When the object is in a given orientation. If we have a particle of a solid object and we want to measure its position Orientation in 3D space can be held in a quaternion (see class sfrotation)įor an example of how this might be used in a scenegraph node, see
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Since rotation is not commutative the result depends on the order that we applyĪbout how to orientate object to point towards a particular point. To contain angles representing rotation about the x,y and z axes. This can be represented by 3 floating point or double floating point numbers The same directions as the absolute x,y and z coordinates, then apply rotations real = cos (θ/2)Īnother way to specify orientation is to start with the object that has notīeen rotated, in other words the objects local x,y and z coordinates are in This differs from axis-angle in that the real value is cos (θ/2)Īnd the imaginary values are the unit vector divided by sin(θ/2). xĪnother related way to specify orientation is quaternionĪlgebra. We normalise the vector to make it unit length. This requires 4 real numbers to specify, to remove the redundant information Longitude with a unit vector, this gives the axis Using this method the orientation might be specified byĪ related way to specify the orientation would be to replace the latitude and There are many other ways to specify orientation, but all of them require 3 Help me? perhaps where (0,1,0) in local coordinates translates to the maximum
I'm not sure what this angle is measured from, where is zero? can anyone You can rotate about the line between yourself and the point you are lookingĪt. You can rotate to see it upside down, or any angle in-between. However there is also anotherĭirection that you can rotate, if you are looking at a particular point in space, To face by giving its latitude and longitude. May be easier for some people than for others), you can then specify a direction One possible way to define this might be as follows, imagine the earth is transparentĪnd you are at the centre of it (imagining that the world revolves around you When dealing with a solid object, it may not be symmetrical, so we may need Orientation as a rotation from its reference orientation. In the same way, provided we have a reference orientation we can always define However both rotation and orientation can be defined I think of orientation as the current angular position of an object and rotationĪs an operation which takes a starting orientation and turns it into a possiblyĭifferent orientation.
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