Waiting for save() / saveFrame() to complete

jimthree

Waiting for save() / saveFrame() to complete

in Contributed Library Questions • 2 years ago

Hi Folks.

I don't know if this is a pure processing question, or a contributed library question (I'm using both GLGraphics and ProScene in my sketch). I have a dataset of points being rendered in 3D, which the user can create camera paths through (using proScene). I have implemented the ability to record the path being played by the using toggling the 'r' key, this activates a save frame function which writes the current frame out to the disk.

The problem is that the sketch does not wait for the saveframe function to complete before rendering the next frame, or rather the sketch compensates for the time taken to save the frame and jumps to where it should be. I need every frame to be rendered to disk so that a smooth animation can be built out of the individual frames.

I'm going to now go and look at createGraphics() to see if that has any effect, but I'm not sure that would work with GLGraphics.

Does anyone have any solutions to this?

cheers

Jim

Replies(7)

PhiLho

Re: Waiting for save() / saveFrame() to complete

2 years ago

To my knowledge, save() is synchronous (unless GLGraphics makes its own PGraphics and overrides it), so it should return only after finishing the operation.
Maybe somebody with better knowledge of this library can shed more light.

andres

Re: Waiting for save() / saveFrame() to complete

2 years ago

The GLGraphics renderer just extents PGraphicsOpenGL, which in turn is a subclass of PGraphics3D. So the save(), saveFrame() methods are the same across all these renderers.

From quickly inspecting the implementation of save and saveFrame in PApplet, it turns out that they actually call the same underlying save() method in PImage, which yes is synchronous.

The reason for this issue is difficult to pinpoint from the description alone as there are many components involved. I'd first try to separate things in order to isolate the cause. Maybe by first disabling Proscene and checking if the frame recording still doesn't work as it should.

That " the sketch compensates for the time taken to save the frame and jumps to where it should be", makes me think that Proscene might be the at fault here. I don't know how the interpolation is implemented, but if Proscene is using the millis() method to "clock" the animation, maybe it generates the jump when things get slow down by saving the frames.

jimthree

Re: Waiting for save() / saveFrame() to complete

2 years ago

Sorry it's taken a while to reply! I've just had some time to run some tests and here are a couple sketches that I think illustrate it.

They both have a record frame function, press 'm' to enter movie mode and again to exit.

The first one uses the barest minimum of external libraries. It works as expected. when you press 'm', the camera movement slows as it saves the frames. Change the max_points var so that it renders enough to make the sketch chug a little bit.

The second sketch uses ProScene, and you should create two key frames using ctrl-1 and then play the path back using '1'. Slow the interpolation right down using 'u' so that it takes a while to move between each keypoint. when you press the 'm' key to save frames, the camera seems to compensate by jumping larger distances rather than waiting to render each frame.

Does this illustrate the point?

Jim

Sketch 1 - no libs.

int recording=0;
int rand = 100;
int max_points = 500000;
float move = 0;
float[] coords_x = new float[1];
float[] coords_y = new float[1];
float[] coords_z = new float[1];
void setup() {
size(640, 360, P3D);
load_data();
camera(-200, 50, 50, 0, 0, 0, 0, 0, -1);
}
void draw() {
background(0);
fill(204, 102, 0);
box(20, 30, 50);
stroke(80);
camera(-200+move, 50, 50, 0, 0, 0, 0, 0, -1);
for (int i=0; i<max_points; i++)
{
point(coords_x[i]-(rand/2),coords_y[i]-(rand/2),coords_z[i]);
}
if(recording==1) saveframe();
move++;
}
void keyPressed() {
if (key == 'm'){
if (recording == 1){
println("Recording Ended");
recording=0;
return;
}
if (recording == 0){
println("Recording: test_xxxx.png");
recording=1;
return;
}
}
}
void load_data()
{
//expand arrays to fit.
coords_x = expand (coords_x,max_points);
coords_y = expand (coords_y,max_points);
coords_z = expand (coords_z,max_points);
for (int i=0; i < max_points; i++)
{
coords_x[i] = random(rand);
coords_y[i] = random(rand);
coords_z[i] = random(rand);
}
}
void saveframe(){
saveFrame("test_#####.png");
print(".");
}

Sketch 2 - using ProScene

import remixlab.proscene.*;
Scene scene;
KeyFrameInterpolator kfi;
int recording=0;
int rand = 100;
int max_points = 500000;
float[] coords_x = new float[1];
float[] coords_y = new float[1];
float[] coords_z = new float[1];
void setup() {
size(640, 360, P3D);
scene = new Scene(this);
load_data();
}
void draw() {
background(0);
fill(204, 102, 0);
box(20, 30, 50);
stroke(80);
for (int i=0; i<max_points; i++)
{
point(coords_x[i]-(rand/2),coords_y[i]-(rand/2),coords_z[i]);
}
if(recording==1) saveframe();
}
void keyPressed() {
kfi = scene.camera().keyFrameInterpolator(scene.path('1'));
if (kfi == null)
return;
if( key == 'u' || key == 'v' ) {
if ( key == 'u')
kfi.setInterpolationSpeed(kfi.interpolationSpeed()-0.05f);
if ( key == 'v')
kfi.setInterpolationSpeed(kfi.interpolationSpeed()+0.05f);
println("interpolation speed = " + kfi.interpolationSpeed());
}
if (key == 'm'){
if (recording == 1){
println("Recording Ended");
recording=0;
return;
}
if (recording == 0){
println("Recording: test_xxxx.png");
recording=1;
return;
}
}
}
void load_data()
{
//expand arrays to fit.
coords_x = expand (coords_x,max_points);
coords_y = expand (coords_y,max_points);
coords_z = expand (coords_z,max_points);
for (int i=0; i < max_points; i++)
{
coords_x[i] = random(rand);
coords_y[i] = random(rand);
coords_z[i] = random(rand);
}
}
void saveframe(){
saveFrame("test_#####.png");
print(".");
}

andres

Re: Waiting for save() / saveFrame() to complete

2 years ago

I would say then that is an issue resulting of the way the Proscene library computes the interpolation.

nakednous

Re: Waiting for save() / saveFrame() to complete

2 years ago

That's the intended behavior, Jim.

KeyFrameInterpolation.startInterpolation uses a timer that updates its frame (position and orientation) for repeated fixed-rate execution, using java.util.Timer.scheduleAtFixedRate. Smoothness may be achieved with fixed-delay execution using java.util.Timer.schedule. You'd need to overload startInterpolation() though.

Regards,

Jean Pierre

jimthree

Re: Waiting for save() / saveFrame() to complete

2 years ago

Thanks for the clarification Jean Pierre, At least I now understand the behaviour!

Could I trouble you for an example of overloading the startInterpolation() function? overloading is beyond my practical abilities right now, although I do understand it in principle. Perhaps the ability to toggle between the two interpolation modes (Fixed rate and relative) would be a great inclusion in a future release of the library.

Thanks to both you and Andres for your continued support, and your respective library writing awesomeness!

Jim

andres

Re: Waiting for save() / saveFrame() to complete

2 years ago

I think the basic idea here is that you can create a subclass of KeyFrameInterpolator in your sketch and override the startInterpolation() method in there. Something more or less like this:

import remixlab.proscene.*;
Scene scene;
SmoothInterpolator kfi;
void setup() {
size(640, 360, P3D);
kfi = new SmoothInterpolator(this);
...
kfi.startInterpolation();
}
void draw() {
...
}
class SmoothInterpolator extends KeyFrameInterpolator {
SmoothInterpolator(PApplet parent) {
super(parent);
}
public void startInterpolation(int period) {
// Your own implementation here...
}
}

For more details about class inheritance in Java, there are many online resources you can use.

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