Saving Depth buffer for VR Game on Unity - DROP IN FPS

Question

I am building a VR game in Unity and I want to save the depth buffer on to the disk, ideally, I want every 10th frame and maintain the game FPS as 90FPS. So for every 90 frames, I want to get 10 frames of depth. I have tried everything like AsyncGPUReadbackRequest, writing raw Texture 2D files, write raw byte files but nothing seems to work. My game FPS drops to 30-40.

I have one main camera, and one which is a duplicate of the main camera, I don't want to render the depth buffer to the user's eye hence I create another camera. I am not sure if this is even required?

Right now, I am doing : camera.depthTextureMode = DepthTextureMode.Depth;

I have a shader and follow this tutorial: https://www.ronja-tutorials.com/2018/07/01/postprocessing-depth.html

Then: Graphics.Blit(source, destination, material);

Any suggestions on how can I remove the second camera and/or increase faster storing of the depth maps on to the disk?

Update: Removed second camera, still low FPS

Removed the second camera and removed the EncodeToPNG() but still, the FPS is dropping.

Answer 1

You don't need a second camera, you can just copy the depth texture of your current camera to a render texture and write that to a file. This example uses a coroutine to spread the operations out over multiple frames for performance;

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using System.IO;
 
 public class StoreDepthTexture : MonoBehaviour
 {
     private Camera m_Camera;
     private bool m_ShouldSaveDepth = false;
     private bool m_SavingDepth = false;
 
     private void OnEnable ()
     {
         //Make sure our camera writes to depth
         m_Camera = GetComponent<Camera> ();
         m_Camera.depthTextureMode |= DepthTextureMode.Depth;
     }
 
     private void Update ()
     {
         //If we aren't already saving a depth texture, save a new one when the space key is pressed
         if (!m_SavingDepth)
             if (Input.GetKeyDown (KeyCode.Space))
                 m_ShouldSaveDepth = true;
     }
 
     //This is called after the attached camera is finished rendering, meaning the depth texture should be available
     private void OnPostRender ()
     {
         if (m_ShouldSaveDepth)
         {
             //Start saving the depth texture
             StartCoroutine (CaptureDepth());
             m_ShouldSaveDepth = false;
         }
     }
 
     private IEnumerator CaptureDepth ()
     {
         m_SavingDepth = true;
 
         //The depth texture is set as a shader global under the variable name '_CameraDepthTexture' - we can just get a reference to that global
         RenderTexture depth = Shader.GetGlobalTexture ("_CameraDepthTexture") as RenderTexture;
         //The depth is technically stored in the depth buffer which we can't access directly, however if we blit that texture into another texture it will copy the depth into the red colour channel
         RenderTexture tmp = RenderTexture.GetTemporary (depth.width, depth.height, 16, RenderTextureFormat.ARGB32);
         Graphics.Blit (depth, tmp);
 
         //Wait until the next frame
         yield return null;
 
         //Store the last active render texture and set our depth copy as active
         RenderTexture lastActive = RenderTexture.active;
         RenderTexture.active = tmp;
 
         //Copy the active render texture into a normal Texture2D
         //Unfortunately readpixels doesn't work with single channel formats, so ARGB32 will have to do
         Texture2D tex = new Texture2D (depth.width, depth.height, TextureFormat.ARGB32, false);
         tex.ReadPixels (new Rect (0, 0, depth.width, depth.height), 0, 0);
         tex.Apply ();
 
         //Restore the active render texture and release our temporary tex
         RenderTexture.active = lastActive;
         RenderTexture.ReleaseTemporary (tmp);
 
         //Wait another frame
         yield return null;
 
         //Encode the texture data into .png formatted bytes
         byte[] data = tex.EncodeToPNG();
         
         //Wait another frame
         yield return null;
 
         //Write the texture to a file
         File.WriteAllBytes (Application.dataPath + "/depthTexture.png", data);
 
         m_SavingDepth = false;
     }
 }

Saving Depth buffer for VR Game on Unity - DROP IN FPS

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