On pre, post, and render image Question

Unity Engine
1

hi, can anyone explain what does OnRenderImage, OnPostRender and OnPreRender.
i have read the documentation but still don’t understand:(

my goal is create image effects, modify pixel colors, lighting effects, radiosity :smile:

bye

2

Unity Documentation is very clear about this

If you still dont understand, please be more specific

3

Hi, for example, on pre render, “is called before a camera starts rendering the scene” , it means that it works like a Start() function? or make an infinite loop with onpre,onrender and onpost (in order) ?

4

The camera renders the scene once every frame.

–Eric

5

Well, cameras re-render every frame, so I would say it is a “per frame” function. For example, if you want to do something after a camera has rendered as well as all the gui element you need to use the “WaitUntilEndOfFrame” co-routine (the docs also mention this). I remember this from doing a project where we had to “scan” a shap and project it onto a flat plane. Here is the part I used to do that. Note the part where I had to render the camera.

    public void takePics()
    {
        GameObject curObject = GameObject.FindGameObjectWithTag("renderer");
        Renderer r = curObject.GetComponentInChildren<Renderer>();
        string[] temp = curObject.transform.parent.name.Split('_');
        int tempNr = int.Parse(temp[1].Trim());
        r.material.mainTexture = shapes[tempNr-1];
        
        int a = 0;
        foreach (GameObject go in GameObject.FindGameObjectsWithTag("picCam"))
        {
            Camera cam = go.GetComponent<Camera>();
            resWidth = (int)cam.pixelWidth;
            resHeight = (int)cam.pixelHeight;
            cam.Render();
            Texture2D screenShot = new Texture2D(resWidth, resHeight, TextureFormat.RGB24, false);
            screenShot.ReadPixels(new Rect(cam.pixelRect), 0, 0);
            screenShot.name = a.ToString();
            screenShot.Apply();
            images[a] = screenShot;
            a++;
        }
        name = 0;
        r.material.mainTexture = green_shape;
    }