使用PDG制作城市FOUNDATIONS | BUILD A CITY WITH PDG

Houdini Foundations – PDG _ Introduction

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
A quick overview of all the different parts of the lesson. Take a look at where you are headed with this lesson.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
快速概览课程的所有不同部分。看一下本课的学习方向。

Houdini Foundations – PDG 1 _ Create a City Grid

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
To build a procedural city, you will start with a city grid. You are going to create the geometry by tracing an image file that includes a black and white image of a city map. This will be the input geometry for the network you will be building in TOPs.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
要构建程序化城市，您将从城市网格开始。您将通过追踪包含城市地图黑白图像的图像文件来创建几何图形。这将是您将在 TOP 中构建的网络的输入几何。

Houdini Foundations – PDG 2 _ Generate and Display Work Items

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
Now that you have a city grid, you can break out the different city blocks into separate work items. That will allow you to use each block to generate buildings. You will set up a TOP network to save out each of the blocks. At the same time, you will create an object for visualizing selected work items to verify that you are getting the results you want.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
现在您有了城市网格，您可以将不同的城市街区分解为单独的工作项目。这将允许您使用每个块来生成建筑物。您将设置一个 TOP 网络来保存每个块。同时，您将创建一个对象来可视化选定的工作项，以验证您是否获得了想要的结果。

Houdini Foundations – PDG 3 _ Add Attributes

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
To create buildings, you want to set a fixed base height and a random height variation so that your buildings are not all the same size. You could set up these attributes at the geometry level of the city map but you can also assign them here in TOPs. This will make it easier to make changes at the TOP level if needed down the line.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
要创建建筑物，您需要设置固定的基础高度和随机的高度变化，以便您的建筑物大小不尽相同。您可以在城市地图的几何级别设置这些属性，但您也可以在 TOP 中分配它们。如果需要，这将使在 TOP 级别进行更改变得更加容易。

Houdini Foundations – PDG 4 _ Create Buildings for the City Grid

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
You are now going to use a ROP Geometry node to create a simple building. To see what you are doing in the viewport, you need to generate the work items and select one of them. You can then use that work item to design the building at the geometry level.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
您现在将使用 ROP Geometry 节点创建一个简单的建筑物。要在视口中查看您在做什么，您需要生成工作项并选择其中之一。然后，您可以使用该工作项在几何级别设计建筑物。

Houdini Foundations – PDG 5 _ Combine the Buildings

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
Once the buildings have been completed, you will want to bring them back together to create the city. This involves a partition node called Wait for All and a Geometry Import. You will also add in a city core where the buildings will be taller than elsewhere in the city.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
建筑物完工后，您将希望将它们重新组合在一起以创建城市。这涉及一个名为 Wait for All 的分区节点和一个 Geometry Import。您还将添加一个城市核心，其中的建筑物将高于城市的其他地方。

Houdini Foundations – PDG 6 _ Isolate a Building

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
Up until now the building heights are determined by the randomness of the height_variation. If there is one building that you want to fix to a certain height, a second attribute create node can be used to choose a primitive and set specific values. This makes it easier to art direct a system when you want to override the randomness.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
到目前为止，建筑物的高度是由 height_variation 的随机性决定的。如果您想将一栋建筑物固定到特定高度，则可以使用第二个属性创建节点来选择基元并设置特定值。当您想要覆盖随机性时，这使得艺术指导系统变得更容易。

Houdini Foundations – PDG 7 _ Wedge the City Core Location

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
In order to wedge the position of the sphere within the street_grid object, the network will need to be turned into a Houdini Digital Asset [HDA] and run through an HDA Processor TOP node. The ability to load these assets and add them to the system lets you create a complex system out of discreet tools that can be updated and adapted as needed.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
为了将球体的位置楔入 street_grid 对象中，需要将网络转换为 Houdini 数字资产 [HDA] 并通过 HDA 处理器 TOP 节点运行。加载这些资产并将它们添加到系统的能力使您可以使用谨慎的工具创建一个复杂的系统，这些工具可以根据需要进行更新和调整。

Houdini Foundations – PDG 8 _ Create Geometry for the Streets

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
To create context for the buildings, you will now create city blocks and streets to use in the final rendering. While the four wedges currently all use the same map, you will set up this geometry in TOPs to allow for the use of different maps down the line. It is always a good idea to build in flexibility to create the most robust system.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
要为建筑物创建上下文，您现在将创建城市街区和街道以用于最终渲染。虽然四个楔形目前都使用相同的贴图，但您将在 TOP 中设置此几何图形以允许使用不同的贴图。构建灵活性以创建最强大的系统始终是一个好主意。

Houdini Foundations – PDG 9 _ Wedge Four City Maps

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
Let’s add one extra variable into the wedging. You are going to access four different maps and create one rendering for each one of them. Each of the different black and while images will be traced and used to feed the system. This shows another way to add more content into the pipeline.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
让我们在楔形中添加一个额外的变量。您将访问四张不同的地图并为每张地图创建一个渲染图。每个不同的黑色和白色图像都将被跟踪并用于提供给系统。这显示了另一种将更多内容添加到管道中的方法。

Houdini Foundations – PDG 10 _ Render a Mosaic

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
Now you are going to add a camera and a skylight then render out the cities. The resulting images will then be combined into a single mosaic with the wedge attributes on display so that creative decisions can be made based on the results. The mosaic node will use the Image Magick application which needs to be installed on your computer for these steps to work.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
现在您要添加摄像机和天窗，然后渲染城市。然后，生成的图像将组合成单个马赛克，并显示楔形属性，以便可以根据结果做出创意决策。马赛克节点将使用 Image Magick 应用程序，该应用程序需要安装在您的计算机上才能使这些步骤生效。

Houdini Foundations – PDG 11 _ Scale Up to Create More Content

Lessons and Project Files: sidefx.com/tutorials/foundations-build-a-city-with-pdg/
In the beginning you pointed out that this city building example could probably be created in SOPs without too much difficulty. The issue is that as the system gets more complex there is a bottleneck since all the processing happens within a single network. With TOPs, you can distribute work items to a compute farm and as you scale up things don’t have to slow down.
谷歌翻译：
课程和项目文件：sidefx.com/tutorials/foundations-build-a-city-with-pdg/
一开始您指出，这个城市建筑示例可能可以在 SOP 中创建而不会有太多困难。问题在于，随着系统变得越来越复杂，会出现瓶颈，因为所有处理都发生在单个网络中。使用 TOP，您可以将工作项分发到计算场，并且在扩展时不必放慢速度。