Cohen-Sutherland线段裁剪算法

lass wcPt2D{public:GLfloat x,y;wcPt2D(GLfloat _x, GLfloat _y){x = _x;y = _y;}wcPt2D(){x = 0;y = 0;}};extern int round(const float a);extern void lineBresenham(int nStartX, int nStartY, int nEndX, int nEndY);const GLint winLeftBitCode = 0x1;const GLint winRightBitCode = 0x2;const GLint winBottomBitCode = 0x4;const GLint winTopBitCode = 0x8;inline GLint inside(GLint code ) { return GLint(!code); }inline GLint reject(GLint code1, GLint code2) { return GLint(code1 & code2); }inline GLint accept(GLint code1, GLint code2) { return GLint(!(code1 | code2)); }GLubyte encode ( wcPt2D pt, wcPt2D winMin, wcPt2D winMax){GLubyte code =0x00;if(pt.x < winMin.x)code = code | winLeftBitCode;if(pt.x > winMax.x)code = code | winRightBitCode;if(pt.y < winMin.y)code = code | winBottomBitCode;if(pt.y > winMax.y)code = code | winTopBitCode;return (code);}void swapPts(wcPt2D * p1, wcPt2D * p2){wcPt2D tmp;tmp = *p1; *p1 = *p2; *p2 = tmp;}void swapCodes(GLubyte * c1, GLubyte * c2 ){GLubyte tmp;tmp = *c1; *c1 = *c2; *c2 = tmp;}void lineClipCohSuth(wcPt2D winMin, wcPt2D winMax, wcPt2D p1, wcPt2D p2){GLubyte code1, code2;GLint done = false, plotLine = false;GLfloat m;while( !done){code1 = encode(p1, winMin, winMax);code2 = encode(p2, winMin, winMax);if(accept(code1, code2)){done = true;plotLine = true;}else if( reject(code1, code2)){done = true;}else{if( inside(code1)){swapPts(&p1, &p2);swapCodes(&code1, &code2);}if(p2.x != p1.x )m = (p2.y - p1.y) / (p2.x - p1.x);if( code1 & winLeftBitCode){p1.y += (winMin.x - p1.x ) * m;p1.x = winMin.x;}else if( code1 & winRightBitCode){p1.y += (winMax.x - p1.x) * m;p1.x = winMax.x;}else if( code1 & winBottomBitCode){if(p2.x != p1.x)p1.x += (winMin.y - p1.y)/m;p1.y = winMin.y;}else if( code1 & winTopBitCode){if(p2.x != p1.x)p1.x += (winMax.y - p1.y)/m;p1.y = winMax.y;}}}if ( plotLine)lineBresenham( round(p1.x), round(p1.y), round(p2.x), round(p2.y));}