Yes, with weight painting in particle mode. It’s not drawn correctly, so you have to guess the weights.
BTW, the root keypoint of a hair particle always has a weight of 1, the tip by default a weight of 0, there should be linear interpolation between these two values (though I don’t think it’s linear, but there is some kind of interpolation).
Can anyone confirm here whether also other particles types (not just hair) will be eventually editable? As it was in first WIP versions of new particles system?
With this functionality we can use PaintFX in Blender as was shown in this great Blender video tutorial http://www.coyhot.com//Blender/Blender_PaintFX.7z made by CoyHot.
Could you be more specific about how to enter Weight Painting from Particle Mode? If I simply select Weight Paint from the mode list, it doesn’t seem to allow particle painting. My situation’s a little complicated by having the emitter mesh also a soft-body – I use the mask feature to keep from re-painting the mesh weights for the same vertex group.
That doesn’t jibe with the results I’m getting – the hair particle strands behave as if the Use Goal : G Min Value is the weight for the entire strand, no differentiation along the length. Example: if I specify Gmin = 0 and GMax = 1.0 (theoretical range of the strand), the entire system acts as a “free” soft-body, the root keypoints do not follow the motion of the Goal vertex group.
You need to UV map the image to the subdivided polys. Then each piece of the image should follow it’s respective poly around.
No no, you have to set the hair “Set editable” and paint in particle mode with the “Weight Hairs” brush. Change to “point select”
http://wiki.blender.org/index.php/Sandbox/Particles-Particle_Mode
The strength of the brush is the weight.
This should not happen. Maybe you try it at first without making the mesh a softbody?
Edit: Hair softbody on softbody objects is seriously broken. This needs to be fixed (or disabled).
Ah, the lifting of the veil! I hadn’t found that sandbox link yet, thank you very much. I hadn’t known what the “Weight” option was all about in the Particle Properties pane.
BTW, when using it, I do get a grayscale rendition of the weight from Black=0 to White = 1.0, so it’s not nearly as much guesswork as I’d anticipated. And now the Goal weight range for the s-b is acting much more as expected. I think somehow all the weights in my system were set to 0.50 (it appeared medium gray along the entire length when first opening the .blend)), though I’d done nothing to alter the weight (didn’t know how).
“Small steps, Elly.” 
Thanks again.
My edit in response to your edit: OK, I’ll make two objects, one a s-b mesh, the other just the particle emitter. Shouldn’t be too difficult. Shouldn’t be… 
BTW, when using it, I do get a grayscale rendition of the weight from Black=0 to White = 1.0, so it’s not nearly as much guesswork as I’d anticipated. And now the Goal weight range for the s-b is acting much more as expected. I think somehow all the weights in my system were set to 0.50 (it appeared medium gray along the entire length when first opening the .blend)), though I’d done nothing to alter the weight (didn’t know how).
Weight painting is a bit different than you’d been describing, about painting weight on the length of the hair. Weights don’t correspond to hair points, but rather to full hairs, so it’s not that the weight is 1 at the root and tapering, exactly.
Rather, it seems that the weight basically controls how much the tip of the hair displaces with the soft body simulation. The length of the hair moves freely no matter what. If you set the weight to one, for example, the tip won’t move at all, but the hair between the tip and the root will still move freely with the soft body sim.
This surprised me a bit at first, but in my experiments it resulted in very intuituitive behavior for hair, and the weighting was quite unnoticeable the final animations. You can control the movement of the hair as you’d like too, but (and this is a good thing) you don’t wind up with a bunch of motionless hairs on your character’s head.
If you do want motionless hairs, I think the right way to do it would be to mix two particle systems.
@ bugman: Hmmm. If this is the case, then why is it apparently possible to paint weights along the length of the strands in a non-uniform manner? It seems in my tests that the strand response is modified by doing this, and I can restrict the soft-body response along the strand length much the same way weight painting for a s-b mesh is restricted.
I’m sure the gory details are beyond me, but I do seem to be getting the control I was searching for. I now have a set of strands that deforms in good synch with a soft-body mesh. This allows me to use a relatively small number of parent strands to form the hair mass’ surface, and not have to render a huge number of child particles, which is not only very impractical with YafRay, but also chokes my comp pretty badly.
@ bugman: Hmmm. If this is the case, then why is it apparently possible to paint weights along the length of the strands in a non-uniform manner? It seems in my tests that the strand response is modified by doing this, and I can restrict the soft-body response along the strand length much the same way weight painting for a s-b mesh is restricted.
Interesting. You’re right. This has changed since the build I experimented with. Thanks for the heads up!
so, weight is like … flexibility? or stiffness? with higher weight, the hair strand is more stiff?
So there can be different weights up and down the strands now? Interesting what that will lead to.
@ Papa & CD: Far as I can tell from my tests, Weight in the Particle Edit Panel is used to modulate how the particle strands act when they are given soft-body status. As with meshes, you can specify a vertex group that acts as the soft body Goal. This vertex group can be associated with a bone, so the bone can control the soft-body hair strands. The Weight on the strands then determines how much control is from the vertex group and how much from the s-b simulation.
There are other soft-body parameters that seem to act on hair strands very much like they do with a mesh – the Goal & Edge sections both have Stiffness fields, as well as Rigidity, that can be used to finesse the actions of the strands. Tech details you’ll have to find elsewhere, I’m just now after hours of trial & error getting the barest sense of what does what, and that mostly with my own goal in mind, which is fairly specialized, so I haven’t done a broad series of tests.
EDIT (hours later)_____
This thread’s about understanding the new particles, but I don’t understand what has happened. The hair particle system I spent hours tweaking to perfection (well, close enough) has suddenly stopped acting like… anything. I can’t comb it, can’t weight paint it, can’t change strand lengths, it no longer acts like a soft body though it’s still set up as one. All I can do is Cut the strands.
Only change is I added another hair system to a different mesh for the rear of my model’s head. Luckily I have an incremental save fall-back, and recovered 99% of my work by appending, but does anyone have any idea why the hair system would wig out like that? (Yes, pun very much intended :D)
Yes, the weight defines the goal value. The weight is painted along the hair particle (as I’ve described on mediawiki).
It works exactly the same way as with meshes (to be more precise: as with softbodys for curves). The stiffness defines the force that bends the keypoints to their original position, you can scale the weight values with GMin and GMax, EPull and EPush defines how much a hair may change it’s length, Bend defines the rigidigty over two segments.
I’ve been using the new particles for a while now and love them! I’m trying to make some smoke though and I need to use fields for this. The fields work (I’m using spherical and wind) but when I enable MaxDist and set it to the right distance the field stops working completely. Is this a bug or I’m I just missing something?
Regarding the hair again: Has anyone else noticed that the Rad and Clump/Shape values are applied asymmetrically? I have an emitter mesh that is X-axis symmetric. Adding parent strands with X-axis editing symmetry enabled works fine. I remove all doubles. When I add children using the Particle spawn option, those on the right side of the mesh (-X) are more broadly spaced apart for the same Rad value as those on the left (+X). This affects the results of the Clump and Shape values as well, leading to a significant asymmetry in the volume of the hair, the right side looking “fluffier” (more space between strands).
This occurs with all three SVN builds I’ve tried it on.
I haven’t found anyplace to submit bug reports on SVN dev builds, however, unless it’s on the regular Bug Tracker?
That’s the current theory. But as you add rotation to the piece, the texture stands still while the piece rotates.
Strange it be.
Love the paintFX video