1#ifdef GL_ES 2#define LOWP lowp 3precision mediump float; 4#else 5#define LOWP 6#endif 7 8uniform sampler2D u_texture; 9uniform float u_lower; 10uniform float u_upper; 11 12varying LOWP vec4 v_color; 13varying vec2 v_texCoord; 14 15void main() { 16 float distance = texture2D(u_texture, v_texCoord).a; 17 float alpha = smoothstep(u_lower, u_upper, distance); 18 gl_FragColor = vec4(v_color.rgb, alpha); 19}