Using ImmediateGeometry

Unlike the SurfaceTool or ArrayMesh, ImmediateGeometry is an actual node. Being an node makes it quick to add to a scene and get visual output. It uses an “OpenGL 1.x” style API like the SurfaceTool, but it’s actually designed to create content 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 clear the geometry by calling clear(). 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().

To begin generating geometry you must call begin(). 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 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 set_****() (e.g. set_normal()). Then you call add_vertex() to add a vertex with those attributes. For example:

# Add a vertex with normal and uv
set_normal(Vector3(0, 1, 0))
set_uv(Vector2(1, 1))
add_vertex(Vector3(0, 0, 1))

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

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

The example code below draws a single triangle.

extends ImmediateGeometry

func _process(delta):
    # Clean up before drawing.
    clear()

    # Begin draw.
    begin(Mesh.PRIMITIVE_TRIANGLES)

    # Prepare attributes for add_vertex.
    set_normal( Vector3(0, 0, 1))
    set_uv(Vector2(0, 0))
    # Call last for each vertex, adds the above attributes.
    add_vertex(Vector3(-1, -1, 0))

    set_normal(Vector3(0, 0, 1))
    set_uv(Vector2(0, 1))
    add_vertex(Vector3(-1, 1, 0))

    set_normal(Vector3(0, 0, 1))
    set_uv(Vector2(1, 1))
    add_vertex(Vector3(1, 1, 0))

    # End drawing.
    end()