void gluLookAt(GLfloat eyex, GLfloat eyey, GLfloat eyez,
GLfloat centerx, GLfloat centery, GLfloat centerz,
GLfloat upx, GLfloat upy, GLfloat upz)
{
GLfloat m[16];// 旋轉矩陣
GLfloat x[3], y[3], z[3];
GLfloat mag;
//生成旋轉矩陣
// Z矢量
z[0] = eyex – centerx;
z[1] = eyey – centery;
z[2] = eyez – centerz;
mag = sqrt(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
if (mag) {
z[0]/= mag;
z[1]/= mag;
z[2]/= mag;
}
// Y矢量
y[0] = upx;
y[1] = upy;
y[2] = upz;
// X 矢量 = Y 叉積 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];
// 重新計算 Y = Z 叉積 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];
// 叉積給出了平行四邊形的面積,對于非垂直單位長度向量;所以在這裏標準化x,y
mag = sqrt(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]);
if (mag) {
x[0]/= mag;
x[1]/= mag;
x[2]/= mag;
}
mag = sqrt(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) = 0.0;
M(1, 0) = y[0];
M(1, 1) = y[1];
M(1, 2) = y[2];
M(1, 3) = 0.0;
M(2, 0) = z[0];
M(2, 1) = z[1];
M(2, 2) = z[2];
M(2, 3) = 0.0;
M(3, 0) = 0.0;
M(3, 1) = 0.0;
M(3, 2) = 0.0;
M(3, 3) = 1.0;
#undef M
glMultMatrixf(m);
// 視點(相機)位置
glTranslatef(-eyex, -eyey, -eyez);
} |
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