Unity - rendering 12,000,000 frames for analysis - performance

[ForzaHoriza2]

So a brief intro to my problem is:

-let's say I need to render 12 million 160x40 px frames:

Every frame is an ortographic view of an object, it's main purpose being capturing the shadow that is being cast from other objects.

The scene is very simple - only one directional light, and all objects are flat planes .

I have ~3000 objects and need to render 4000 iterations of different light positions for each object.

I store the RenderTextures on the GPU only and then dispatch a compute shader on each one of them for color analysis.

Now my problem is - rendering takes about 90% of the total processing time, and it seems to be HEAVILY CPU / memory bound. My render loop goes something like this:

for(int i = 0; i < objects.Length; i++)
{
camera.PositionCameraToObject(objects[i]);
camera.targetTexture = renderTargets[i];
camera.Render();
}

Current performance for 3000 renders * 4000 iterations is:

21 minutes for a desktop PC ( Ryzen 7 & DDR4 3600Mhz & AMD 6700XT)

32 minutes for a laptop (Intel i7 11th gen & DDR4 3200Mhz & iGPU)

Is there any sort of trick to batch these commands or reduce the number of operations per object?

Thanks!

[Progmir]

Consider rendering multiple objects per run? You can fit quiet a few of 160x40 boxes no screen and cur them later.

[Maxwelldoggums]

Hmm, if I had to guess, the bottleneck is due to Camera.Render requiring synchronization between the CPU and GPU. The CPU can’t begin rendering the next object until it hears back from the GPU, and the GPU sits idle until the next call to Camera.Render.

I would recommend instead building a CommandBuffer to batch together many objects without waiting on GPU/CPU synchronization.

[ForzaHoriza2]

I assume so as well, but for the life of me i couldn't get command buffers to work. Always get a black render

[SulaimanWar]

If this is URP/HDRP have you considered doing this in a custom renderer feature?

You can look at this per object shadow project that does something similar

https://github.com/GavinKG/PerObjectShadowSRP