Hi all…I am wondering if there is a way, through drivers or something else, to control the end point of a path so that, as it reveals itself, the end point stays at a certain location, ie 3D cursor? I am animating a travel path and the path "reveal"is rapid then slow, and I would like a more consistent reveal of the path so that it looks smoother…hope someone can help here.
Thanks
Hello there,
Welcome to Blender Artists.
Is it possible for you to upload some screenshots or reference images, that way we can see what you want it to look like.
Hi there, and thanks for your quick reply…
Im making a video of a bike route, and the path end goes faster and slower, so it looks jumpy… (I’ve used Google Earth Studio tool to import a video frame sequence and the path overlays that)…I used a driver in the end map value to control it throughout the animation with the frame variable, but still that doesnt work, as the end goes out of frame, or moves ahead of frame…Id like to keep the end of the path more or less in the centre of the video sequence so that the path reveal looks smoother…hope this makes sense…
Murray
Thank you for the reply, I understand what you want to do. I personally don’t know how to do what you need, but somebody else on Blender Artists probably will be able to.
Would it be possible for you to upload the Blender file?
I’m unable to upload the blender file as I’m a new member and there is a restriction for this
You could try posting a link to the file on Google Drive.
Good idea!..here you go…
You need to share the file, rather than put a link to your personal drive.
Here is a demo:
Sorry about that…newbie when it comes to sharing via drive…
That’s fine, I did have the option to request access, but that way it wouldn’t work for anybody else, and you would also be able to see my name and email.
Something that might work smoother would be to use the curve as a path and move something else along the path.
Rather than using the curve itself as it seems to be basing the speed from your curve points somehow.
The curve could simply be the source of the animation of say, a cylinder deformed by the curve or a cylinder with segments and use a Shape Key:
This technique could be used:
i made 2 copys of your curve. in the graph-editor one curve has linear speed (i think it’s not desired) and the other one is key-reduced (key: density)
i dont know if i really get what you want, but maybe it looks less jumpy.
the google eath movie is not packed in the file, so i dont know how this looks. 
Thanks Richard. This was a thought I had too, to have an object, perhaps even a bike, as that is what this route is (overlaid on a Google Earth image sequence that wasnt bundled in the Blender file) follow the path, but this still leaves the path going faster then slower as it is of course loccked to the animation of the path…
I like this idea that you suggest with the curtain video, but am not sure how to go about rigging that…an object or empty or whatever that can control more precisely the speed of the path reveal is what Im looking for…the only alternative to this is to keyframe the end map frame by frame, laborious in a 9500 frame project!!
I’d be grateful for any advanced tips on this, as, although Im very familiar with Blender, rigging is not something I’ve spent much time on…
Many thanks for your reply
Murray
I will see if I get more time with it and do something with your file.
In the meantime. Look at that video of the curtain.
What I mean about that is that you can use a tube rather than generating the geometry from the curve itself.
If you use a mesh. Set it up like I did with the curtain.
Put your tube and your curve at the same origin and make sure in object mode they are both oriented in the same direction.
For example straight on the x - in object mode!
Make sure there is no angle on the curve or the tube in object mode.
If so straighten out the curve and make all angles with it in edit mode.
Pro tip. Curves can also get shape keys!
Note the Tube should be the same length as your full curve. And it should have segments so it can bend.
Once you have them both oriented with the origin in the same place, now make a shape key on the tube to basically center all the segments at 0.
If you animate the shape key (with a driver on a bone is best) it will now be able to stretch out along its length.
In this case you would start out with the shape key at 1 (fully compressed) that is your start point.
Now the in the driver you can specify the fidelity of the bone move that will animate the shape key.
For example change the default syntax:
The default syntax reads exactly like this:
Var + 0.0
Change it to this:
Var * 2.0
And the 2 is just an example I find myself using anything from 2 to 50 depending on the case.
So
Var * 10.0
Etc.
For minus movement :
Add Dash and one space to the beginning.
“- Space”
So:
“- Var * 10.0”
The rest should explain itself. Object is the rig and then choose the bone you want to use and the direction you want the bone to be moved or rotated to drive the shape key.
Always use Local for best results.
Think there was discussion with the devs to change that to Local by default.
It is almost (I did say almost now!) not ever useful to use World.
So now that you can drive the shape key, add a curve modifier to the tube using your curve.
With the shape key at 0 the tube should follow the path all the way to the end. It’s not moving at all. But if it does not follow the curve exactly then you set up the orientation improperly.
Assuming that is all go, and you have your sensitivity setting in the driver and your bone. Now, all you have to do it key frame the bone and Bob’s your uncle!
An alternate method is to use an Array modifier to make the tube and animate the number of arrays or also add a shape key to make segment be 0 length.
And then animate it the same as I have just described.
Then some hot shot is going to come along and say you could do all this with Geo Nodes!
And they’ll be right!
Thanks Richard…its probably worth noting at this point that the path is automatically generated from a kml, so I didnt create it, it was imported via Google Earth Studio tools…Ive been following this youtube video
So I guess duplicating that path would be my first step? Sorry, I should have explained this intially…
I did mess with drivers on the end map value using the frame variable, but this didnt help as the end of the path would move wildly in and out of the background image (video) as the camera that is set up in google earth studio moves around quite a bit and changes pace (see the above video - this will make sense)…this is essentially my dilemma…trying to smooth the path so it doesnt look as though we are accelerating very fast in one spot, then deccelerating to an almost stop in another…hope this makes sense…I’ve also looked at the graph editor as a way to "smooth"the movement of the end of the path, but this is fiddly and a lot of work…
Thankyou so much for your assistance here…
here is my packaged blender file, so hopefully you can see the underlying image sequence
It’s just a path. You can probably use it.
And the problem is not drivers and animation, it is using the path also as the mesh rendering element, and trying to animate that property on the curve itself.
This is the source of your problem.
Turn that off and use another mesh that follows the path.
The method I described will solve this problem.
Thanks Richard for all your help here…
Ok, so i followed your instructions above, the curve and cylinder are both placed at 3D cursor.
Some issues Im facing…
The curve is imported from Google Earth Studio…it was originally a kml file, with place markers along the curve to indicate elevation (I think these placemarkers correspond to the control points on the curve), so it has varying curves and height changes based on the topography it traverses, so theres problem number one in that I cant really edit the curve (ie: make it straight as you mention above) as it is “set” really…making it straight defeats the purpose here as it is defining a route on the google earth footage that it overlays…
I have experimented with the cylinder (multiple divisions), oriented in same direction as the curve, having a curve modifier applied, but this goes all weird as I cant determine exactly the orientation of the curve, purely visual…
It seems the key, no pun intended, is the shape key, as you say, but unless I get the starting point and orientation correct for both, this wont work I suspect…
I appreciate, as always, any help you may be able to offer here…
Murray
In a case with this much difficulty I would probably use snapping to recreate a new curve that aligns with the imported one so I could set it up in the optimal way using the new curve.
I think I might have found a simpler solution…
As you mentioned in an earlier post Richard, it seems that the jerkiness of the reveal is related to the control points, very randomly spaced, many on corners, very few on long stretches of road, so I converted the curve to a mesh, used loop tools to evenly space the vertices, and then converted it back to a curve, and Voila!..it seems to have fixed the problem, or at least allowed me to have much more control over the reveal…I think I’ll stick with this…
Many thanks for your advice though
Murray