I have been following the blender guru tutorial on creating sparks using the particle info node to divide the particle age by the lifetime to produce a ratio - which in turn feeds into the material making the particles fade based on how old they are or how far away from the emitter they are. I then tried to recreate this “slo mo” effect and ran into some problems.
I used the time remap function on the render settings to remap the animation to slow it down and it had the desired effect on the particle motion - however it seems to be having an odd effect on the materials.
Without remapping the time value - the particles fade based on their age as expected - i.e. the particles fade the further away from the emitter they are - but do so consistently throughout the animation showing that each particle is aware of its age (these three screenshots are taken from frames 1, 20 and 40 of the animation respectively)
If I remap the time value to slow the animation by half (old time = 50, new time = 100) - I get the following output for frames 1, 20 and 40 (see next post)
I dont understand what is happening here. The first frame looks ok - but it appears that the output of the division calculation changes over the course of the animation meaning that by frame 40, all of the particles that are being emitted think they have already exceeded the lifetime and thus are applying the “faded” part of the material. Its almost as if the particle age information isn’t being passed to the particle info node if you apply time remapping and it therefore assumes all the particles emitted have an age based on the start of the animation, rather than the time each particle was actually emitted.
Can anyone suggest whether I am doing something wrong - or could this be a bug?
(Actually - this thread would probably sit better in the materials and textures section).