OpenGL ES应用开发实践指南:iOS卷（源码）

// // UtilityVector.c // // #include "UtilityVector.h" ///////////////////////////////////////////////////////////////// // This function returns an initialized vector. UtilityVector3 UtilityVector3MakeWithArray ( const GLfloat v[3] ) { return UtilityVector3Make(v[0], v[1], v[2]); } ///////////////////////////////////////////////////////////////// // This function returns an initialized vector. UtilityVector3 UtilityVector3Make( const GLfloat x, const GLfloat y, const GLfloat z) { UtilityVector3 result; result.x = x; result.y = y; result.z = z; return result; } ///////////////////////////////////////////////////////////////// // This function returns an initialized vector. UtilityVector2 UtilityVector2Make( const GLfloat x, const GLfloat y) { UtilityVector2 result; result.x = x; result.y = y; return result; } ///////////////////////////////////////////////////////////////// // This function returns an initialized vector. extern UtilityVector4 UtilityVector4MakeWithArray ( const GLfloat v[4] ) { return UtilityVector4Make(v[0], v[1], v[2], v[3]); } ///////////////////////////////////////////////////////////////// // This function returns an initialized vector. extern UtilityVector4 UtilityVector4Make ( const GLfloat x, const GLfloat y, const GLfloat z, const GLfloat w ) { UtilityVector4 result; result.x = x; result.y = y; result.z = z; result.w = w; return result; } ///////////////////////////////////////////////////////////////// // This function returns the vector sum of vectorA and vectorB. UtilityVector3 UtilityVector3Add( const UtilityVector3 vectorA, const UtilityVector3 vectorB) { return UtilityVector3Make( vectorA.x + vectorB.x, vectorA.y + vectorB.y, vectorA.z + vectorB.z); } ///////////////////////////////////////////////////////////////// // This function returns the vector from PositionA to PositionB extern UtilityVector3 UtilityVector3FromPositionToPosition( const UtilityPosition positionA, const UtilityPosition positionB) { return UtilityVector3Make(positionB.x - positionA.x, positionB.y - positionA.y, positionB.z - positionA.z); } ///////////////////////////////////////////////////////////////// // This function returnsa - b UtilityVector3 UtilityVector3Subtract( const UtilityVector3 a, const UtilityVector3 b) { UtilityVector3 result; result.x = a.x - b.x; result.y = a.y - b.y; result.z = a.z - b.z; return (result); } ///////////////////////////////////////////////////////////////// // This function returns vectorA multiplied by the scalar // scalefactor; The returned vector has changed magnitude but // the same direction as vectorA. UtilityVector3 UtilityVector3Scale( const UtilityVector3 vectorA, const GLfloat scalefactor) { return UtilityVector3Make( vectorA.x * scalefactor, vectorA.y * scalefactor, vectorA.z * scalefactor); } ///////////////////////////////////////////////////////////////// // This function returns the length squared a.k.a. magnitude of // vectorA squared. extern GLfloat UtilityVector3LengthSquared( const UtilityVector3 vectorA) { float lengthSquared = (vectorA.x * vectorA.x) + (vectorA.y * vectorA.y) + (vectorA.z * vectorA.z); return lengthSquared; } ///////////////////////////////////////////////////////////////// // This function returns the length a.k.a. magnitude of vectorA. GLfloat UtilityVector3Length( const UtilityVector3 vectorA) { float result = 0.0f; float lengthSquared = UtilityVector3LengthSquared(vectorA); if(FLT_EPSILON < lengthSquared) { // avoid square root of zero error if lengthSquared // is too small result = sqrtf(lengthSquared); } return result; } ///////////////////////////////////////////////////////////////// // This function returns a Unit Vector with the same direction as // vectorA. UtilityVector3 UtilityVector3Normalize( UtilityVector3 vectorA) { const GLfloat length = UtilityVector3Length(vectorA); float oneOverLength = 0.0f; if(FLT_EPSILON < length) { // avoid divide by zero if length too small oneOverLength = 1.0f / length; } return UtilityVector3Scale(vectorA, oneOverLength); } ///////////////////////////////////////////////////////////////// // This function returns the Cross Product vectorA x VectorB. UtilityVector3 UtilityVector3CrossProduct( const UtilityVector3 vectorA, const UtilityVector3 vectorB) { UtilityVector3 result; result.x = vectorA.y * vectorB.z - vectorA.z * vectorB.y; result.y = vectorA.z * vectorB.x - vectorA.x * vectorB.z; result.z = vectorA.x * vectorB.y - vectorA.y * vectorB.x; return result; } ///////////////////////////////////////////////////////////////// // This function returns the Dot Product of vectorA and VectorB. GLfloat UtilityVector3DotProduct( const UtilityVector3 vectorA, const UtilityVector3 vectorB) { return (vectorA.x * vectorB.x + vectorA.y * vectorB.y + vectorA.z * vectorB.z); } ///////////////////////////////////////////////////////////////// // This function returns a Unit Vector in the same direction as // the Cross Product of vectorA and VectorB. UtilityVector3 UtilityNormalVector ( const UtilityVector3 vectorA, const UtilityVector3 vectorB) { return UtilityVector3Normalize( UtilityVector3CrossProduct(vectorA, vectorB)); } ///////////////////////////////////////////////////////////////// // This function returns YES if both p1 and p2 are on the same // side of the line defined by a and b. GLboolean UtilityPointsAreOnSameSideOfLine( UtilityVector3 p1, UtilityVector3 p2, UtilityVector3 a, UtilityVector3 b) { UtilityVector3 cp1 = UtilityVector3CrossProduct( UtilityVector3Subtract(b, a), UtilityVector3Subtract(p1, a)); UtilityVector3 cp2 = UtilityVector3CrossProduct( UtilityVector3Subtract(b, a), UtilityVector3Subtract(p2, a)); return (0 <= UtilityVector3DotProduct(cp1, cp2)); } ///////////////////////////////////////////////////////////////// // This function returns YES if p is inside the triangle formed // by a, b, and c. GLboolean UtilityPointIsInTriangle( UtilityVector3 p, UtilityVector3 a, UtilityVector3 b, UtilityVector3 c) { return (UtilityPointsAreOnSameSideOfLine(p, a, b, c) && UtilityPointsAreOnSameSideOfLine(p, b, a, c) && UtilityPointsAreOnSameSideOfLine(p, c, a, b)); } ///////////////////////////////////////////////////////////////// // This function returns vectorA multiplied by the scalar // scalefactor; The returned vector has changed magnitude but // the same direction as vectorA. extern UtilityVector4 UtilityVector4Scale ( const UtilityVector4 vectorA, const GLfloat scalefactor ) { return UtilityVector4Make( vectorA.x * scalefactor, vectorA.y * scalefactor, vectorA.z * scalefactor, vectorA.w * scalefactor); }