VRTK_ScreenFade does not work with scriptable render pipelines

[krzys-h]

Environment

• Source of VRTK: GitHub
• Version of VRTK: 3.3.0 bf584452ff8df5f5fd71ae148b642131b5820fb7
• Version of Unity3D: 2018.3.5f1
• Hardware used: VR Simulator
• SDK used: VR Simulator, but everything except for SteamVR seems to use the same code path

Steps to reproduce

Set up a project using experimental LWRP for VR in Unity. Import VRTK into it. Do the following:

VRTK_HeadsetFade fade = gameObject.AddComponent<VRTK_HeadsetFade>();
fade.Fade(Color.black, 5.0f);

Expected behavior

The screen should fade.

Current behavior

The screen does not fade. OnPostRender in the VRTK_ScreenFade script is not called when scriptable render pipelines are used.

[krzys-h]

Also see https://forum.unity.com/threads/feedback-wanted-scriptable-render-pipelines.470095/page-8#post-3408481 for explanation why OnPostRender was removed

[krzys-h]

I tested on SteamVR now as well - it doesn't work either, the SteamVR_Fade script has exactly the same problem.

Here is the solution I ended up with for now, it took a while to figure out since there aren't many resources about the scriptable pipelines yet but it works:

using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Experimental.Rendering.LightweightPipeline;
using UnityEngine.Rendering;
using VRTK;

public class VRTK_ScreenFade_LWRP : VRTK_ScreenFade, IAfterRender
{
    private FadeRenderPass fadeRenderPass;

    public ScriptableRenderPass GetPassToEnqueue()
    {
        return fadeRenderPass ?? (fadeRenderPass = new FadeRenderPass(this));
    }

    private class FadeRenderPass : ScriptableRenderPass
    {
        private VRTK_ScreenFade_LWRP screenFade;
        private Mesh quad;

        public FadeRenderPass(VRTK_ScreenFade_LWRP screenFade)
        {
            this.screenFade = screenFade;

            quad = new Mesh();

            Vector3[] newVertices = new Vector3[4];
            newVertices[0] = new Vector3(0f, 0f, 0.9999f);
            newVertices[1] = new Vector3(0f, 1f, 0.9999f);
            newVertices[2] = new Vector3(1f, 0f, 0.9999f);
            newVertices[3] = new Vector3(1f, 1f, 0.9999f);
            quad.vertices = newVertices;

            Vector2[] newUVs = new Vector2[newVertices.Length];
            newUVs[0] = new Vector2(0, 0);
            newUVs[1] = new Vector2(0, 1);
            newUVs[2] = new Vector2(1, 0);
            newUVs[3] = new Vector2(1, 1);
            quad.uv = newUVs;

            int[] newTriangles = new int[] { 0, 1, 2, 3, 2, 1 };
            quad.triangles = newTriangles;

            Vector3[] newNormals = new Vector3[newVertices.Length];
            for (int i = 0; i < newNormals.Length; i++)
                newNormals[i] = Vector3.forward;
            quad.normals = newNormals;
        }

        public override void Execute(ScriptableRenderer renderer, ScriptableRenderContext context, ref RenderingData renderingData)
        {
            // interpolation code copy-pasted from current OnPostRender implementation
            if (screenFade.currentColor != screenFade.targetColor)
            {
                if (Mathf.Abs(screenFade.currentColor.a - screenFade.targetColor.a) < Mathf.Abs(screenFade.deltaColor.a) * Time.deltaTime)
                {
                    screenFade.currentColor = screenFade.targetColor;
                    screenFade.deltaColor = new Color(0, 0, 0, 0);
                }
                else
                {
                    screenFade.currentColor += screenFade.deltaColor * Time.deltaTime;
                }
            }
            
            if (screenFade.currentColor.a > 0 && screenFade.fadeMaterial)
            {
                screenFade.currentColor.a = (screenFade.targetColor.a > screenFade.currentColor.a && screenFade.currentColor.a > 0.98f ? 1f : screenFade.currentColor.a);
                
                screenFade.fadeMaterial.color = screenFade.currentColor;
                screenFade.fadeMaterial.SetPass(0);

                CommandBuffer cmd = CommandBufferPool.Get("ScreenFade");
                cmd.SetViewProjectionMatrices(Matrix4x4.identity, Matrix4x4.Ortho(0.0f, 1.0f, 0.0f, 1.0f, -1.0f, 100.0f));
                cmd.DrawMesh(quad, Matrix4x4.identity, screenFade.fadeMaterial);
                context.ExecuteCommandBuffer(cmd);
                CommandBufferPool.Release(cmd);
            }
        }
    }
}

diff --git a/Assets/VRTK/Source/SDK/SteamVR/SDK_SteamVRHeadset.cs b/Assets/VRTK/Source/SDK/SteamVR/SDK_SteamVRHeadset.csindex d54988d..3e59f49 100644
--- a/Assets/VRTK/Source/SDK/SteamVR/SDK_SteamVRHeadset.cs
+++ b/Assets/VRTK/Source/SDK/SteamVR/SDK_SteamVRHeadset.cs
@@ -133,7 +133,9 @@ namespace VRTK
         /// <param name="fadeOverlay">Determines whether to use an overlay on the fade.</param>
         public override void HeadsetFade(Color color, float duration, bool fadeOverlay = false)
         {
-            SteamVR_Fade.Start(color, duration, fadeOverlay);
+            // PATCH: SteamVR_Fade is also broken in LWRP ~krzys_h
+            //SteamVR_Fade.Start(color, duration, fadeOverlay);
+            VRTK_ScreenFade.Start(color, duration);
         }

         /// <summary>

(and then add the VRTK_ScreenFade_LWRP on the camera manually so that VRTK doesn't automatically add the other one)

[Manuel-Meyer]

The Solution above doesn't work for me (Unity 2019).

IAfterRenderer is not part of UnityEngine.Rendering.LWRP and LightweightPipeline is not in namespace using UnityEngine.Experimental.Rendering anymore. Has anyone found a solution for this problem?

[huseyingulgen]

Does not work for me also. I just use ui image for fade now. It is not working well but you can use for now. If somebody has better a way , They can share solution here for LWRP please ? @Manuel-Meyer @krzys-h

[krzys-h]

I'm pretty sure Unity 2019 moved UnityEngine.Experimental.Rendering to just UnityEngine.Rendering.

Anyway, as it later turned out my solution didn't work on the actual headset for some reason, only on the simulator - I ended up switching to directly calling OpenVR.Compositor.FadeToColor() which worked even better for my purposes (fade between changing scenes - Unity would sometimes hang while loading and drop out to the compositor, this way the compositor keeps the screen black even if Unity stops rendering for a moment). Of course that is only valid when you are using OpenVR, but I guess other platforms must have something similar.

            try
            {
                if (OpenVR.Compositor == null)
                    throw new Exception("OpenVR not available");
                OpenVR.Compositor.FadeToColor(0.75f, 0.0f, 0.0f, 0.0f, 1.0f, false);
            }
            catch(Exception e) // throws the exception above if OpenVR is disabled or "dll not found" on platforms that don't support it at all (anything Android based like Oculus Quest or GearVR)
            {
                // TODO: add some fallback here, I'm just calling the VRTK fade for now to have it look correct when testing on the simulator
            }
            yield return new WaitForSeconds(0.75f);

            AsyncOperation asyncLoadOp = SceneManager.LoadSceneAsync(sceneToLoad, new LoadSceneParameters() { loadSceneMode = LoadSceneMode.Additive });
            yield return asyncLoadOp;
            if (previousScene.HasValue)
                yield return SceneManager.UnloadSceneAsync(previousScene.Value);
            SceneManager.SetActiveScene(SceneManager.GetSceneByName(sceneToLoad));

            try
            {
                if (OpenVR.Compositor == null)
                    throw new Exception("OpenVR not available");
                OpenVR.Compositor.FadeToColor(0.75f, 0.0f, 0.0f, 0.0f, 0.0f, false);
            }
            catch (Exception e)
            {
                // TODO: add fallback here
            }
            yield return new WaitForSeconds(0.75f);

[cocapasteque]

Any ETA for this issue ?

[bddckr]

We'll not look at SRP support before Unity stabilizes that functionality. Additionally Unity currently does offer no way to support multiple SRPs in a single codebase/package.

You can observe changes to this issue to know about the progress on this.

[thestonefox]

Some further work has been done on this in the PR #477

But it's still not working on Oculus Quest so still not ready for merge.

[thestonefox]

Proposed solution https://gist.github.com/hawkwood/41b0b361fdfa7a14acd21ae4a571f4dc

[thestonefox]

PR with fix

#543

[ExtendReality-Bot]

🎉 This issue has been resolved in version 1.36.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• v1.36.1
• GitHub release

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