How to change particle material in mid-animation?

I want a Belgian flag to transition into an American one through keyed halo particles. The animation is ok but the materials mess up.

I have 3 objects: a Belgian flag, an American flag, and a cube. The flags are rectangles with their own flag texture, UV-mapped. The cube is a control object for keyed particles. I’m using Blender Internal.

Both flags share the same particle system: 3000 particles, Start frame 3, End frame 3, lifetime 15000, No Rendering, no gravity influence.

The cube has a particle system with Keyed particles, 3000, Halo rendering, Keying set from ‘Particlesystem:Flag1’ to ‘Particlesystem:Flag2’.

The particles fly nicely and the animation is good. The problem is the material. When the particles fly from Belgian to US flag, their material should change respectively. This is not the case. I have tried doing this by adding both flag textures as materials to the control cube, then using a keyframe (in the Particle Settings > Render tab) from material 1 to material 2. The following problems occur:

  1. The materials don’t blend smoothly, but change very abrupt. Keyframe 1 is set at F30, KeyFrame 2 at F60. Instead of a 30-frame long blend, the material suddenly changes at F45.

  2. The flag textures lose their UV-maps. The keyed particles append the color from the flag textures, but NOT the shape, eg the belgian flag consists of black, yellow and red particles all over the place, instead of a Black, Yellow and Red stripe.

Does anyone know how to solve this problem? I’m using Blender 2.69 Official on an HP Pavillion dv7 laptop with Dual core 2.16 Ghz and 4 GB ram. Windows Vista 32-bit.

Many thanks!

well a bit of info might help. how exactly are you using halo particles to affect a transmission. what is the cube doing? cycles or BI.
just saying something is wrong isn’t very helpful
form what you say everything is doing what you have told it to do so, more info = more help

Sorry about that :slight_smile: I should not have posted this at 4.00 AM :p. Information has been added now! I hope I didn’t forget anything.

You could use one material and cross fade the textures. Add both flag textures to a single material. Set the first flag’s Color influence to 1.0 and the secons flag’s Color influence to 0.0. Then keyframe a crossfade between the Color influence.

Hello Atom :). What you said is what I tried right after submitting this post. The transition is smooth, but the texture mapping is messy. It does not respect the UV-maps I made on both flags.

i’m still not clear on what you are trying to achieve. :confused:
are you using two flags but trying to make them look like one flag that changes colour as the particles pass? or is there two flags that smoothly change? or are the flags becoming the particles and then remaking themselves into new flags? :spin:
or am i understanding that you have two blank flags and the colour is made up of particles that you want to transition as they fly between flags??