The realization principle of ccaffinetransform correlation transformation of Cocos2d-x

Slightly opengl or 3d basic know the translation/rotation/scaling of the Basic Model view transformation of the implementation principle, recently looked at the next cocos2d-x related parts of the implementation, to understand the implementation of those various coordinate transformations basically, cocos2d-x itself is relatively simple engine.

1. Ccaffinetransform

struct ccaffinetransform {    float  A, B, C, D;     float tx, Ty;};

Represents a transformation matrix:

Construct Ccaffinetransform Structure

Ccaffinetransform __ccaffinetransformmake floatfloat float float float  float  ty) {  ccaffinetransform t;   = A; t.b = b; T.C = C; T.D = D; T.tx = TX; T.ty = ty;   return t;}

2. Unit matrix

ccaffinetransform ccaffinetransformmakeidentity () {    return __ccaffinetransformmake (1.0  0.00.01.00.00.0);}

Construct the Ccaffinetransform as a unit matrix:

3. Panning

Ccaffinetransform ccaffinetransformtranslate (constfloatfloat  ty) {      Return __ccaffinetransformmake (T.A, t.b, t.c, T.D, T.tx + t.a * tx + t.c * ty, T.ty + t.b * TX + T.D * ty);}

The result of the Ccaffinetransform matrix and the shift matrix:

4. Rotate

Ccaffinetransform ccaffinetransformrotate (constfloat  anangle) {    float fsin = sin (anangle);     float fcos = cos (anangle);     return __ccaffinetransformmake (    t.a * fcos + t.c * fsin,                                    * fcos + t.d * fsin,                                    
    * fcos-t.a * fsin,                                    * fcos-t.b * fsin,                                    t.tx,                                    t.ty);}

Right times the rotation matrix around the z axis multiplied by the transformation matrix:

5. Zooming

Ccaffinetransform Ccaffinetransformscale (constfloatfloat  sy) {    return __ccaffinetransformmake (T.A * SX, T.B * SX, T.C * sy, T.D * sy, T.TX, t.ty);}

6. Concate

/*concatenate ' T2 ' to ' T1 ' and return the result:t ' = T1 * T2*/ccaffinetransform Ccaffinetransformconcat (Constccaffinetransform& T1,Constccaffinetransform&T2) {    return__ccaffinetransformmake (t1.a * t2.a + t1.b * t2.c, t1.a * t2.b + t1.b * t2.d,//A, bt1.c * t2.a + t1.d * t2.c, t1.c * t2.b + t1.d * t2.d,//c,dT1.TX * t2.a + t1.ty * t2.c + T2.TX,//TXT1.TX * t2.b + t1.ty * t2.d + t2.ty);//Ty}

The result is equivalent to T2. T1

7. Ccpointapplyaffinetransform

Ccpoint __ccpointapplyaffinetransform (constconst ccaffinetransform& t) {  ccpoint p;  = (float) ((double) t.a * point.x + (double) t.c * point.y + t.tx);   = (float) ((double) t.b * point.x + (double) t.d * point.y + t.ty);   return p;}

8. Ccaffinetransforminvert

Ccaffinetransform Ccaffinetransforminvert (const ccaffinetransform& t) {    float 1 /(T.A * t.d-t.b * t.c);     return __ccaffinetransformmake (determinant * t.d,-determinant * t.b,-determinant * t.c, determinant * t.a,< c10/>* (T.C * T.TY-T.D * t.tx), determinant * (T.B * t.tx-t.a * t.ty));}

The inverse matrix of the matrix is computed by Mathematica:

The realization principle of ccaffinetransform correlation transformation of Cocos2d-x