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| -rw-r--r-- | linmath.h | 29 |
1 files changed, 29 insertions, 0 deletions
@@ -582,4 +582,33 @@ LINMATH_H_FUNC void quat_from_mat4x4(quat q, mat4x4 M) q[3] = (M[p[2]][p[1]] - M[p[1]][p[2]])/(2.f*r); } +LINMATH_H_FUNC mat4x4_arcball(mat4x4 R, mat4x4 M, vec2 _a, vec2 _b, float s) +{ + vec2 a; memcpy(a, _a, sizeof(a)); + vec2 b; memcpy(b, _b, sizeof(b)); + + float z_a = 0.; + float z_b = 0.; + + if(vec2_len(a) < 1.) { + z_a = sqrtf(1. - vec2_mul_inner(a, a)); + } else { + vec2_norm(a, a); + } + + if(vec2_len(b) < 1.) { + z_b = sqrtf(1. - vec2_mul_inner(b, b)); + } else { + vec2_norm(b, b); + } + + vec3 a_ = {a[0], a[1], z_a}; + vec3 b_ = {b[0], b[1], z_b}; + + vec3 c_; + vec3_mul_cross(c_, a_, b_); + + float const angle = acos(vec3_mul_inner(a_, b_)) * s; + mat4x4_rotate(R, M, c_[0], c_[1], c_[2], angle); +} #endif |