manim - 如何确定多边形的边缘中心

Question

我使用多边形来制作三角形：

tri1 = Polygon(LEFT*1.5+UP, RIGHT*1.5+UP, RIGHT*1.5+UP*1.5)

然后我想在多边形的边缘中心显示三个文本。

c = TexMobject("c").next_to(tri1.get_edge_center(LEFT), UP)
a = TexMobject("a").next_to(tri1.get_edge_center(DOWN), DOWN)
b = TexMobject("b").next_to(tri1.get_edge_center(RIGHT), RIGHT)

但是“c”远离边缘中心，所以我改变了位置：

tri1.get_edge_center(LEFT)

至

interpolate(LEFT*1.5+UP, RIGHT*1.5+UP*1.5, 0.5)

看起来不错。但是我想使用一致的方式来做到这一点，如何使用 get_edge_center 获得“c”的位置？谢谢！

Answer 1

如果您检查 manimlib / mobject.py 库或 vector_mobject 库，您会发现没有类似的。让 manim 如此酷的一件事是，如果某事无法完成，您可以自己完成。我建议不要问，如果你没有找到方法，你自己创建它（就像插值一样）。通过这种方式，您将了解更多信息并开发自己的代码，而无需依赖于您能做什么或不能做什么。

class Polygon(Polygon):
    def get_center_of_edges(self,buff=SMALL_BUFF*3):
        vertices = self.get_vertices()
        coords_vertices = []
        for i in range(len(vertices)):
            if i < len(vertices)-1:
                p1,p2 = [vertices[i],vertices[i+1]]
            else:
                p1,p2 = [vertices[-1],vertices[0]]
            guide_line = Line(p1,p2)
            side = guide_line.get_center()
            normal_direction = guide_line.copy()
            normal_direction.rotate(-PI/2)
            vector_normal_direction = normal_direction.get_unit_vector()
            direction = Dot(side).shift(vector_normal_direction*buff).get_center()
            coords_vertices.append(direction)

        return coords_vertices


class PolygonScene(Scene):
    def construct(self):
        tri1 = Polygon(LEFT*1.5+UP, RIGHT*1.5+UP, RIGHT*1.5+UP*1.5)
        center_vertices =tri1.get_center_of_edges()
        labels = VGroup(*[
            TexMobject(label).move_to(point) for label,point in zip(["a","b","c"],center_vertices)
            ])

        self.add(tri1,labels)

class RegularPolygon(RegularPolygon):
    def get_center_of_edges(self,buff=SMALL_BUFF*3):
        vertices = self.get_vertices()
        coords_vertices = []
        for i in range(len(vertices)):
            if i < len(vertices)-1:
                p1,p2 = [vertices[i],vertices[i+1]]
            else:
                p1,p2 = [vertices[-1],vertices[0]]
            guide_line = Line(p1,p2)
            side = guide_line.get_center()
            normal_direction = guide_line.copy()
            normal_direction.rotate(-PI/2)
            vector_normal_direction = normal_direction.get_unit_vector()
            direction = Dot(side).shift(vector_normal_direction*buff).get_center()
            coords_vertices.append(direction)

        return coords_vertices


class PolygonScene2(Scene):
    def construct(self):
        tri1 = RegularPolygon(6).scale(2.5)
        center_vertices =tri1.get_center_of_edges()
        labels = ["a","b","c","d","e","f"]
        labels = VGroup(*[
            TexMobject(label).move_to(point) for label,point in zip(labels,center_vertices)
            ])

        self.add(tri1,labels)