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OpenGL Billboard
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// http://marina.sys.wakayama-u.ac.jp/~tokoi/?date=20110221 | |
inline void billboard() | |
{ | |
GLfloat m[16]; | |
glGetFloatv(GL_MODELVIEW_MATRIX, m); | |
float inv_len; | |
m[8] = -m[12]; | |
m[9] = -m[13]; | |
m[10] = -m[14]; | |
inv_len = 1. / sqrt(m[8] * m[8] + m[9] * m[9] + m[10] * m[10]); | |
m[8] *= inv_len; | |
m[9] *= inv_len; | |
m[10] *= inv_len; | |
m[0] = -m[14]; | |
m[1] = 0.0; | |
m[2] = m[12]; | |
inv_len = 1. / sqrt(m[0] * m[0] + m[1] * m[1] + m[2] * m[2]); | |
m[0] *= inv_len; | |
m[1] *= inv_len; | |
m[2] *= inv_len; | |
m[4] = m[9] * m[2] - m[10] * m[1]; | |
m[5] = m[10] * m[0] - m[8] * m[2]; | |
m[6] = m[8] * m[1] - m[9] * m[0]; | |
glLoadMatrixf(m); | |
} |
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