in vec4 a_color;
in vec2 a_texCoord;
in vec3 a_dir;
in float a_fog;
out vec4 f_color;

uniform sampler2D u_texture0;
uniform samplerCube u_cubemap;
uniform vec3 u_fogColor;
uniform float u_fogFactor;
uniform float u_fogCurve;
uniform bool u_alphaClip;

void main() {
    vec3 fogColor = texture(u_cubemap, a_dir).rgb;
    vec4 tex_color = texture(u_texture0, a_texCoord);
    float alpha = a_color.a * tex_color.a;
    // anyway it's any alpha-test alternative required
    if (alpha < (u_alphaClip ? 0.5f : 0.15f))
        discard;
    f_color = mix(a_color * tex_color, vec4(fogColor,1.0), a_fog);
    f_color.a = alpha;
}