知易源码002+中文详细注释

// // cocos2d (incomplete) GLU implementation // // gluLookAt and gluPerspective from: // http://jet.ro/creations (San Angeles Observation) // // #import <OpenGLES/ES1/gl.h> #import <math.h> #import "OpenGL_Internal.h" #include "glu.h" void gluPerspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar) { GLfloat xmin, xmax, ymin, ymax; ymax = zNear * (GLfloat)tanf(fovy * (float)M_PI / 360); ymin = -ymax; xmin = ymin * aspect; xmax = ymax * aspect; glFrustumf(xmin, xmax, ymin, ymax, zNear, zFar); } void gluLookAt(GLfloat eyex, GLfloat eyey, GLfloat eyez, GLfloat centerx, GLfloat centery, GLfloat centerz, GLfloat upx, GLfloat upy, GLfloat upz) { GLfloat m[16]; GLfloat x[3], y[3], z[3]; GLfloat mag; /* Make rotation matrix */ /* Z vector */ z[0] = eyex - centerx; z[1] = eyey - centery; z[2] = eyez - centerz; mag = (float)sqrtf(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]); if (mag) { z[0] /= mag; z[1] /= mag; z[2] /= mag; } /* Y vector */ y[0] = upx; y[1] = upy; y[2] = upz; /* X vector = Y cross Z */ x[0] = y[1] * z[2] - y[2] * z[1]; x[1] = -y[0] * z[2] + y[2] * z[0]; x[2] = y[0] * z[1] - y[1] * z[0]; /* Recompute Y = Z cross X */ y[0] = z[1] * x[2] - z[2] * x[1]; y[1] = -z[0] * x[2] + z[2] * x[0]; y[2] = z[0] * x[1] - z[1] * x[0]; /* cross product gives area of parallelogram, which is < 1.0 for * non-perpendicular unit-length vectors; so normalize x, y here */ mag = (float)sqrtf(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]); if (mag) { x[0] /= mag; x[1] /= mag; x[2] /= mag; } mag = (float)sqrtf(y[0] * y[0] + y[1] * y[1] + y[2] * y[2]); if (mag) { y[0] /= mag; y[1] /= mag; y[2] /= mag; } #define M(row,col) m[col*4+row] M(0, 0) = x[0]; M(0, 1) = x[1]; M(0, 2) = x[2]; M(0, 3) = 0.0f; M(1, 0) = y[0]; M(1, 1) = y[1]; M(1, 2) = y[2]; M(1, 3) = 0.0f; M(2, 0) = z[0]; M(2, 1) = z[1]; M(2, 2) = z[2]; M(2, 3) = 0.0f; M(3, 0) = 0.0f; M(3, 1) = 0.0f; M(3, 2) = 0.0f; M(3, 3) = 1.0f; #undef M glMultMatrixf(m); /* Translate Eye to Origin */ glTranslatef(-eyex, -eyey, -eyez); }