//     Zcolorシェーダ
//        ver 1.0 2020/08/24
//        by yarunashi@dooon

// xs_begin
// author : 'yarunashi@dooon'
// arg : { id = '0' name = 'type' value = '1' range = '1 2' step = '1'	decimal = '0' }
// arg : { id = '1' name = 'range' value = '8' range = '-255 255' step = '1' decimal = '0' }
// arg : { id = '2' name = 'top' value = '255' range = '0 255' step = '1' decimal = '0' }
// xs_end

float type = i_args[0]; 
float range = i_args[1]; 
float top = min(i_args[2]+1.0, i_volume_size.z); 

float height(vec3 v) {
    float top = -1.0;
    for(float z = i_volume_size.z-1.0; z >= 0.0; z--) {
        if (top < 0.0) {
            if (voxel(vec3(v.x, v.y, z)) > 0.0) {
                top = z;
                if (z == floor(v.z)) return 0.0;
            }
        } else {
            if (z == floor(v.z)) return top - z;
        }
    }
    return -1.0;
}

float map(vec3 v) {  
    if (voxel(v) == 0.0) return 0.0;
    if (floor(v.z) > top) return voxel(v);

    float h;
    if (type == 1.0) {
        h = top - floor(v.z) - 1.0;
    } else {
        h = height(v);
    }
    return i_color_index + sign(range) * floor((h / (top)) * abs(range));
}