• Boris FX Particle Illusion

  why some particles don’t work well with image alphas

  Posted by Edward Porter on January 14, 2007 at 6:20 am

  I am trying to something I assume is quite basic. Have an emitter display is animation within the confines of a simple alpha shape (a very simple logo). I followed Elvis’s ‘charmed’ orbing tutorial and disintegrating logo tutorial for learning how to do this. Using the ‘orbing cover’ emitter with ‘get transparency from layer’ & increasing the ‘number’ property I was able to get a vague shape of my logo. However, it is only vague. The emitter decidedly spills beyond the confines of the shape of my logo. Why is this? Worse, trying this same technique with some other emitters (an example would be the emitters from Oct.’06) the emitters seem to almost ignore the logo alpha altogether. To be sure, the alpha is doing something with these emitters, their behavior is affected by the alpha, but the result is certainly not that they only appear within the confines of my alpha.

  What is the property of an emitter that allows it to animate beyond the confines of an alpha? Is there some ‘randomness’ property? (if so I haven’t spotted it). I have tried using ‘mask emitter with image’ which seems to work no better.

  thank you in advance for any help or input,

  Edward Porter replied 19 years, 4 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Alan Lorence

  January 14, 2007 at 1:27 pm

  You’re using the wrong feature. You’re using an area emitter mask, which is used to define where particles are created only. Does nothing to restrict the particles after they are created.

  You need to look in the docs for the section on bg image transparency, particularly “use image as stencil”.

  Alan.
  wondertouch
• 

  Edward Porter

  January 16, 2007 at 1:56 am

  Thanks so much. I just tried the stencil option & it works perfectly. Just what I was looking for.

Reply to this Discussion! Login or Sign Up