Issue with Render to texture targets

Hi everyone,
I’ve got an issue with render targets, and at this point I am not sure if there is something wrong with my logic, or a deeper issue with the order of how the engine renders texture targets. Let me explain:

I am making an utility to generate spritesheets in runtime, from a camera rendering some sort of chroma boxes. Here is how it is supposed to work:

  • There are two render targets, one used to render the scene in the chroma box (RT_CaptureCam), and one used to make the spritesheet (RT_SaveTextureToBuffer)

  • The material that has the spritesheet logic scales the RT_CaptureCam, then masks the correct sprite index, and then combines it with the RT_SaveTextureToBuffer RT. Here is the last bit (the sprite index logic works fine)

  • The Blueprint running this setup also periodically (determined by capture resolution and duration) a function that basically updates the material, then updates the RT_SaveTextureToBuffer RT with a drawn to texture version of the material:

  • My expectation is that, if a material combines the RT with the RTbuffer, and then updates the RTbuffer with the result (B = A+B), it should accumulate over time

However, when I run it, this is what I see:

(The plane on the left has the material shown in the shot above, the one on the right only displays the updated buffer)
Any ideas? Like I said at the beginning of the post, I think my logic is solid but I might have been looking at this for too long

Much appreciated

It seems that the buffer update happens before that RT gets added to the processed capture (notice how the image on the left plane appears brighter)… no sure why, or how to fix it though :frowning:

Been experimenting some more: Updating the buffer before updating the material makes it render the last two frames (N and N-1), but still doesn’t accumulate over time.

Bump. Any help?

Bumping again, in the hopes that someone figures it out