Using ImmediateMesh

Unlike the SurfaceTool or ArrayMesh, ImmediateMesh is an actual node. Being a node makes it quick to add to a scene and get visual output. It uses an OpenGL 1.x-style API like SurfaceTool, but it's actually designed to create meshes on the fly.

Generating complex geometry (several thousand vertices) with this node is inefficient, even if it's done only once. Instead, it is designed to generate simple geometry that changes every frame.

Before starting, you should clear the geometry by calling clear_surfaces(). This ensures that you are not building upon the geometry from the previous frame. If you want to keep geometry between frames, do not call clear_surfaces().

To begin generating geometry you must call surface_begin(). surface_begin() takes a PrimitiveType as an argument. PrimitiveType is an OpenGL concept that instructs the GPU how to arrange the primitive based on the vertices given whether it is triangles, lines, points, etc. A complete list can be found under the Mesh class reference page.

Once you have called surface_begin() you are ready to start adding vertices. You add vertices one at a time. First you add vertex specific attributes such as normals or UVs using surface_set_****() (e.g. surface_set_normal()). Then you call surface_add_vertex() to add a vertex with those attributes. For example:

GDScript

# Add a vertex with normal and uv.
surface_set_normal(Vector3(0, 1, 0))
surface_set_uv(Vector2(1, 1))
surface_add_vertex(Vector3(0, 0, 1))

Only attributes added before the call to surface_add_vertex() will be included in that vertex.

Finally, once you have added all your vertices call surface_end() to signal that you have finished generating the mesh.

The example code below draws a single triangle.

GDScript

extends ImmediateMesh

func _process(_delta):
    # Clean up before drawing.
    clear_surfaces()

    # Begin draw.
    surface_begin(Mesh.PRIMITIVE_TRIANGLES)

    # Prepare attributes for surface_add_vertex.
    surface_set_normal(Vector3(0, 0, 1))
    surface_set_uv(Vector2(0, 0))
    # Call last for each vertex, adds the above attributes.
    surface_add_vertex(Vector3(-1, -1, 0))

    surface_set_normal(Vector3(0, 0, 1))
    surface_set_uv(Vector2(0, 1))
    surface_add_vertex(Vector3(-1, 1, 0))

    surface_set_normal(Vector3(0, 0, 1))
    surface_set_uv(Vector2(1, 1))
    surface_add_vertex(Vector3(1, 1, 0))

    # End drawing.
    surface_end()