Use the "Update" function to make a movie

Unity Engine
1

Hi eveyone,

My problem is simple, I need to make a video from a simulation that I run in Unity. I first wanted to use tools like FRAPS, but my framerate is now too slow. So I thought of simply saving my camera output every frame in a file, and then i will be able to create my movie from the pictures. To do so I fixed the framerate : “Time.captureFramerate = 50;” and each frame I save the output in the Update function of the script handling my cameras :

		Camera cam = cameras[currentCamera];
		int width = (int)cam.pixelWidth;
		int height = (int)cam.pixelHeight;
		Texture2D tex = new Texture2D(width, height, TextureFormat.RGB24, false);
		RenderTexture texture = new RenderTexture(width,height,24);
		Rect save = cameras[currentCamera].rect;
		cam.rect = new Rect(0.0f,0.0f,1.0f,1.0f);
		cam.targetTexture = texture;
		cam.Render();
		cam.rect = save;
		RenderTexture.active = texture;
		tex.ReadPixels(new Rect(0, 0, width, height), 0, 0);
		byte[] bytes = tex.EncodeToPNG(); 
		string filename = Application.dataPath + "/images/" + "Img-"+Time.fixedTime+ ".png"; 
		System.IO.File.WriteAllBytes(filename, bytes); 
		cam.targetTexture = null;
		RenderTexture.active = null;
		Object.DestroyImmediate(texture);
		Object.DestroyImmediate(tex);
		cam.rect = save;

The problem is that it only saves a few frames per second instead of the 50 frames. It seems that the Update function is not called everytime. Does anyone knows what is hapenninng ? How could I fix this ?

Thx,
Quentin.

2

I just tested to save my frames using " Application.CaptureScreenshot(Application.dataPath + “/images/” + “Img-”+Time.fixedTime+ “.png”);" instead of my code, but I still have the same issue, only some of the frames are being saved. Any suggestion ?

Thx,
Quentin.

3

This is only a guess as I haven’t tried it.

Application.CaptureScreenshot is probably quite a slow process, so the computer may only be running at only a few frames per second, hence the small number of captured frames.

A possible alternative is to set Time.timeScale to zero. Capture a screenshot, advance time by 1 frame using Time.time, then capture the next screenshot, and keep repeating. You might need to use ParticleSystem.Simulate or ParticleEmitter.Simulate to advance those systems.

4

Ok, thx for the tip but the time spend on CaptureScreeshot should not affect my frame rate since I was setting the Time.captureFramerate value. I finally solved my problem, and I feel a bit stupid now. I was setting the captureFrameRate value in the Awake function of my script instead of the Start function. It’s now working like a charm.

Thx anyway,
Quentin.

5

Why do you feel stupid? I just encountered the same problem, and IMHO that’s a stupid bug in Unity, nothing else: If you set Time.captureFramerate in Awake(), it is ignored, and reset to 0. :frowning:

Also note that this bug was INTRODUCED in Unity 4.x, as I just confirmed - Unity 3.5 works as expected.