I made a follow path constrait with a curve, does it already have a linear interpolation so i can edit it on graph editor? i need the linear interpolation.
When you use a follow path constraint the movement and select Animate Path, there are no keyframes, the movement is determined by a couple of parameters:
1-The number of Frames on the path animation and Evaluation Time of the curve the object is parented to. The default is to move the object through the complete length of the path in 100 frames.
2- A Generator Modifier in in the evaluation time that can be displayed the Graph Editor. The movement starting at 0 and increasing linerarly one unit in X (time) and one unit in (Evaluation time value)
So to determine the speed at which the object will travel through the path there are two options:
A.- Change the number of frames on the curves path animation parameter. Less frames will make the object travel faster across the path. More frames will make it go slower.
B.- Altering the slope of the curve on the generator. A steeper line will make the movement faster, a flatter will slow it down.
If you use the Follow Path constraint but do not activate the Animate Path option. You can move your object using the Offset value, note that depending on your path's direction you might need negative values. That will create keyframes for the object's movement.
Then on the Graph Editor you can set the interpolation you want by pressing T (or Key->Interpolation Type) and selecting Linear.