New to After Effects so bear with me, and back in the day I used to use Flash actionscript quite a bit so that way of thinking may not be viable in After Effects. But thought I'd ask anyhoo...
The situation I find myself is a layer with a clip (second layer) as a Luma Mask, ideally I'd like to reuse this animated mask (second layer) at set points in the composition without having to create loads of duplicate or split layers.
So the structure would kind of work like:
Playhead on main timeline reaches beginning of section - Script starts mask animation fade-in playing
Playhead on main timeline reaches end of section - Script starts mask animation fade-out playing
When the next section is reached on the main timeline, a script resets the mask animation to the beginning and replays the above loop.
So in a nutshell - Is it possible to independently control a clip playhead (make it jump to frame 30 for example) or does a clip only play in linear fashion (within AE).
Many thanks for your time.
Regards,
Meeesta
Short answer: No.
Long answer: No. After effects is all about producing linear output. At render time the playhead starts at the first frame and proceeds in a linear fashion towards the last frame, no loops, no jumps. You'll have to use precomps and duplicates.
Related
i am not sure of how to put my question properly so here it goes.
I am running an object detection algorithm which runs at 40 frame per seconds (fps) and fitted on a camera which acts as an 'eye' on a robot. Then, I process the information which is received from the algorithm and pass the actions to my robot.
The issue is each time, the algorithm runs, it gives me slightly new reading. I guess its because as it processes data every 40 times per second, it will give new information. But I don't need new information if my robot doesn't move as most of the objects are at the same position at the previous frame.
My question, how can i only enhance my algorithm to only give me information each time if there is a change in object positions? by comparing last frame reading with current frame reading for example
I think you should try to find the motion estimation of the image ,I think MPG-4 video is using an algorithm like that.
http://www.img.lx.it.pt/~fp/cav/Additional_material/MPEG4_video.pdf
But if you don't want something so sophisticated and you just want to be see if the second image is the sane with the first one just substract them and see the differance. You can also use a Gaussian filter to cut the high frequencies and subtract them and also put a threshhold to check if you want do the procesing or not
I have a video which has frames as shown in my previous image in this question.
How do we detect points from a picture with a particular color on those points
I detected these markers and numbered them as shown in the image given below:
My problem is as follows. After I have detected markers in one frame I need to detect them in another frame and find out how much the marker has moved from its previous location. However on using my code again on the second frame I sometimes in some frames get a different numbering among markers and hence I am not able to track markers from one image to another. Also detecting the markers in each image becomes a cumbersome task and takes a lot of time for a video which has around 200 frames.
How can I track these markers over images so as to know how much a particular marker has moved between frames or simply how can I number these markers such that the numbering never changes viz, the marker numbered 60 remains marker number 60 from frame 1 to frame 200.
As a side question is there a way to actually decrease the processing time such that I don't have to detect the face and eyes in each and every frame (Please refer to the image given in the link in my previous question it makes things clearer).
My problem is as follows. After I have detected markers in one frame I
need to detect them in another frame and find out how much the marker
has moved from its previous location. However on using my code again
on the second frame I sometimes in some frames get a different
numbering among markers and hence I am not able to track markers from
one image to another. Also detecting the markers in each image becomes
a cumbersome task and takes a lot of time for a video which has around
200 frames.
How can I track these markers over images so as to know how much a
particular marker has moved between frames or simply how can I number
these markers such that the numbering never changes viz, the marker
numbered 60 remains marker number 60 from frame 1 to frame 200.
Maybe consider using optical flow technique - http://robotics.stanford.edu/~dstavens/cs223b/ ?
Alternatively try to divide your points cloud into smaller parts and than detect contours. You can divide it using lines or by using this simple idea (not tested or analysed):
Find convex hull of all points (http://en.wikipedia.org/wiki/Convex_hull_algorithms) from your point cloud.
Points which are on the border are in one group.
After processing points from group from point 2, delete them.
Go to point 1.
As a side question is there a way to actually decrease the processing time such that I don't have to detect the face and eyes in
each and every frame
There are few easy things you can do to decrease processing time:
Don't load haar cascade during processing each frame - load it only once, before starting getting frames from camera/video file.
if need to find only one face in each frame, use CV_HAAR_FIND_BIGGEST_OBJECT flag - searching will return only one (the biggest) object. It should be much faster, because search will start from the biggest window and additionally when haar detector find one object it will abort searching and return this object.
play with parameters and check different cascades
once you find face in frame number n than in frame number n+1 don't perform search in whole frame - expand rectangle in which you found face in n frame and search only in this expanded rectangle. How much you should expand it? It depends on how fast user can move his head ;) 50% is big tolerance, but also it's slow. The best option is to find this value on your own.
if your image won't change very much you can skip detecting face in most of frames and just assume that it's in the same place as in previous frame - just check whether frame has changed much. The simplest method is Motion detection using OpenCV (as the author mentioned - it's good idea to use binary threshold on the result of subtraction to ignore changes occurring because of noise). I've used this method in my BSc thesis (Eyetracking system) and it worked very well and improved speed of whole system. Note - it's good idea to force normal (using haar cascade) search from time to time (i've decided to do this once per each 3 frames, but you can try with searching less often) - it will allow you to avoid situation in which used has moved outside camera area and the system didn't noticed it.
i am working on face detection - recognition project in opencv c++ , the code works really slow , there is a lag between the real camera feed and the processed feed , i dont want that lag to be visible to the user .
so can i have a function which just reads a frame from camera and displays it . and all the detection/recognition work can be done on other functions running in parallel ?
also i want my result to be visible on the screen ( a box around the face with necessary details) so can i transfer this data across functions . can i create a vector of Rect datatype which contains all these rectangle data , which can be accessed by all the functions to push new faces and to display them?
i am just searching for a solution to this problem , i know little about parallel computing , if there is any other alternative please give details
thanks
Rishi
Yes, you need to run face detection and recognition code in a separate thread. First you need to copy frame to use it on another thread.
Using vector of Rect will be convinient. But you need to lock mutex when you use vector to prevent problems with parallel access to the same data. And you need to lock mutex while copying frame.
I should note that if your face detection and recognition code runs very slowly, it will never give you up-to-date result: rectangles will be displaced.
First of all note one thing - there will be always some lag. Even if you just display image video from the camera (without any processing) it will be a bit delayed.
It's also important to optimize the process of face detection, parallel computing won't fix all you problems. Here i've written a bit about that (but it's mostly about eye detection within face). Anther technique which it's worth trying is checking whether region (part of image) in which you have found face in last frame have changed or not. General idea is quite simple - subtract region of new (actual) frame from the same region of old (previous one) frame. Then on the result image use binary threshold operation (you need to find threshold value on you own by trying different values - i'm not sure, but i think that i've used something about 30 - don't use too small value, because there is always some difference between two frames, because of noise and little changes in lighting etc). Then count all non-zero pixels and divide this number by number off all pixels of this region ( = width * height ) and multiply by 100. This number will be percentage of changed pixels. If this value is small, you don't have analyze current frame, you can just assume that results of analysis from previous frame are still actual and correct. Note that this technique is working fine only if background isn't changing quickly (like for example trees or water).
I have a CListCtrl which has about 100,000+ entries. The user is presented with a search box to search among these entries. On finding a match, I set that as a selection and scroll to it using EnsureVisible.
This scroll happens instantaneously. I wanted to try and code an animation that looks similar to the ones demoed here (especially the 'Go Top - Easing 2' animation).
I'm thinking, for a basic animation,
Get current selection.
Get target selection.
Compute difference.
Get the pixel height of one item.
Mutiply results of step 3 and 4.
Scroll by an increment of 1 (or some other more optimal value) with a delay until increment = result of step 5.
I tried this and I got incredibly confused. Firstly, is my algorithm okay? Secondly, is there another, better way to achieve this (preferably similar to animation 2 in the link above)?
Your algorithm seems ok for a simple linear scroll. However your link points to scrolls using various easing functions.
Easing functions do not scroll by the same amount each time, but increase or decrease is order to look like they're speeding up, or slowing down.
A common way to work out easing values is to use the result of a sine. If you picture a sine wave and imagine that you can only see one pixel of it at a time, as the wave progresses, the pixel will "ease" at the extremes and accelerate through the middle values.
Your Easing 2 animation is just adding a bit of bounce at the start and end, this is easily achievable by using the a bit of the sine wave past the extremes at each end. eg.
_
/ \
/
\_/
If you want some code, I answered a similar question here in C#.
I just want to do a simple animation (for example in C++ using OpenGL) of some moving object - let's say simple horizontal movement of a square from left to right.
In OpenGL, I can use "double-buffering" method and let's say a user (running my application with the animation) have turned "vertical sync" on - so I can call some function every time when a monitor refreshes itself (I can achieve that for example using Qt toolkit and its function "swapBuffers").
So, I think, the "smoothest" animation that I can achieve, is to "move the square by for example 1 pixel (can be other values) every time monitor refreshes", so at each "frame" the square is 1 pixel further - "I HAVE TESTED THIS, AND IT SURELY WORKS SMOOTHLY".
But the problem arises when I want to have "separate" thread for "game logic" (moving the square by 1 pixel to the right) and for "animation" (displaying current position of the square on the screen). Because let's say the game logic thread is a while loop where I move the square by 1 pixel and then "sleep" the thread for some time, for example 10 milliseconds, and my monitor refreshes for example every 16 milliseconds - the movement of the square "won't be 100% smooth" because sometimes the monitor will refresh two times where the square moves by only by 1 pixel and not by 2 pixels (because there two "different" frequencies of monitor and game logic thread) - and the movement will look "little jerky".
So, logically, I could stay with the first super smooth method, but, it cannot be used in for example "multiplayer" (for example "server-client") games - because different computers have different monitor frequencies (so I should use different threads for game logic (on the server) and for animation (on the clients) ).
So my question is:
Is there some method, using different threads for game logic and animation, which do "100% smooth" animation of some moving object and if some exists, please describe it here, or when I just had some "more complex scene to render", I just would not see that "little jerky movement" which I see now, when I move some simple square horizontally, and I deeply concentrate on it :) ?
Well, this is actually typical separate game-loop behavior. You manage all you physics (movement) related actions in one thread, letting the render thread to do its work. This is actually desirable.
Don´t forget this way of implementation of game loop is to have maximum available frame rate while preserving constant physics speed. At higher FPS, you can not see this effect by any chance, if there is not any other code related problem. Some hooking between framerate and physics for example.
If you want to achieve what you describe as perfect smoothness, you could synchronize your physics engine with VSync. Simply do all your physics BEFORE refresh kicks in, than wait for another.
But this all applies to constant speed objects. If you have object with dynamic speed, you can never know when to draw it to be "in sync". Same problem arises then you want multiple object with different constant speeds.
Also, this is NOT what you want in complex scenes. The whole idea of V-sync is to limit screen tearing effect. You should definitely NOT hook your physics or rendering code to display refresh rate. You want you physics code to run independent of users display refresh rate. This could be REAL pain in multiplayer games for example. For start, look at this page: How A Game Loop Works
EDIT:
I say your vision of perfect smoothness is unrealistic. You can mask it using techniques Kevin wrote. But you will always struggle with HW limits as refresh rate, or display pixelation. For example, you have window of 640x480 px. Now, you want your object to move horizontally. You can move your object by vector heading towards bottom right corner, BUT you must increment object coordinates by float number (640/480). But in rendering, you go to integers. So your object moves jagged. No way around this. In small speed, you can notice it. You can blur it, or make it move faster, but never get rid of it...
Allow your object to move by fractions of a pixel. In OpenGL, this can be done for your example of a square by drawing the square onto a texture (i.e. a one-pixel or larger border), rather than letting it be just the polygon edge. If you are rendering 2D sprite graphics, then you get this pretty much automatically (but if you have 1:1 pixel art it will be blurred/sharp/blurred as it crosses pixel boundaries).
Smooth (antialias) the polygon edge (GL_POLYGON_SMOOTH). The problem with this technique is that it does not work with Z-buffer-based rendering since it causes transparency, but if you are doing a 2D scene you can make sure to always draw back-to-front.
Enable multisample/supersample antialiasing, which is more expensive but doesn't have the above problem.
Make your object have a sufficiently animated appearance that the pixel shifts aren't easy to notice because there's much more going on at that edge (i.e. it is itself moving in place at much more than 1 pixel/frame).
Make your game sufficiently complex and engrossing that players are distracted from looking at the pixels. :)