In a planar L-drawing of a directed graph (digraph) each edge e is represented as a polyline composed of a vertical segment starting at the tail of e and a horizontal segment ending at the head of e. Distinct edges may overlap, but not cross. Our main focus is on bimodal graphs, i.e., digraphs admitting a planar embedding in which the incoming and outgoing edges around each vertex are contiguous. We show that every plane bimodal graph without 2-cycles admits a planar L-drawing. This includes the class of upward-plane graphs. Finally, outerplanar digraphs admit a planar L-drawing - although they do not always have a bimodal embedding - but not necessarily with an outerplanar embedding.

中文翻译：

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双峰图的平面 L 绘图

在有向图（有向图）的平面 L 图中，每条边 e 表示为由从 e 的尾部开始的垂直线段和在 e 的头部结束的水平线段组成的折线。不同的边缘可能会重叠，但不会交叉。我们的主要关注点是双峰图，即允许平面嵌入的有向图，其中每个顶点周围的传入和传出边是连续的。我们表明，每个没有 2 循环的平面双峰图都允许平面 L 绘图。这包括向上平面图类。最后，外平面有向图允许平面 L 绘图 - 尽管它们并不总是具有双峰嵌入 - 但不一定具有外平面嵌入。