fluid simulation jit.gl.multiple cubes directions X YZ

hi MATTH, have you checked out the gl3 engine yet? this is a perfect project for extreme speed gains by converting to transform-feedback and gpu-instancing.

There is a shader in the package that demonstrates how to calculate a rotation matrix from a direction vector in GLSL,
mat4 calculate_rotation_matrix(vec3 direction) {
vec3 forwards = normalize(direction);
vec3 outwards;
outwards = cross(forwards, vec3(1.0, 0.0, 0.0)) * forwards.x * forwards.x +
cross(forwards, vec3(0.0, 1.0, 0.0)) * forwards.y * forwards.y +
cross(forwards, vec3(0.0, 0.0, 1.0)) * forwards.z * forwards.z;
vec3 up = cross(forwards, outwards);
outwards = cross(forwards, up);
vec4 row3 = vec4(forwards, 0.0);
vec4 row2 = vec4(normalize(outwards), 0.0);
vec4 row1 = vec4(normalize(up), 0.0);
return mat4(row1, row2, row3, vec4(0.0));
}

And the internet has plenty of solutions for converting a rotation matrix to euler angles for use by jit.gl.multiple, like this one:
Vec3f rotationMatrixToEulerAngles(Mat &R) {
float sy = sqrt(R.at(0,0) * R.at(0,0) + R.at(1,0) * R.at(1,0) );
bool singular = sy < 1e-6;
float x, y, z;
if (!singular) {
x = atan2(R.at(2,1) , R.at(2,2));
y = atan2(-R.at(2,0), sy);
z = atan2(R.at(1,0), R.at(0,0));
}
else {
x = atan2(-R.at(1,2), R.at(1,1));
y = atan2(-R.at(2,0), sy);
z = 0;
}
return Vec3f(x, y, z);
}

porting these solutions to a single Gen patcher should definitely be possible. But as mentioned I would do this in gl3 using GLSL shaders.