Render texture optimizing (removing depth prepass ?) HDRP

Hello,

I'm using 8 cameras going into render textures. Theses render textures are really having a high impact on the game framerate. I'm running at 70fps and fall to 40fps with the cameras activated.

The cameras are only rendering simple flat 2D objects in orthographic mode. I then use the resulting textures as alpha masks. So I don't need hi quality graphics from theses cameras. I've put the objects being rendered on their own layer used as a culling mask for the cameras. I deactivated every possible rendering option apart from "opaque objects".
But nothing seems to help. I also changed the resolution of the textures, but that doesn't seem to have any impact.

I then looked into the output of the profiler and discovered the "mask cameras" as I call them, are using a fair part of the CPU cycle. Under inspection, the "depth prepass" is taking the longest and I don't really know how to remove it.

I'm running on Unity 2019.2.11 with HDRP 6.9.2

Any ideas ? It feels near unusable to have render textures at that cost !

 

Enable Custom Frame settings on those cameras and turn off depth prepass.

 

Unfortunately this option is already ticked off. I really don't understand why this depth prepass is still taking place.

 

Yes, I just have two unlit objects. One is a simple "background image" (unlit opaque) and the second one is a custom shader graph. It's very simple, just a simple unlit and a noise to create a displacement type effect. I use theses to create a texture mask for my character (the cutout for eyes and mouth). The shader graph is used to displace the mouth of the character when he is afraid.

 

did you ever find out how to minimise depth prepass?

 

There is a gotcha where you need to turn of decals in order for the depth pre-pass to be disabled. Supporting decals forces there to be a depth pre-pass regardless of any other settings.

 

thanks! that makes sense, shame though that will be footprints and bullet holes gone I think. Will try it, cheers again.

 

From what I tried, even a single extra camera is not even close to acceptable performance wise even with every feature turned off in the custom settings, no matter which resolution, unless you render the camera only X times per second

The fixed camera costs are just too high

You could try do a custom render texture which gets its data without any camera. Its not as easy but you skip all camera performance costs.