poker shader

var VSHADER_SOURCE =
    "attribute vec4 a_position; \n" +
    "attribute vec2 a_texCoord; \n" +
    "varying mediump vec2 v_texCoord; \n" +

    "uniform mat4 u_ModelMatrix; \n" + //  变换矩阵
    "uniform float u_Radius; \n" + // 半径
    "uniform float u_ArcLength; \n" + // 弯曲弧长
    "uniform int u_Direction; \n" + // 卷曲方向

    "const float PI = 3.1415926 ;  \n" +
    "const int DIRECTION_LEFT = 1 ;  \n" +
    "const int DIRECTION_RIGHT = 2 ;  \n" +
    "const int DIRECTION_BOTTOM = 3 ;  \n" +

    "vec3 cal_pos(float radius, float length, int direction, vec3 position); \n" +
    "bool predicate(float arc,float len,float x,float y); \n" +
    "float cal_distance(float arc,float len,float x,float y); \n" +

    "void main() \n" +
    "{ \n" +
    "    vec3 result_vec3 = vec3(a_position.x, a_position.y, a_position.z) ;  \n" +
    // 判定需要弯曲的牌面坐标
    "    result_vec3 = cal_pos(u_Radius, u_ArcLength, u_Direction, result_vec3);\n" +
    "    vec4 a_temp = vec4(result_vec3.x, result_vec3.y, result_vec3.z , a_position.w);  \n" +
    "    gl_Position = (CC_PMatrix * CC_MVMatrix * u_ModelMatrix) * a_temp;  \n" +
    "    v_texCoord = a_texCoord;               \n" +
    "} \n" +

    "vec3 cal_pos(float radius, float length, int direction, vec3 position) {\n" +
    "    float _pos =  direction == DIRECTION_BOTTOM ? position.y : position.x ;\n" +
    "    if(_pos >= length && direction != DIRECTION_RIGHT)  {\n" +
    "       return position;\n" +
    "    }else if(direction == DIRECTION_RIGHT && _pos <= length) {\n" +
    "       return position;\n" +
    "    } \n" +
    "    if (direction == DIRECTION_RIGHT) {\n" +
    "        _pos = -_pos; \n" +
    "    }\n" +
    "    float sign = pow(_pos, -1.0) * abs(_pos) == -1.0 ? -1.0 : 1.0; \n" +
    "    float _arc = (sign * length - _pos) / radius;\n" +
    "    float posZ = radius * sin(_arc / 2.0);\n" +
    "    _pos = length - sign * radius * sin(_arc);\n" +
    "    if (_arc > PI) {\n" +
    "        posZ = radius;\n" +
    "        _pos = length + sign * (_arc - PI) * radius;\n" +
    "    }\n" +
    "    if (direction == DIRECTION_BOTTOM) {\n" +
    "       position.y = _pos ;\n" +
    "    }else {\n" +
    "       position.x = _pos ;\n" +
    "    }\n" +
    "    return vec3(position.x, position.y, posZ);\n" +
    "} \n" +
    ' bool predicate(float arc,float len,float x,float y) { \n' +
    '   if(arc == 0.0) return y < len; \n' +
    '   float _arc = PI / 2.0 - arc; \n' +
    '   float _x = len / cos(_arc); \n' +
    '   if (x * tan(_arc) + _x <= y) return false; \n' +
    '   return true; \n' +
    ' } \n' +

    ' float cal_distance(float arc,float len,float x,float y) { \n' +
    '   float _arc = PI / 2.0 - arc; \n' +
    '   float _x = len / cos(_arc); \n' +
    '   return abs(tan(_arc) * x - y + _x) / sqrt( pow(tan(_arc), 2.0) + 1.0); \n' +
    ' } ';
// Fragment shader program
var FSHADER_SOURCE =
    "precision lowp float;   \n" +
    "varying vec2 v_texCoord;  \n" +
    "uniform sampler2D u_Sampler; \n" +
    "void main() \n" +
    "{  \n" +
    "    vec4 color1 =  texture2D(u_Sampler, v_texCoord);   \n" +
    "    gl_FragColor = color1;   \n" +
    "}";