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Trails that don't Die with Particles evolve oddly

Discussion in '5.5 Beta' started by ScottPZ, Nov 30, 2016.

  1. ScottPZ

    ScottPZ

    Joined:
    May 26, 2015
    Posts:
    6
    Thanks for adding Trails to particles! This will be a fantastic addition to Unity particles.

    I'm making smoke trails for explosion particles, and I'm having an issue with particle trails that have "Die with Particles" disabled.

    Currently, the evolution of the shape of the trail changes dramatically after death that doesn't match how the trail starts forming at the beginning of its life. Any of the "... over Trail" and texture UV parameters make the trails appear to hit a wall and scale down after the particle dies, instead of continuing their motion. Also, I've noticed that the apparent frame rate appears to slow down after the particle dies, as if it's updating only every other frame or even less frequently. I think I understand the problem, and I would like to propose a solution.

    Here is the problem. This image represents a particle at time of death and the same trail about halfway after death.
    trailDieWithParticleA.png
    Notice that the scale at the head stays the same over time as if squashed rather than "playing out". The overall "Width over Trail" seems to be simply parametrically attached to the trail curve. I propose that you factor in the time after the particle dies into the parametric space of the trail after death.

    Here is what I expect:
    trailDieWithParticleB.png

    I've submitted a bug report, but don't have the tracking number yet.