improve attribute reliability for ground primitive materials

CHANGES.md

@@ -26,6 +26,7 @@ Change Log
 * Fixed labels not showing for individual entities in data sources when clustering is enabled. [#6087](https://github.com/AnalyticalGraphicsInc/cesium/issues/6087)
 * Fixed a crash for 3D Tiles that have zero volume. [#7945](https://github.com/AnalyticalGraphicsInc/cesium/pull/7945)
 * Fixed a bug where dynamic polylines did not use the given arcType. [#8191](https://github.com/AnalyticalGraphicsInc/cesium/issues/8191)
+* Fixed an issue where polygons, corridors, rectangles, and ellipses on terrain would not render on some mobile devices. [#6739](https://github.com/AnalyticalGraphicsInc/cesium/issues/6739)
 * Fixed a bug where GlobeSurfaceTile would not render the tile until all layers completed loading causing globe to appear to hang. [#7974](https://github.com/AnalyticalGraphicsInc/cesium/issues/7974)
 
 ### 1.61 - 2019-09-03

Source/Renderer/ComputeCommand.js

@@ -107,7 +107,7 @@ define([
     /**
      * Executes the compute command.
      *
-     * @param {Context} computeEngine The context that processes the compute command.
+     * @param {ComputeEngine} computeEngine The context that processes the compute command.
      */
     ComputeCommand.prototype.execute = function(computeEngine) {
         computeEngine.execute(this);

Source/Renderer/Context.js

@@ -18,6 +18,7 @@ define([
         '../Core/WebGLConstants',
         '../Shaders/ViewportQuadVS',
         './BufferUsage',
+        './checkFloatTexturePrecision',
         './ClearCommand',
         './ContextLimits',
         './CubeMap',
@@ -51,6 +52,7 @@ define([
         WebGLConstants,
         ViewportQuadVS,
         BufferUsage,
+        checkFloatTexturePrecision,
         ClearCommand,
         ContextLimits,
         CubeMap,
@@ -445,6 +447,8 @@ define([
         this.cache = {};
 
         RenderState.apply(gl, rs, ps);
+
+        this._floatTexSixPlaces = checkFloatTexturePrecision(this);
     }
 
     var defaultFramebufferMarker = {};
@@ -586,6 +590,18 @@ define([
             }
         },
 
+        /**
+         * <code>true</code> returns if the context's floating point textures support 6 decimal places of precision.
+         * @memberof Context.prototype
+         * @type {Boolean}
+         * @see {@link https://www.khronos.org/registry/webgl/extensions/OES_texture_float/}
+         */
+        floatTextureSixPlaces : {
+            get : function() {
+                return this._floatTexSixPlaces;
+            }
+        },
+
         /**
          * <code>true</code> if OES_texture_half_float is supported. This extension provides
          * access to floating point textures that, for example, can be attached to framebuffers for high dynamic range.

Source/Renderer/checkFloatTexturePrecision.js

@@ -0,0 +1,101 @@
+define([
+    '../Core/PixelFormat',
+    '../Shaders/CheckFloatTexturePrecisionFS',
+    './ComputeCommand',
+    './ComputeEngine',
+    './Framebuffer',
+    './PixelDatatype',
+    './Texture'
+], function(
+    PixelFormat,
+    CheckFloatTexturePrecisionFS,
+    ComputeCommand,
+    ComputeEngine,
+    Framebuffer,
+    PixelDatatype,
+    Texture
+) {
+    'use strict';
+
+    /**
+     * Checks if the context's floating point textures support 6 decimal places of precision.
+     *
+     * @param {Context} context A context wrapping a gl implementation.
+     * @returns {Boolean} whether or not the context's floating point textures support 6 decimal places of precision
+     *
+     * @private
+     */
+    function checkFloatTexturePrecision(context) {
+        if (!context.floatingPointTexture) {
+            return false;
+        }
+
+        var computeEngine = new ComputeEngine(context);
+        var outputTexture = new Texture({
+            context : context,
+            width : 1,
+            height : 1,
+            pixelFormat : PixelFormat.RGBA
+        });
+
+        var floatTexture = new Texture({
+            context : context,
+            width : 1,
+            height : 1,
+            pixelFormat : PixelFormat.RGBA,
+            pixelDatatype : checkFloatTexturePrecision._getFloatPixelType(),
+            source : {
+                width : 1,
+                height : 1,
+                arrayBufferView : checkFloatTexturePrecision._getArray([123456, 0, 0, 0])
+            }
+        });
+
+        var framebuffer = new Framebuffer({
+            context : context,
+            colorTextures : [outputTexture],
+            destroyAttachments : false
+        });
+
+        var readState = {
+            framebuffer : framebuffer,
+            x : 0,
+            y : 0,
+            width : 1,
+            height : 1
+        };
+
+        var sixPlaces = false;
+        var computeCommand = new ComputeCommand({
+            fragmentShaderSource : CheckFloatTexturePrecisionFS,
+            outputTexture : outputTexture,
+            uniformMap : {
+                u_floatTexture : function() {
+                    return floatTexture;
+                }
+            },
+            persists : false,
+            postExecute : function() {
+                var pixel = context.readPixels(readState);
+                sixPlaces = pixel[0] === 0;
+            }
+        });
+
+        computeCommand.execute(computeEngine);
+
+        computeEngine.destroy();
+        framebuffer.destroy();
+
+        return sixPlaces;
+    }
+
+    checkFloatTexturePrecision._getFloatPixelType = function() {
+        return PixelDatatype.FLOAT;
+    };
+
+    checkFloatTexturePrecision._getArray = function(array) {
+        return new Float32Array(array);
+    };
+
+    return checkFloatTexturePrecision;
+});

Source/Scene/ClassificationPrimitive.js

@@ -578,7 +578,7 @@ define([
         });
         var attributeLocations = classificationPrimitive._primitive._attributeLocations;
 
-        var shadowVolumeAppearance = new ShadowVolumeAppearance(cullFragmentsUsingExtents, planarExtents, classificationPrimitive.appearance);
+        var shadowVolumeAppearance = new ShadowVolumeAppearance(cullFragmentsUsingExtents, planarExtents, classificationPrimitive.appearance, context.floatTextureSixPlaces);
 
         classificationPrimitive._spStencil = ShaderProgram.replaceCache({
             context : context,

Source/Scene/GroundPrimitive.js

@@ -730,10 +730,11 @@ define([
                     var boundingRectangle = getRectangle(frameState, geometry);
                     var textureCoordinateRotationPoints = geometry.textureCoordinateRotationPoints;
 
+                    var useFloatBatchTable = frameState.context.floatTextureSixPlaces;
                     if (usePlanarExtents) {
-                        attributes = ShadowVolumeAppearance.getPlanarTextureCoordinateAttributes(boundingRectangle, textureCoordinateRotationPoints, ellipsoid, frameState.mapProjection, this._maxHeight);
+                        attributes = ShadowVolumeAppearance.getPlanarTextureCoordinateAttributes(boundingRectangle, textureCoordinateRotationPoints, ellipsoid, frameState.mapProjection, useFloatBatchTable, this._maxHeight);
                     } else {
-                        attributes = ShadowVolumeAppearance.getSphericalExtentGeometryInstanceAttributes(boundingRectangle, textureCoordinateRotationPoints, ellipsoid, frameState.mapProjection);
+                        attributes = ShadowVolumeAppearance.getSphericalExtentGeometryInstanceAttributes(boundingRectangle, textureCoordinateRotationPoints, ellipsoid, frameState.mapProjection, useFloatBatchTable);
                     }
 
                     var instanceAttributes = instance.attributes;