blender-camera-filter-glsl-cell-shading

uniform sampler2D bgl_RenderedTexture;
uniform sampler2D bgl_DepthTexture;

void main()
{
    float depth = texture2D( bgl_DepthTexture, gl_TexCoord[0].xy).r;
    float depth2 = texture2D( bgl_DepthTexture, gl_TexCoord[0].xy + vec2(0.0, 0.003)).r;
    float depth3 = texture2D( bgl_DepthTexture, gl_TexCoord[0].xy + vec2(0.003, 0.0)).r;

    float fac = abs(depth-depth2) + abs(depth-depth3);

    float intensity = 300.0;

    vec4 sub = vec4(fac*intensity, fac*intensity, fac*intensity, 0.0);
    gl_FragColor = texture2D( bgl_RenderedTexture, gl_TexCoord[0].xy ) - sub;
}