Learning vtkjs之Calculator

news2024/9/22 5:27:15

过滤器公式计算器 Calculator

介绍

The Calculator filter is a fast way to add derived data arrays to a
dataset. These arrays can be defined over points, cells, or just field
data that is “uniform” across the dataset (i.e., constant over all of
space). Values in the array(s) you create are specified in terms of
existing arrays via a function you provide.

The Calculator filter is similar in spirit to VTK’s array calculator,
so it should be familiar to VTK users but the syntax takes advantage
of JavaScript’s flexibility.

chatGLM 翻译一下

计算器过滤器是一种快速向数据集中添加派生数据数组的方法。这些数组可以定义为点、单元格，或只是数据集中的“统一”场数据（即，在整个空间中是常数）。您创建的数组中的值是通过您提供的函数以现有数组为条件来指定的。

计算器过滤器在精神上类似于 VTK 的数组计算器，因此对 VTK 用户来说应该很熟悉，但其语法利用了 JavaScript 的灵活性。

用法

其实官方给的例子真的坑好多啊，比如interpolateScalarsBeforeMapping: false,才可以插值，useLookupTableScalarRange: false,才可以表示使用lookuptable，用起来很疑惑，你不看源码就不知道什么情况，它自己的例子也报错，运行不起来，最后需要自己debug一下
官方例子给的是setFormulaSimple方式，比较方便

核心代码

// 创建一个计算器的过滤器
const simpleFilter = vtkCalculator.newInstance();
    simpleFilter.setFormulaSimple(
      FieldDataTypes.POINT, // Generate an output array defined over points.
      [], // We don't request any point-data arrays because point coordinates are made available by default.
      "z", // Name the output array "z"
      (x) => (x[0] - 0.5) * (x[0] - 0.5) + (x[1] - 0.5) * (x[1] - 0.5) + 0.125
    ); // Our formula for z
// 利用的是scalar来修改变形
    const warpScalar = vtkWarpScalar.newInstance();
    const warpMapper = vtkMapper.newInstance({
      interpolateScalarsBeforeMapping: false,
      useLookupTableScalarRange: false,
      lookupTable,
    });
    const warpActor = vtkActor.newInstance();
    // warpActor.getProperty().setEdgeVisibility(true);

    // The generated 'z' array will become the default scalars, so the plane mapper will color by 'z':
    // 数据源是来自这个平面plane
    simpleFilter.setInputConnection(planeSource.getOutputPort());

    // We will also generate a surface whose points are displaced from the plane by 'z':
    warpScalar.setInputConnection(simpleFilter.getOutputPort());
    // 设置需要对应处理的数组的key
    warpScalar.setInputArrayToProcess(0, "z", "PointData", "Scalars");


    warpMapper.setInputConnection(warpScalar.getOutputPort());
    warpActor.setMapper(warpMapper);