Algorithm of vegetation

Scripting Issues
1

Hello, I try to insert the 3d grass around the player and removed when the player is too far.
But my program is not optimized…

Are you there a more optimized way to do this ? Is there already a specialized API you ?
after I want to dynamically insert 3d grass, 3d tree…etc and remove when player is too far.

	def InitVegetations(self):
		VisibilityVegetation=100
		VegetationMatrice = [[0] * VisibilityVegetation for _ in range(VisibilityVegetation)]
		while 1:
				for i in range(0, VisibilityVegetation):
					for j in range(0, VisibilityVegetation):
						if VegetationMatrice[i][j]==0:
							
							m = loader.loadModel("resources/grass/grass.obj")
							m.setScale(.2)
							pos1=player.getPos()
							
							min, max = m.getTightBounds()
							size = max-min

							x=pos1[0]+size[0]*i
							y=pos1[1]+size[i]*j
							
							m.setHpr(0,90,0)
							m.reparentTo(render)
							m.setPos(x, y, 0)
							height=self.GetHeight(m)
							pos2=m.getPos()
							m.setPos(pos2[0], pos2[1], height)
							VegetationMatrice[i][j]=m
2

The most efficient method to render vegetation is probably using instancing combined with some LOD algorithm.
As for that, I also have some code lying arround, but its outdated and won’t work anymore, so it would be quite some work to make it running again.

3

My question is how optimize the load model, because in my code i load model in loop:

for i in range(0, 10):
   m = loader.loadModel("resources/grass/grass.obj")
   m.reparentTo(render)

I would not charge the same grass every iteration for example:

m = loader.loadModel("resources/grass/grass.obj")
for i in range(0, 10):
   m.reparentTo(render)

But with this code i load 1 object not 10.

4

Have a look at instancing: https://www.panda3d.org/manual/index.php/Instancing

This is not as efficient as instancing on the GPU, but should already improve the performace.

5

Can i instanciate on the gpu with panda3d ?

6

Yes, you can do so by calling model.set_instance_count(num_instances). However, you will have to write a shader then which positions your objects (since they otherwise will be all at the same position).

In your shader you can access the current instance id with gl_InstanceID. You would have to pass some sort of array (e.g. a PTALVecBase3f storing positions of the instances) as shader input, and use that in the shader then.