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Version: v1.0.3

A New UI system: GGUI

OSWindows / Linux / Mac OS X
Backendx64 / CUDA / Vulkan

Starting from v0.8.0, Taichi adds a new UI system GGUI. The new system uses GPU for rendering, making it much faster to render 3D scenes. That is why this new system gets its name as GGUI. This document describes the APIs that it provides.


If you choose Vulkan as backend, ensure that you install the Vulkan environment.


It is recommended that you familiarize yourself with GGUI through the examples in examples/ggui_examples.

Create a window​

ti.ui.Window(name, res) creates a window.

window = ti.ui.Window('Window Title', (640, 360))

The following three types of objects can be displayed on a ti.ui.Window:

  • 2D Canvas, which can be used to draw simple 2D geometries such as circles and triangles.
  • 3D Scene, which can be used to render 3D meshes and particles, with a configurable camera and light sources.
  • Immediate mode GUI components, for example buttons and textboxes.

2D Canvas​

Create a canvas​

The following code retrieves a Canvas object that covers the entire window.

canvas = window.get_canvas()

Draw on the canvas​

canvas.triangles(vertices, color, indices, per_vertex_color)
canvas.circles(vertices, radius, color, per_vertex_color)
canvas.lines(vertices, width, indices, color, per_vertex_color)

The arguments vertices, indices, per_vertex_color, and image must be Taichi fields. If per_vertex_color is provided, color is ignored.

The positions/centers of geometries are represented as floats between 0.0 and 1.0, which indicate the relative positions of the geometries on the canvas. For circles() and lines(), the radius and width arguments are relative to the height of the window.

The canvas is cleared after every frame. Always call these methods within the render loop.

3D Scene​

Create a scene​

scene = ti.ui.Scene()

Configure camera​

camera = ti.ui.make_camera()

Configuring light sources​

Add a point light​

Call point_light() to add a point light to the scene.

scene.point_light(pos, color)

Note that you need to call point_light() for every frame. Similar to the canvas() methods, call this method within your render loop.

3D Geometries​

scene.mesh(vertices, indices, normals, color, per_vertex_color)
scene.particles(vertices, radius, color, per_vertex_color)

The arguments vertices, indices, per_vertex_color, and image are all expected to be Taichi fields. If per_vertex_color is provided, color is ignored.

The positions/centers of geometries should be in the world-space coordinates.


If a mesh has num triangles, the indices should be a 1D scalar field with a shape (num * 3), not a vector field.

normals is an optional parameter for scene.mesh().

Rendering the scene​

You can render a scene on a canvas.


GUI components​

The design of GGUI's GUI components follows the Dear ImGui APIs.

window.GUI.begin(name, x, y, width, height)
is_clicked = window.GUI.button(name)
new_value = window.GUI.slider_float(name, old_value, min_value, max_value)
new_color = window.GUI.color_edit_3(name, old_color)

Show a window​

Call show() to show a window.


Call this method only at the end of the render loop for each frame.

User input processing​

To retrieve the events that have occurred since the last method call:

events = window.get_events()

Each event in events is an instance of ti.ui.Event. It has the following properties:

  • event.action, which can be ti.ui.PRESS, ti.ui.RELEASE, or ti.ui.MOTION.
  • event.key: the key related to this event.

To retrieve the mouse position:

  • window.get_cursor_pos()

To check if a key is pressed:

  • window.is_pressed(key)

The following is a user input processing example from mpm128:

while window.running:
# keyboard event processing
if window.get_event(ti.ui.PRESS):
if window.event.key == 'r': reset()
elif window.event.key in [ti.ui.ESCAPE]: break
if window.event is not None: gravity[None] = [0, 0] # if had any event
if window.is_pressed(ti.ui.LEFT, 'a'): gravity[None][0] = -1
if window.is_pressed(ti.ui.RIGHT, 'd'): gravity[None][0] = 1
if window.is_pressed(ti.ui.UP, 'w'): gravity[None][1] = 1
if window.is_pressed(ti.ui.DOWN, 's'): gravity[None][1] = -1

# mouse event processing
mouse = window.get_cursor_pos()
# ...
if window.is_pressed(ti.ui.LMB):
attractor_strength[None] = 1
if window.is_pressed(ti.ui.RMB):
attractor_strength[None] = -1

Image I/O​

To write the current frame in the window to an image file:


Note that you must call window.write_image() before calling

Off-screen rendering​

GGUI supports saving frames to images without showing the window. This is also known as "headless" rendering. To enable this mode, set the argument show_window to False when initializing a window.

window = ti.ui.Window('Window Title', (640, 360), show_window = False)

Then you can call window.write_image() as normal and remove the call at the end.