软件工程应用与实践（2）可视化-自定义可视化

 2021SC@SDUSC

open3d

通过draw_geometries()和draw_geometries_with_custom_animation()函数可以很方便的使用Open3d的可视化功能，所有的都可以通过GUI去完成。

import open3d as o3d


def custom_draw_geometry(pcd):
    # The following code achieves the same effect as:
    # o3d.visualization.draw_geometries([pcd])
    vis = o3d.visualization.Visualizer()
    vis.create_window()
    vis.add_geometry(pcd)
    vis.run()
    vis.destroy_window()


pcd = o3d.io.read_point_cloud("fragment.ply")

print("Customized visualization to mimic DrawGeometry")
custom_draw_geometry(pcd)

 通过Visualizer类模仿draw_geometries()功能，产生的功能与draw_geometries()完全相同。 用来实现对几何对象的渲染可视化。在可视化界面能够通过鼠标进行缩放，旋转和平移，改变渲染风格和屏幕截图等。

import open3d as o3d


def custom_draw_geometry_load_option(pcd):
    vis = o3d.visualization.Visualizer()
    vis.create_window()
    vis.add_geometry(pcd)
    vis.get_render_option().load_from_json("renderoption.json")
    vis.run()
    vis.destroy_window()


pcd = o3d.io.read_point_cloud("fragment.ply")

print("Customized visualization showing normal rendering")
custom_draw_geometry_load_option(pcd)

以上函数读取储存在json文件中预定义的RenderOption。Visualizer类中还有其他一些变量比如viewControl等。

def custom_draw_geometry_with_rotation(pcd):

    def rotate_view(vis):
        ctr = vis.get_view_control()
        ctr.rotate(10.0, 0.0)
        return False

    o3d.visualization.draw_geometries_with_animation_callback([pcd],
                                                              rotate_view)

  draw_geometries_with_animation_callback注册一个Python回调函数notate_view作为主循环的空闲函数。当可视化器空闲时，它沿着x轴旋转视图。其控制了一个旋转的动画行为，展示给人的效果是三百六十度无死角旋转以达到好的用户体验。

import open3d as o3d
import numpy as np
import matplotlib.pyplot as plt


def custom_draw_geometry_with_key_callback(pcd):

    def change_background_to_black(vis):
        opt = vis.get_render_option()
        opt.background_color = np.asarray([0, 0, 0])
        return False

    def load_render_option(vis):
        vis.get_render_option().load_from_json(
            "renderoption.json")
        return False

    def capture_depth(vis):
        depth = vis.capture_depth_float_buffer()
        plt.imshow(np.asarray(depth))
        plt.show()
        return False

    def capture_image(vis):
        image = vis.capture_screen_float_buffer()
        plt.imshow(np.asarray(image))
        plt.show()
        return False

    key_to_callback = {}
    key_to_callback[ord("K")] = change_background_to_black
    key_to_callback[ord("R")] = load_render_option
    key_to_callback[ord(",")] = capture_depth
    key_to_callback[ord(".")] = capture_image
    o3d.visualization.draw_geometries_with_key_callbacks([pcd], key_to_callback)


pcd = o3d.io.read_point_cloud("侍女1.pcd")

print("Customized visualization with key press callbacks")
print("   Press 'K' to change background color to black")
print("   Press 'R' to load a customized render option, showing normals")
print("   Press ',' to capture the depth buffer and show it")
print("   Press '.' to capture the screen and show it")
custom_draw_geometry_with_key_callback(pcd)

 当给程序一个按键时，也可以生成回调函数。上面的函数就注册了几个按键。比如按k将背景颜色更改为黑色。

控制改变视角

import open3d as o3d


def custom_draw_geometry_with_custom_fov(pcd, fov_step):
    vis = o3d.visualization.Visualizer()
    vis.create_window()
    vis.add_geometry(pcd)
    ctr = vis.get_view_control()
    print("Field of view (before changing) %.2f" % ctr.get_field_of_view())
    ctr.change_field_of_view(step=fov_step)  # 改变视角
    print("Field of view (after changing) %.2f" % ctr.get_field_of_view())
    vis.run()
    vis.destroy_window()


pcd = o3d.io.read_point_cloud("fragment.ply")

print("Changing field of view")
custom_draw_geometry_with_custom_fov(pcd, 90.0)
custom_draw_geometry_with_custom_fov(pcd, -90.0)

要去改变我们观看的视角，必须先获取可视化控件的实例。使用change_field_of_view 函数改变视角。 

 视场(FoV)可以在范围[5,90]内设置一个度。注意函数change_field_of_view()将指定的FoV添加到当前FoV中。默认情况下，可视化器的视场为60度。调用以下代码:

custom_draw_geometry_with_custom_fov(pcd, 90.0)
custom_draw_geometry_with_custom_fov(pcd, -10.0)

FoV默认最大为60度， 当设置超过最大的FoV时，FoV将被设置为90度；设置的FoV低于最小的FoV时，FoV将被设置为5度。

捕获图像相关操作

import os
import open3d as o3d
import numpy as np
import matplotlib.pyplot as plt


def custom_draw_geometry_with_camera_trajectory(pcd):
    custom_draw_geometry_with_camera_trajectory.index = -1
    custom_draw_geometry_with_camera_trajectory.trajectory =\
            o3d.io.read_pinhole_camera_trajectory(
                    "../../test_data/camera_trajectory.json")
    custom_draw_geometry_with_camera_trajectory.vis = o3d.visualization.Visualizer(
    )
    if not os.path.exists("../../test_data/image/"):
        os.makedirs("../../test_data/image/")
    if not os.path.exists("../../test_data/depth/"):
        os.makedirs("../../test_data/depth/")

    def move_forward(vis):
        # This function is called within the o3d.visualization.Visualizer::run() loop
        # The run loop calls the function, then re-render
        # So the sequence in this function is to:
        # 1. Capture frame
        # 2. index++, check ending criteria
        # 3. Set camera
        # 4. (Re-render)
        ctr = vis.get_view_control()
        glb = custom_draw_geometry_with_camera_trajectory
        if glb.index >= 0:
            print("Capture image {:05d}".format(glb.index))
            depth = vis.capture_depth_float_buffer(False)
            image = vis.capture_screen_float_buffer(False)
            plt.imsave("../../test_data/depth/{:05d}.png".format(glb.index),\
                    np.asarray(depth), dpi = 1)
            plt.imsave("../../test_data/image/{:05d}.png".format(glb.index),\
                    np.asarray(image), dpi = 1)
            # vis.capture_depth_image("depth/{:05d}.png".format(glb.index), False)
            # vis.capture_screen_image("image/{:05d}.png".format(glb.index), False)
        glb.index = glb.index + 1
        if glb.index < len(glb.trajectory.parameters):
            ctr.convert_from_pinhole_camera_parameters(
                glb.trajectory.parameters[glb.index])
        else:
            custom_draw_geometry_with_camera_trajectory.vis.\
                    register_animation_callback(None)
        return False

    vis = custom_draw_geometry_with_camera_trajectory.vis
    vis.create_window()
    vis.add_geometry(pcd)
    vis.get_render_option().load_from_json("renderoption.json")
    vis.register_animation_callback(move_forward)
    vis.run()
    vis.destroy_window()


pcd = o3d.io.read_point_cloud("fragment.ply")

print("6. Customized visualization playing a camera trajectory")
custom_draw_geometry_with_camera_trajectory(pcd)

这个函数读取了相机轨迹，然后自定义了动画函数move_forward 以遍历相机轨迹。在这个函数中，彩色图像和深度图像分别使用visualizer.capture_depth_float_buffer和Visualizer.capture_screen_float_buffer去捕获，然后保存成文件。