python - 检查顶点在相机 View 中是否可见并渲染或被遮挡

Question

我正在处理机器学习任务，我正在尝试使用 Blender 生成合成图像作为神经网络的训练数据集。为此，我必须在渲染图像中找到对象的边界框。

到目前为止，我的代码很大程度上基于建议的 in this thread ，但这并不关心顶点是否可见或被另一个对象遮挡。想要的结果确实和解释的完全一样here .我已经尝试了那里给出的建议，但它不起作用。我不明白是因为我给 ray_cast 函数提供了错误的输入(因为 bpy API 真的很糟糕)，还是仅仅因为函数的性能很差，正如我在其他地方读到的那样。我的代码，现在，是:

import bpy
import numpy as np

def boundingbox(scene, camera, obj, limit = 0.3):
    #  Get the inverse transformation matrix.
    matrix = camera.matrix_world.normalized().inverted()
    #  Create a new mesh data block, using the inverse transform matrix to undo any transformations.
    dg = bpy.context.evaluated_depsgraph_get()
    #    eval_obj = bpy.context.object.evaluated_get(dg)
    eval_obj = obj.evaluated_get(dg)
    mesh = eval_obj.to_mesh()
    mesh.transform(obj.matrix_world)
    mesh.transform(matrix)

    #  Get the world coordinates for the camera frame bounding box, before any transformations.
    frame = [-v for v in camera.data.view_frame(scene=scene)[:3]]
    origin = camera.location
    lx = []
    ly = []

    for v in mesh.vertices:
        co_local = v.co
        z = -co_local.z
        direction =  (co_local - origin)


        result = scene.ray_cast(view_layer=bpy.context.window.view_layer, origin=origin,
                                      direction= direction) # interested only in the first return value
        intersection = result[0]
        met_obj = result[4]
        if intersection:
            if met_obj.type == 'CAMERA':
                intersection = False


        if z <= 0.0 or (intersection == True and (result[1] - co_local).length > limit):
            #  Vertex is behind the camera or another object; ignore it.
            continue
        else:
            # Perspective division
            frame = [(v / (v.z / z)) for v in frame]

        min_x, max_x = frame[1].x, frame[2].x
        min_y, max_y = frame[0].y, frame[1].y

        x = (co_local.x - min_x) / (max_x - min_x)
        y = (co_local.y - min_y) / (max_y - min_y)

        lx.append(x)
        ly.append(y)

    eval_obj.to_mesh_clear()

    #  Image is not in view if all the mesh verts were ignored
    if not lx or not ly:
        return None

    min_x = np.clip(min(lx), 0.0, 1.0)
    min_y = np.clip(min(ly), 0.0, 1.0)
    max_x = np.clip(max(lx), 0.0, 1.0)
    max_y = np.clip(max(ly), 0.0, 1.0)

    #  Image is not in view if both bounding points exist on the same side
    if min_x == max_x or min_y == max_y:
        return None

    # Figure out the rendered image size
    render = scene.render
    fac = render.resolution_percentage * 0.01
    dim_x = render.resolution_x * fac
    dim_y = render.resolution_y * fac

    # return box in the form (top left x, top left y),(width, height)
    return (
        (round(min_x * dim_x),  # X
         round(dim_y - max_y * dim_y)),  # Y
        (round((max_x - min_x) * dim_x),  # Width
         round((max_y - min_y) * dim_y))  # Height
    )

我还尝试将光线从顶点转换到相机位置(而不是相反)并使用小立方体解决方法，如 here 所述。 ，但无济于事。请有人帮我弄清楚如何正确地做到这一点或提出另一种策略吗？

Answer 1

我必须解决一个非常相似的问题
这是我使用的代码

def BoundingBoxFinal(obj,cam):
from bpy_extras.object_utils import world_to_camera_view
scene = bpy.context.scene
# needed to rescale 2d coordinates
render = scene.render
render_scale = scene.render.resolution_percentage / 100
res_x = render.resolution_x *render_scale
res_y = render.resolution_y *render_scale
# use generator expressions () or list comprehensions []
mat = obj.matrix_world
verts = [vert.co for vert in obj.data.vertices]
for i in range(len(verts)):
    verts[i] = obj.matrix_world @ verts[i]


coords_2d = [world_to_camera_view(scene, cam, coord) for coord in verts]

# 2d data printout:
rnd = lambda i: round(i)


X_max = max(coords_2d[0])
Y_max = max(coords_2d[1])
X_min = min(coords_2d[0])
Y_min = min(coords_2d[1])

verts_2d =[]
for x, y, distance_to_lens in coords_2d:
    verts_2d.append(tuple((rnd(res_x*x), rnd(res_y-res_y*y))))

Y_max = max(verts_2d, key = lambda i : i[1])[1]
X_max = max(verts_2d, key = lambda i : i[0])[0]
Y_min = min(verts_2d, key = lambda i : i[1])[1]
X_min = min(verts_2d, key = lambda i : i[0])[0]

verts_2d.clear()

return(
    X_min,
    Y_min,
    X_max,
    Y_max,
    obj.data.name.split('.')[0]
)