Created
November 16, 2021 13:53
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A research of glMatrix mat4.lookAt and mat4.targetTo implementation
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// lookAt: | |
if(eye == center){ | |
return I; | |
} | |
// F := center - eye だから | |
// -F -> -f の違いがある | |
z = normalize(eye - center); | |
// s = f * UP ここでは符号一致 | |
x = up * z; // cross product | |
if (x.length() == 0){ | |
x = zero(); | |
} | |
else{ | |
x = normalize(x); | |
} | |
// u = s * f ここでも符号一致 | |
y = z * x; // cross product | |
if(y.length() == 0){ | |
y = zero(); | |
} | |
else{ | |
y = normalize(y); | |
} | |
// z と f の符号は反転しているから求める行列は: | |
// x[0] x[1] x[2] -dot(x, eye) | |
// y[0] y[1] y[2] -dot(y, eye) | |
// z[0] z[1] z[2] -dot(z, eye) | |
// 0 0 0 1 | |
// targetTo: | |
z = normalize(eye - target); | |
x = normalize(up * z); // cross product | |
y = normalize(z * x); | |
// result: | |
// x[0] y[0] z[0] eye[0] | |
// x[1] y[1] z[1] eye[1] | |
// x[2] y[2] z[2] eye[2] | |
// 0 0 0 1 |
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