Particle systems (cause we love them!) - rotation

So I am making a game, with the graphics in blender, and I have came across a problem regarding hills. So i need a grassy hill, without any bare patches. When you create a hair particle system, I suppose it uses the rotation of the part of the mesh it is emitting from, but when viewed from above, you cant really see the grass, just the emitter with a Soil texture, because the particles are so small. When viewed from the side, it looks good, like real grass. So I tried to hide the texture by making the grass have a lot of brownian, but it looks all squiggly. I then thought that it would look better if I could do this (picture):


So basically I need to constrain the emission to be on the Z axis, but I cant figure out how. Please help.:frowning:

Thanks.

Are you using particles or hair?

  1. In hair particles, top is towards y so you have to rotate your instances (and apply rotation) accordingly. Two different coordinates systems: my idea of consistency and user friendliness.
  2. When you crank rotation up to max, you would expect instances to rotate up to 360 degrees. Wrong, they rotate up to 180 degrees so you have to duplicate the mesh and rotate one of the copies by 180 degrees. How this bug escaped developers for time immemorable is beyond me.

I was using a hair particles system, rather than an object because it has 30000 blades with 300 children each, and a mesh would be too many vertices! I was using hair particles so that the vertex count was low, but I need to find a way to make them lock to the axis

Hair objects are instanced, the number of total polys is pretty much meaningless. If it’s causing viewport issues, there are a number of things you can do, like drawing the objects as bounding boxes, reducing the number of display children, reducing the display %, displaying particles as points intead of rendered object, etc.

Apply rotation of emitter object, turn on advanced settings, under velocity, set normal to 0 and emitter object z to 1

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@11jlyness
For such stuff my addon is very handy.
You can sketch assets onto the surface. With a slider you can also set how much you want to align the assets to the ground normal.
Take a look at the addon and video. Maybe this could be a time safer for you.