Secondary camera with lower frame rate, or render every x frames

Questions & Answers
1

I’d like to render a secondary camera with a lower frame rate than the main one. I tried different things but still don’t have a solution.

  • I tried calling Camera.Render manually, but then I don’t know how to disable camera’s automatic
    rendering.
  • I also tried setting Camera.clearFlags to Nothing and cullingMask to zero, and configure it correctly every x frames, but then the main camera clears the secondary camera.

I guess I can render to texture and only show copies of the texture every x frames, but I would like to optimize, so the camera doesn’t render when it isn’t necessary.

Do you have any other advice? Thank you.

4

This script is working great for me, you can keep the Camera enabled in the Editor, the script will disable it on Start();

[RequireComponent(typeof(Camera))]
public class ManualCameraRenderer : MonoBehaviour {
    public int fps = 20;
    float elapsed;
    Camera cam;

	void Start () {
        cam = GetComponent<Camera>();
        cam.enabled = false;
	}
	
	void Update () {
        elapsed += Time.deltaTime;
        if (elapsed > 1 / fps) {
            elapsed = 0;
            cam.Render();
        }
	}
}
2

Just in case someone finds it useful. I added script to the secondary camera that catches the source RenderTexture every x frames and saves it. Then, every frame, the destination texture is writen with the saved one.

void OnRenderImage(RenderTexture source, RenderTexture destination)
{
    if (m_SavedTexture == null)
        m_SavedTexture = Instantiate(source) as RenderTexture;

    if (Time.frameCount % 20 == 0)
        Graphics.Blit(source, m_SavedTexture);

    Graphics.Blit(m_SavedTexture, destination);
}

The only problem is that the camera keeps rendering every frame, but it just paints the frame on the screen every x frames. This drawback might also be interesting, so the camera keeps an stable frame rate and doesn’t generate peaks.

3

The strategy to disable the camera and only enable it when its rendering doesn’t work well (at all) in the editor, but if you feel like re-examining your solution make sure when testing it you build out.