.. _stdlib_custom_mesh:

=======================
Create Your Custom Mesh
=======================

Occasionally, you may want to create your own mesh. In this example, we will create a simple mesh with a single quad. Let's first show the code and then explain it::

    require engine.gen_geometry.mesh_structures

    def create_quad_mesh() : MeshId {
        var vertices = [float3(0, 0, 0), float3(0, 1, 0), float3(1, 1, 0), float3(1, 0, 0)]
        var normals = [float3(0, 0, -1), float3(0, 0, -1), float3(0, 0, -1), float3(0, 0, -1)]
        var uvs = [float2(0, 0), float2(0, 1), float2(1, 1), float2(1, 0)]

        // two-sided quad
        var triangles = [uint3(0u, 1u, 2u), uint3(2u, 3u, 0u), uint3(0u, 2u, 1u), uint3(2u, 0u, 3u)]

        return create_mesh(MeshGeometry(vertices <- vertices, normals <- normals, uv <- uvs, triangles <- triangles))
    }


First, we require the module that contains all the types and functions we need. Then, we define a function that generates a quad mesh. Inside the function, we define the vertices and triangles of the quad. It's a two-sided quad, so you can use only half of the triangles if you want a single-sided quad. The vertices are defined as an array of `Vertex` objects, where each `Vertex` object contains the position, normal, and texture coordinate of a vertex. The triangles are defined as an array of `uint3` objects, where each `uint3` object contains the indices of the vertices that form a triangle. In any mesh you create, you need to define the vertices and indices that make up the mesh. Finally, we create a `MeshData` object with the generated vertices and indices and pass it to the `create_mesh` function.


Now let's show how to generate this mesh in your game script::

    let mesh = create_quad_mesh()
    let node = create_node()
    add_component(node, new Mesh(meshId = mesh))