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so that the grass particles don't go through the wall of my building, I used a boolean modifier to get rid of most of it inside the building, but there is still a little left. enter image description here

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  • $\begingroup$ Can you place a more readable image or Blender screen capture in addition to your original image? Please show a close up view of the problem. Please show the mesh on which the grass is generated. A closeup view of just the problem area in addition to your original problem. I see the large portion of grass around the building. In addition I see the curvy green narrow line. I am not sure which area is the problem. Perhaps you can also label areas ... good/bad ... success/failure. GIMP is a free image editor. Blender has Text Object. $\endgroup$ – atomicbezierslinger May 17 '19 at 19:07
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Use weight paint to limit grass particles near the wall of your building.

enter image description here

Weight Paint mode. Hair is yellow. Red to Blue gradient. Red areas specify the most hair. Blue areas specify no hair. Gradient between Red and Blue specify values between the two extremes. The Yellow arrow in the Vertex Groups Panel of the Particle Tab shows the vertex groups selected for Density and Length.


Meshes with hair/emission particles can use weights produced by [weight paint] mode. Then hair will be produced in certain areas. This produces vertex groups. The particle system [density under vertex groups] can respect the vertex group. Some areas can have hair or grass. Other areas can be excluded from grass.

Your model must have enough vertex density for fine detail. Please click on image above to see higher resolution closeup of the image. The vertex vertex denisty will be more readable.

For example. Eyelash areas on a face can be weight painted.

So you could weight paint your mesh and exclude areas too near the building wall. If you have only a still photo image and not a moving image you can be less precise.

Perhaps related

How do I make a section of hair a different color?

This is not a tutorial on weight painting .. yet other questions here at BSE and the video web site that has a name that rhymes with newnube cab be searched.

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