# how Gencase create Cartesian Lattice node

Hi

i try to simulate DaulSPHysics and use external STL to create initial boundary particle.

i search for few documentary and they said Gencase create Cartesian Lattice node first.

and identify which node inside of STL(obj, vtk etc). and create particle at that nodes.

so i wonder how Gencase create Cartesian Lattice node.

during test, i notice Cartesian Lattice node always take (0,0,0).

any documents tell algorithm of Gencase to create Cartesian Lattice node

## Comments

Please check https://github.com/DualSPHysics/DualSPHysics/wiki/5.-Running-DualSPHysics#54-preprocessing

and figure 5-7:

"GenCase employs a 3-D Cartesian mesh to locate particles. The idea is to build any object using particles. These particles are created at the nodes of the 3-D Cartesian mesh. Firstly, the mesh nodes around the object are defined and then particles are created only in the nodes needed to draw the desired geometry. Figure 5-7 illustrates how this mesh is used; in this case a triangle is generated in 2D. First the nodes of a mesh are defined starting from the maximum dimensions of the desired triangle, then the edges of the triangle are defined and finally particles are created at the nodes of the Cartesian mesh which are inside the triangle."

thanks Alex, i check the article you mentioned

the reason i asked previous question is that "Whether 3-D Cartesian mesh is fixed or not regardless the simulation setup(especially about geometry)"

i do some test with StillWedgeLR case. and i conclude that "3-D Cartesian mesh is fixed regardless of geometry setup"

here is my setup and the result of boundary particle(Normals.vtk) and hdp.vtk(BlueLine)

if 3-D Cartesian mesh is adjustable to my geometry setup, both cased have no gap

but move x=0.01 makes gap. and i guess probably the reference point of 3-D Cartesian mesh is (0,0,0)

from this test, i feel when i setup geometry or boundary, i need to consider the fixed 3-D Cartesian mesh which is generated from(0,0,0)

can you give your opinion for my question?

i found Pointref. and this is reference point of Cartesian mesh. thanks Alex

good you find that