Question Particles don't render via CommandBuffer

I'm trying to render particles with a CommandBuffer.DrawRenderer() (HRDP) and particles don't update even with "Always Simulate". I'm emitting them via ParticleSystem.Emit(). But they are not actually updated and drawn. They appear only when i switch to Scene Camera. Then Frame Debugger starts to show my commandBuffer, and last Scene-view state is drawn by it, but particles they stop updating the moment i switch to Game. The version is 2019.3.7f1
Those are Billboard with View alignment and Always Simulate:



Am i doing something wrong?

 

I "fixed" it by adding useless copy of my main camera and assigning it the same layer as the particles. Then manually rendering it with cam.Render() into a useless renderTexture just to trigger particle updates.
Then i do my commandBuffer.drawRenderer(particles) and it works fine (if you can call it that)... in 2019.3.7f1.

But if i "upgrade" to 2019.3.8f1, it does not execute the command buffer again even with this workaround. This is very frustrating.

Can anyone help me understand, why particle render via CommandBuffer.DrawRenderer does not work as intended?

 

Probably worth poking @richardkettlewell as well as filling a bug report.

 

I've had the same issue in URP. DrawRenders is fairly broken since it was introduced. For example, trying to draw a disabled trail renderer flat out crashes Unity.

Like you said, particles only render correctly when the scene view camera renders. I got around this by baking the particle system to a mesh, and drawing that instead. This is arguably a little slower, but the only thing I found works.

Code (CSharp):

1. if (!bakedMesh) bakedMesh = new Mesh();
2. m_ParticleRenderer.BakeMesh(bakedMesh, renderingData.cameraData.camera);
3.  
4. bool localSpace = b.particleSystem.main.simulationSpace == ParticleSystemSimulationSpace.Local;
5. cmd.DrawMesh(bakedMesh, localSpace ? m_ParticleRenderer.localToWorldMatrix : Matrix4x4.identity, material, submeshIndex, passIndex, props);

 

I hope to find time to make a project for a bug report.
@richardkettlewell, please help?

Thanks, i'll try the BakeMesh approach. I want to use trails with my CommandBuffer system too. What if trails won't be disabled, but will be in a layer, that is not rendered by main cameras (only a dummy one)?

 

Not sure if that'll work as well. In my case, trails only needed to be rendered to a specific camera using DrawRenderers. Leaving them enabled and setting the forceRenderingOff property on the TrailRenderer made them invisible to everything else, which worked for me.

But I still had to bake trails to meshes since the scene view camera influences how they're rendered for some reason.This was in URP, but I assume this is the case for HDRP as well.

Code (CSharp):

1. m_TrailRenderer.BakeMesh(bakedMesh, renderingData.cameraData.camera, false);
2.  
3. cmd.DrawMesh(bakedMesh, Matrix4x4.identity, TrailMaterial, 0, 0, props);

 

Actually, this is not a bug. when rendering particles, the camera is required, but in the srp when using commandbuffer DrawRenderer rendering particles, the camera may be null. So the particle renderer is not working.
The solution is simple, add Camera.SetupCurrent(camera) just before commandbuffer rendering particles.

 

While the undocumented function Camera.SetupCurrent makes the particle system render, it seems to break the projection for VR rendering and the image is distorted.

 

Unity sent word that this bug (yes it was a bug) is now fixed in 2022.2.0a3