JOGL & GLSL shaders | Java Community | Help. Code. Learn. | Page 1

I would like to create a simple shadow shader in glsl, I am using jogl binding. Though when I use the discard function to create transparent, unaltered pixels so I can see the images behind the shader it is not transparent to the background I am displaying.

Here is my java / JOGL code

    public void init(GLAutoDrawable drawable) {
        gl = drawable.getGL().getGL2();
        initShaders(gl);
        gl.glEnable(gl.GL_BLEND);
        gl.glBlendFunc(gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA);
        gl.glEnable(gl.GL_ALPHA_TEST);
        gl.glAlphaFunc(gl.GL_GREATER, 0.1f);
        gl.glMatrixMode(GL_TEXTURE);
        gl.glClearColor(1,1, 1, 1);
        gl.glClear(GL2.GL_COLOR_BUFFER_BIT);
        images();
        game.surface();
        world.setContactListener(new ContactListen());


    }
     public void display(GLAutoDrawable drawable) {
        if (currentTime - lastTime >= 10) {
            lastTime = currentTime;
            angle += step;
        }
        gl = drawable.getGL().getGL2();
        gl.glClearColor(1,1, 1, 1);
        gl.glClear(GL2.GL_COLOR_BUFFER_BIT);

        Display.fill(255, 0, 0, 1);
        Display.fillRect(0, 0, 1920, 1080);

        game.update(System.currentTimeMillis());
        if (renderProgram != 0) {
            gl.glUseProgram(renderProgram);
            gl.glUniform2f(block, 800, 500);
            gl.glUniform2f(mouse, mouseX, mouseY);
        }
    }

GLSL code frag

uniform vec2 light;
uniform vec2 block;

void main(void)
{
vec3 alpha = vec3(0.0, 0.0, 255.0);
float m = ((light.x - gl_FragCoord.x)/(light.y - gl_FragCoord.y));
float  o = ((light.x - block.x)/(light.y - block.y));
gl_FragColor = vec4(alpha, 1.0);
if(gl_FragCoord.x > 500){
discard;
}

}

#JOGL & GLSL shaders