Particles not emitting in the correct direction...

Hi… I was not able to address this in the Works In Progress forum so I’m going to try here. I am trying to create a light fuzz type of look for a flower stem using the particle system in Blender. I’m using the Blender internal rendering engine. I am able to create the effect I want as shown in the image below:


I can do this as long as I don’t bend the stem. The straight stem on the right has the exact effect that I want and I had no problem getting that look and even better on a straight stem. The problem I’m running into is that when I bend the stem, the particles don’t emit properly. I’ve recalculated normals but this has not helped. I tried replacing the cylinder with a cube and subdivision surface modifier… same result. As long as the cube extends straight, things look good, but bend the cube and the particles go berserk.

Any ideas on what I could do to get the look on the right to work with the bent stem on the left?

The following image shows a more clear picture of the difficulty… although this 3dview and I set the length of the children to be longer than I want, the pic does provide a clear view of the issue:


Any guidance would be greatly appreciated.

Thanks,

Brett

How are you bending the item? If you are using a modifier, be sure that it is above the particle system in the stack.

To bend the cylinder I added about 5 loop cuts and then rotated the segments in edit mode and used the smooth option. I’ll try a curve modifier and put it above the particle system in the stack. Thanks!

Is this what you want, more or less? hairs enlarges for clarity…If this is what you want it’s pretty simple to do with a hair system, let me know. I can post a couple steps and screen shots. If not explain it more.


Yes… that’s what I’m going for. The original pictures are using a particle-system/hair setting. I’m finding that I like a larger number of parent strands (not visible) and a smaller number of child strands. It’s definitely giving me the look I’m going for. The problem I having is that when I bend the cylinder as mentioned above, the strands emit in the wrong directions. I’m in the process of trying a curve modifier to do the bend, although I’m not certain that is going to address the problem. I’m hopeful.

Using a curve modifier is showing promise. A very quick test produced reasonable results. The strands are not as straight as those shown above, but it may be the way I manipulated the Bezier curve. I’ll keep at this. I think this is going to work.

Well I threw together some screenshots of how I made it. I feel like there’s a way to do it without rotating the strand in edit mode and it’s definitely hacky and probably incorrect, but it does work., but you may find that your answer lies in rotating your stand (in edit mode) so it is parallel to the y axis with the tip of the hair pointing towards positive y, and the origin is at the base of the strand (see image). I’ll post a link to the image on my server, since b.a. will shrink it down too much. But you can probably make in in 10 minutes or so and even keep your objects. Let me know how it turns out, and post some renders if it works.

http://www.slogobox.com/blenderfoo/hair-on-plant-tut.jpg


This looks great!! I’ll follow these steps and see what I can produce. Thanks!!

Hi… I felt comfortable with everything you put in the steps you outlined for me but I am still getting a similar result as the other approaches I’ve tried. Here is a snapshot of the model in 3dview. I positioned the view so it more clearly shows that my output does not look like what you specified in the 3rd picture of your steps. (Should look like image on the left). Mine is rotated a little to show that it doesn’t.


This is the result I’m struggling with in all other instances. The strands (or modeled hair in this case) do not distribute evenly across the curved (extruded circles) object.

This is very confusing. I did start to get reasonable results using a curve modifier on a cylinder object. I’m using Blender 2.65. I also recalculated my normals when I did not get the results I was expecting. Made no difference. I’ll keep at it.

I think I’ll go with the use of curve modifiers for the stem fuzz. Here’s a sample of the difference between what I started with and the result I’m getting when I bend the cylinder with a curve modifier…


Any comments or suggestions are always appreciated.

Thanks,

Brett

Hmm, that is strange. When I use a curve modifier I get the same results. Even if I apply the modifier and recalculate normals it does the same thing. Looking at the normals themselves they are fine. I think it has something to do with the mapping of global to local on the modiifer, don’t really understand that stuff at all. Well I’ll post the blend I have using an extruded circle which behaves normally (pun indended!) I am working in cycles and you should try it too, the blend file is cycles. The lights are 2 planes with the emission (light) material. The plant/fuzz materials are both simple diffuse. As you can see in the image, you can preview your render, without actually having to render it, by clicking on "Rendered. Give it a little time in order to see a decent render, it isn’t instant. Good luck, post some renders if you get it working.
http://slogobox.com/blenderfoo/plant-hair-web-12.blend


http://www.slogobox.com/blenderfoo/green-hair-with-cycles-screenshot.jpg

The reason this is most likely happening:
Normals calc and children,
The best way to fix I believe would be to apply the curve and then recalculate the normals, then see.
if that doesn’t work, then you need to make sure you are using children that are interpolated and that dynamic rotation is turned on for the parent particles, if even that fails then you may want to look into another way of doing that, but I think it’s most likely normal cauluations not updating or the dynamic rotation not being applied.