onBeforeCompile = shader => {
                    shader.uniforms.thicknessMap = { value: thicknessMap };
                    shader.uniforms.thicknessDistortion = { value: 0.1 };
                    shader.uniforms.thicknessAmbient = { value: 0 };
                    shader.uniforms.thicknessAttenuation = { value: 0.2 };
                    shader.uniforms.thicknessPower = { value: 2 };
                    shader.uniforms.thicknessScale = { value: 16 };

                    shader.fragmentShader = shader.f