Add isNaN, isFinite, null, and undefined support to GLSL styling backend

CHANGES.md

@@ -9,6 +9,7 @@ Change Log
 * Added `tileset.uri`, `tileset.show`, and `tileset.maximumScreenSpaceError` properties to CZML processing for loading 3D Tiles.
 * Added `Color.lerp` for linearly interpolating between two RGB colors. [#8607](https:/CesiumGS/cesium/pull/8607)
 * `CesiumTerrainProvider` now supports terrain tiles using a `WebMercatorTilingScheme` by specifying `"projection": "EPSG:3857"` in `layer.json`. It also now supports numbering tiles from the North instead of the South by specifying `"scheme": "slippyMap"` in `layer.json`. [#8563](https:/CesiumGS/cesium/pull/8563)
+* Added basic support for `isNaN`, `isFinite`, `null`, and `undefined` in the 3D Tiles styling GLSL backend for point clouds. [#8621](https:/CesiumGS/cesium/pull/8621)
 
 ##### Fixes :wrench:
 

Source/Scene/Expression.js

@@ -1559,6 +1559,8 @@ import ExpressionNodeType from './ExpressionNodeType.js';
  return expressions;
  }
 
+ var nullSentinel = 'czm_infinity'; // null just needs to be some sentinel value that will cause "[expression] === null" to be false in nearly all cases. GLSL doesn't have a NaN constant so use czm_infinity.
+
  Node.prototype.getShaderExpression = function(attributePrefix, shaderState, parent) {
  var color;
  var left;
@@ -1603,7 +1605,13 @@ import ExpressionNodeType from './ExpressionNodeType.js';
  return 'floor(' + left + ' + 0.5)';
  } else if (defined(unaryFunctions[value])) {
  return value + '(' + left + ')';
- } else if ((value === 'isNaN') || (value === 'isFinite') || (value === 'String') || (value === 'isExactClass') || (value === 'isClass') || (value === 'getExactClassName')) {
+ } else if (value === 'isNaN') {
+ // In GLSL 2.0 use isnan instead
+ return '(' + left + ' != ' + left + ')';
+ } else if (value === 'isFinite') {
+ // In GLSL 2.0 use isinf instead. GLSL doesn't have an infinity constant so use czm_infinity which is an arbitrarily big enough number.
+ return '(abs(' + left + ') < czm_infinity)';
+ } else if ((value === 'String') || (value === 'isExactClass') || (value === 'isClass') || (value === 'getExactClassName')) {
  throw new RuntimeError('Error generating style shader: "' + value + '" is not supported.');
  } else if (defined(unaryFunctions[value])) {
  return value + '(' + left + ')';
@@ -1659,7 +1667,7 @@ import ExpressionNodeType from './ExpressionNodeType.js';
  case ExpressionNodeType.VARIABLE_IN_STRING:
  throw new RuntimeError('Error generating style shader: Converting a variable to a string is not supported.');
  case ExpressionNodeType.LITERAL_NULL:
- throw new RuntimeError('Error generating style shader: null is not supported.');
+ return nullSentinel;
  case ExpressionNodeType.LITERAL_BOOLEAN:
  return value ? 'true' : 'false';
  case ExpressionNodeType.LITERAL_NUMBER:
@@ -1745,7 +1753,7 @@ import ExpressionNodeType from './ExpressionNodeType.js';
  case ExpressionNodeType.LITERAL_REGEX:
  throw new RuntimeError('Error generating style shader: Regular expressions are not supported.');
  case ExpressionNodeType.LITERAL_UNDEFINED:
- throw new RuntimeError('Error generating style shader: undefined is not supported.');
+ return nullSentinel;
  case ExpressionNodeType.BUILTIN_VARIABLE:
  if (value === 'tiles3d_tileset_time') {
  return 'u_time';

Specs/Scene/ExpressionSpec.js

@@ -3546,6 +3546,34 @@ describe('Scene/Expression', function() {
  expect(shaderExpression).toEqual(expected);
  });
 
+ it('gets shader expression for isNaN', function() {
+ var expression = new Expression('isNaN(1.0)');
+ var shaderExpression = expression.getShaderExpression('', {});
+ var expected = '(1.0 != 1.0)';
+ expect(shaderExpression).toEqual(expected);
+ });
+
+ it('gets shader expression for isFinite', function() {
+ var expression = new Expression('isFinite(1.0)');
+ var shaderExpression = expression.getShaderExpression('', {});
+ var expected = '(abs(1.0) < czm_infinity)';
+ expect(shaderExpression).toEqual(expected);
+ });
+
+ it('gets shader expression for null', function() {
+ var expression = new Expression('null');
+ var shaderExpression = expression.getShaderExpression('', {});
+ var expected = 'czm_infinity';
+ expect(shaderExpression).toEqual(expected);
+ });
+
+ it('gets shader expression for undefined', function() {
+ var expression = new Expression('undefined');
+ var shaderExpression = expression.getShaderExpression('', {});
+ var expected = 'czm_infinity';
+ expect(shaderExpression).toEqual(expected);
+ });
+
  it('throws when getting shader expression for regex', function() {
  var expression = new Expression('regExp("a").test("abc")');
  expect(function() {
@@ -3610,34 +3638,6 @@ describe('Scene/Expression', function() {
  }).toThrowRuntimeError();
  });
 
- it('throws when getting shader expression for literal undefined', function() {
- var expression = new Expression('undefined');
- expect(function() {
- return expression.getShaderExpression('', {});
- }).toThrowRuntimeError();
- });
-
- it('throws when getting shader expression for literal null', function() {
- var expression = new Expression('null');
- expect(function() {
- return expression.getShaderExpression('', {});
- }).toThrowRuntimeError();
- });
-
- it('throws when getting shader expression for isNaN', function() {
- var expression = new Expression('isNaN(1.0)');
- expect(function() {
- return expression.getShaderExpression('', {});
- }).toThrowRuntimeError();
- });
-
- it('throws when getting shader expression for isFinite', function() {
- var expression = new Expression('isFinite(1.0)');
- expect(function() {
- return expression.getShaderExpression('', {});
- }).toThrowRuntimeError();
- });
-
  it('throws when getting shader expression for isExactClass', function() {
  var expression = new Expression('isExactClass("door")');
  expect(function() {