Replace the sampler2D uniform variable with the following:

layout(binding=0) uniform sampler2D BaseTex; 
layout(binding=1) uniform sampler2D AlphaTex;

3. In the blinnPhong function, use BaseTex to look up the value of the ambient and diffuse reflectivity.
4. Replace the contents of the main function with the following code:

void main() {    vec4 alphaMap = texture( AlphaTex, TexCoord );    if(alphaMap.a < 0.15 )        discard;    else {        if( gl_FrontFacing ) {            FragColor = vec4(  blinnPhong(Position,normalize(Normal)), ...