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>Blender Documentation Volume I - User Guide: Last modified April 29 2004 S68</TH
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><H1
CLASS="section"
><A
NAME="section_animation_path"
></A
>Path Animation</H1
><P
>&#13;		A different way to have Objects move in the space is to 
		constrain them to follow a given path.
	</P
><P
>&#13;		When objects need to follow a path, or it is too hard to animate a
		special kind of movement with the keyframe method (Think of a planet
		following its way around the Sun. Animating that with keyframes is
		virtually impossible)	curve objects can be used for the 3D display of an animation
		path. 
	</P
><P
>&#13;		If the Curve object contains more than a single continuous curve
		only the first curve in the object is then used.  
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.ANI.F.S68.401"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartA/rigid_animation/gfx/PathButtons.png"></P
></DIV
><P
><B
>Figure 8. The Action Window with Path Buttons.</B
></P
></DIV
><P
>&#13;		As for tracking, there are two Path animation methods, the old, pre 2.30
		method described here and the new method, which actually defines a constraint,
		which will be described in <A
HREF="x6875.html"
>the Section called <I
>Constraints</I
> in the chapter called <I
>Character Animation</I
></A
>.
		When parenting an Object to a Curve you will be asked to choose
		a <TT
CLASS="literal"
>Normal Parent</TT
> or a <TT
CLASS="literal"
>Follow Path</TT
>
		option. THe Former is what you need for conventional Path animation, but
		other actions needs to be taken later. The second option creates a
		"Follow Path" Constraint, and it is all you need to do.
	</P
><P
>&#13;		Any kind of curve can become a path by setting the option <TT
CLASS="literal"
>CurvePath</TT
>
		Toggle Button in the Animation Buttons window (<B
CLASS="keycap"
>F7</B
>) to ON 
		(<A
HREF="x6084.html#BSG.ANI.F.S68.401"
>Figure 8</A
>). 
	</P
><P
>&#13;		When a Curve has childs it can be turned to a Path by selecting
		it, going int the Editing Context (<B
CLASS="keycap"
>F9</B
>) and activating the <TT
CLASS="literal"
>CurvePath</TT
>
		Toggle button in the Curve and Surface Panel.
		Child objects of the Curve will now move along the specified path.
		It is  a
		good idea to set the Curve to 3D via the <TT
CLASS="literal"
>3D</TT
>
		Toggle Button of the Curve Edit Buttons so that the paths
		can be freely modelled.
	</P
><P
>&#13;		Otherwise, in the ADD menu under Curve-&#62;Path, there is a primitive
		with the correct settings already there. This is a 5th order NURBS
		spline, which can be used to create very fluid, continuous movements.
	</P
><P
>&#13;		Normally a Path is 100 frames long and it is followed in 100 frames by children.
		You can make it longer or shorter by varying the <TT
CLASS="literal"
>PathLength:</TT
>
		Num Button.
	</P
><P
>&#13;		The <I
CLASS="emphasis"
>speed</I
> along a path is determined with an appropriate curve in the
		IPO Window. To see it, in the IPO Window Header button you must select the <TT
CLASS="literal"
>Curve</TT
>
		type for the IPO block. A single channel, <TT
CLASS="literal"
>Speed</TT
> is there.
		 The complete path runs in the IPO Window between the
		vertical values 0.0 and 1.0. Drawing a curve between these values
		links the time to the position on the path. Backward and pulsing
		movements are possible with this. For most paths, an IPO Curve
		must run <I
CLASS="emphasis"
>exactly</I
> between the Y-values 0.0 and 1.0. To achieve this,
		use the Number menu (<B
CLASS="keycap"
>NKEY</B
>) in the IPO Window.  If the IPO Curve is
		deleted, the value of <TT
CLASS="literal"
>PathLen</TT
> determines the duration of
		the path. A linear movement is defined in this case.
		The Speed IPO is a finer way of controlling Path length. The path is long 1 for time IPO,
		and if the time IPO goes from 0 to 1 in 200 frames then the path is 200 frames long.
	</P
><P
>&#13;		Using the option <TT
CLASS="literal"
>CurveFollow</TT
>, in the <TT
CLASS="literal"
>Curve and Surface</TT
> 
		Panel, a rotation is also given to
		the Child objects of the path, so that they permanently point in the
		direction of the path. Use the "tracking" buttons in the <TT
CLASS="literal"
>Anim settings</TT
>
		Panel of the Object (<B
CLASS="keycap"
>F7</B
>) context 
		to specify the effect of the rotation (<A
HREF="x6084.html#BSG.ANI.F.S68.402"
>Figure 9</A
>) as you would do
		for Tracking:
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.ANI.F.S68.402"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartA/rigid_animation/gfx/TrackButtons.png"></P
></DIV
><P
><B
>Figure 9. Tracking Buttons </B
></P
></DIV
><P
>&#13;		<TT
CLASS="literal"
>TrackX, Y, Z, -X, -Y, -Z</TT
> This specifies the
		direction axis, i.e. the axis that is placed on the path.  
	</P
><P
>&#13;		<TT
CLASS="literal"
>UpX, UpY, UpZ</TT
> 
		Specifies which axis must point 'upwards', in the direction of the
		(local) positive Z axis. If the <TT
CLASS="literal"
>Track</TT
> and
            the <TT
CLASS="literal"
>Up</TT
> axis coincides, it is
		deactivated.
	</P
><DIV
CLASS="note"
><P
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><P
>&#13;		Curve paths have the same problem of Bevelled curves for what concern
		the definition of the "Up" direction.
	</P
></TD
></TR
></TABLE
></DIV
><P
>&#13;		To visualize these rotations precisely, we must make it possible for a
		Child to have its own rotations. Erase the Child's rotation with
		<B
CLASS="keycap"
>ALT-R</B
>. Also erase the "Parent Inverse": <B
CLASS="keycap"
>ALT-P</B
>.
		 The best method is to
		'parent' an <I
CLASS="emphasis"
>unrotated</I
> Child to the path with the command
		<B
CLASS="keycap"
>SHIFT-CTRL-PKEY</B
>: "Make parent without inverse". Now the Child jumps
		directly to the path and the Child points in the right direction.
	</P
><P
>&#13;		3D paths also get an extra value for each vertex: the 'tilt'. This can
		be used to specify an axis rotation. Use <B
CLASS="keycap"
>TKEY</B
> in EditMode to change
		the tilt of selected vertices in EditMode, e.g. to have a Child move
		around as if it were on a roller coaster.
	</P
><P
>&#13;		<A
HREF="x6084.html#BSG.ANI.F.S68.404"
>Figure 10</A
> shows a complex application. We
            want to make a fighter dive into a canyon, fly next to the water and then rise 
            again, all this by following it with our camera and, possibly, having
            reflection in the water!
      </P
><P
>&#13;		To do this we will need three paths.
		Path 1 has a fighter parented to it, the fighter will fly following it.
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.ANI.F.S68.404"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartA/rigid_animation/gfx/Path01.png"></P
></DIV
><P
><B
>Figure 10. Complex path animation</B
></P
></DIV
><P
>&#13;		The fighter has an Empty named 'Track' Parented to it in a strategic position.
		A camera is then parented to another curve, Path 2, and follows it, tracking the 
		'Track' Empty. The Fighter has a constant <TT
CLASS="literal"
>Speed</TT
> 
		IPO, the camera has not. It goes faster,
		then slower, always tracking the Empty, and hence the fighter, 
            so we will have very
		fluid movements of the camera from Fighter side, to Fighter front, other side, back, etc.
		(<A
HREF="x6084.html#BSG.ANI.F.S68.405"
>Figure 11</A
>) 
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.ANI.F.S68.405"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartA/rigid_animation/gfx/Path02.png"></P
></DIV
><P
><B
>Figure 11. Some frames, the camera fluidly tracking the fighter.</B
></P
></DIV
><P
>&#13;		Since we want our fighter to fly over a river, we need to set up an Env Map
		for the water surface to obtain reflections. But the Empty used for the calculations
		must be always in specular position with respect
		to the camera... and the camera is moving along a path!
	</P
><P
>&#13;		Path 3 is hence created by mirroring path 2 with respect to the water plane, by
		duplicating it, and using <B
CLASS="keycap"
>MKEY</B
> in Edit Mode with
		respect to the cursor, once the cursor is on the plane.
	</P
><P
>&#13;		The Empty for the Env Map calculation is then parented to this new path, and the Time IPO of
		Path 2 is copied to Path 3. <A
HREF="x6084.html#BSG.ANI.F.S68.406"
>Figure 12</A
> shows a rendered frame.
		Some particle systems were used for trails.
	</P
><P
>&#13;		The scene presents many subtle tricks, as particles for the jet streams, fog, a sky sphere 
		encircling the scene and so on.
	</P
><DIV
CLASS="figure"
><A
NAME="BSG.ANI.F.S68.406"
></A
><DIV
CLASS="mediaobject"
><P
><IMG
SRC="PartA/rigid_animation/gfx/Path03.png"></P
></DIV
><P
><B
>Figure 12. A frame of the final animation.</B
></P
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