uniform sampler2D texture_data;

uniform vec2 texture_scale;
uniform vec2 texture_offset;
uniform float fog_distance;
uniform vec3 fog_color;
uniform float opacity;

in float vertex_depth;

void main()
{
    vec2 tcfull = vec2(vertex_texcoord.x, 1.0 - vertex_texcoord.y);
    vec4 texel = texture(texture_data, tcfull * texture_scale + texture_offset);
    if (fog_distance > 0.0) {
        float t = clamp(vertex_depth / fog_distance, 0.0, 1.0);
        texel.rgb = mix(texel.rgb, fog_color, t);
        if (t == 1.0) texel.a = 1.0;
    }
    texel.a *= opacity;
    if (texel.a == 0.0) discard;
    frag_color = texel;
}