I’m using 4.13 new feature which allows me to render to RenderTarget from a blueprint. It works great most of the time, except for one strange thing.
What I do:
- on begin play: clear render target to black (do not clear RT on tick!)
- on tick first: rendering the quad over the whole RT using transparent mode with color like this (0,0,0,0.01) (i.e. it will darken the whole render target slightly)
- on tick then: render some moving textures using transparent mode (i.e. similar to moving particles)
- result: moving sprires will leave small trails behind which will be faded out eventually due to blending with (0,0,0,0.01) color every tick
Basically it works OK, however only when HDR option is enabled in RenderTarget settings. The format will be FloatRGBA in this case. But I don’t need any HDR, I need regular color, so I disabled HDR. This is where things start to break. Now I see unexpected huge trails behind my moving textures which decay very slowly. I’ve tried many formats of the RT, but trails persist if HDR is disabled. Enabling HDR makes RT a lot bigger in memory, so not an option.
Corrent version (with HDR)
Wrong version (without HDR)
Which options I need to check if I want simple rendering to non HDR, non sRGB render target since the data in render target is not a regular color, but will be used for further processing?