Add support to check children bounds for visibility before selecting a tile #4978

austinEng · 2017-02-09T21:16:40Z

Todo:

Testing and profiling for performance. Initial tests show about 0ms slowdown, with a few MB less downloaded data, and a big reduction in draw calls.
Unit tests

pjcozzi · 2017-02-09T22:40:40Z

Part of #3241

pjcozzi · 2017-02-09T22:47:10Z

Source/Scene/Cesium3DTileOptimizations.js

+     * @param {Boolean} [force=false] Whether to always evaluate support for the childrenWithinParent optimization
+     * @returns {Boolean} Whether the childrenWithinParent optimization is supported.
+     */
+    Cesium3DTileOptimizations.prototype.checkChildrenWithinParent = function(tile, evaluate, force) {


Depending on your tests, we may end up removing this, e.g., if the new CPU overhead is trivial and/or it is a win for most datasets.

If either of the above is true, we may just do it all the time and even avoid include hints in the tileset.

I think we can probably just check this every time. In practice, we only need to evaluate it once per tile (unless tiles move relative to their parent?). So really, this is just a small one-time cost on load.

It's not about load time performance, it's about client-side complexity.

My point is that writing a general test for this taking into account all the different bounding volume types (basically it is CSG union) could be a lot of work to write, test, etc. Maybe there are some heuristics to simplify this by putting boxes around regions and using a cost function dependent on the number of children.

I dunno, could be complicated.

So we might just skip this completely on the client if the tileset contains a hint to do it or not, or if always checking the children is fast/useful enough.

pjcozzi · 2017-02-09T22:47:49Z

In addition to testing terrain, cities, and design models, @lilleyse can you provide a massive point cloud dataset for testing?

pjcozzi · 2017-02-09T22:50:10Z

Source/Scene/Cesium3DTileset.js

                if ((sse <= maximumScreenSpaceError) || (childrenLength === 0)) {
                    // This tile meets the SSE so add its commands.
                    // Select tile if it's a leaf (childrenLength === 0)
-                    selectTile(tileset, t, fullyVisible, frameState);
+                    if (useChildrenBoundUnion) {


Are you sure this is the right place to add this code? I was expecting a place that use to have

checkThisTilesVolume

to be replaced with

checkTheUnionOfTheTilesChildsVolumes

pjcozzi · 2017-02-09T22:53:19Z

Source/Scene/Cesium3DTileset.js

@@ -1311,50 +1372,47 @@ define([
                    }

                    if (!allChildrenLoaded) {
-                        // Tile does not meet SSE.  Add its commands since it is the best we have and request its children.
-                        selectTile(tileset, t, fullyVisible, frameState);
+                        childrenVisibility = computeChildrenVisibility(t, frameState, false);


Why isn't useChildrenBoundUnion called before computeChildrenVisibility to save the CPU overhead when it isn't needed?

Thanks, good catch

…a tile

austinEng · 2017-02-10T20:50:55Z

Some test results: these represent the deltas between original and optimized versions of the code. i.e (original - optimized)

	Requests	MB	Tiles Selected	Draw Commands	MS
Philly 3/4 View	2	0.1	1	1	0
Philly Top-Down	30	1.2	6	6	0
Philly Street	34	0.9	5	5	-0.1
Rio 3/4 View	22	0.5	6	13	0.2
Rio Mountains	33	1.5	2	6	0.2
Rio Downhill	4	0.1	2	4	0

Philly 3/4 View

2 fewer requests
0.1 fewer MB
1 fewer draw commands
0 ms slower per frame

Philly Top-Down

30 fewer requests
1.2 fewer MB
6 fewer draw commands
0 ms slower per frame

This optimization seems to be most effective for culling large tiles mostly behind the camera

Philly Street

34 fewer requests
0.9 fewer MB
5 fewer draw commands
0.1 ms slower per frame

Rio 3/4 View

22 fewer requests
0.5 fewer MB
13 fewer draw commands
0.2 ms faster per frame

Rio Mountains

33 fewer requests
1.5 fewer MB
6 fewer draw commands
0.2 ms faster per frame

Rio Downhill

4 fewer requests
0.1 fewer MB
4 fewer draw commands
0 ms slower per frame

pjcozzi · 2017-02-10T22:17:10Z

Source/Scene/Cesium3DTile.js

+         *
+         * @private
+         */
+        this.childrenVisibility = 1;


Instead of assigning to 1, ChildrenVisibilityFlags should be in its own file (it can be @private) and declared like other Cesium enums. For example, see Cesium3DTileContentState.js.

pjcozzi · 2017-02-10T22:18:56Z

Source/Scene/Cesium3DTileOptimizations.js

+     *
+     * Flag denoting support for a 3D Tiles optimization
+     */
+    var Cesium3DTileOptimizationFlag = {


This should also be @private in its own file.

Also, we generally don't suffix enums with Flag or Flags. Perhaps there are better names for these.

pjcozzi · 2017-02-10T22:20:16Z

Source/Scene/Cesium3DTileOptimizations.js

+     * Flag denoting support for a 3D Tiles optimization
+     */
+    var Cesium3DTileOptimizationFlag = {
+        UNSUPPORTED: 0,


Perhaps rename these to:

NOT_COMPUTED USE_OPTIMIZATION SKIP_OPTIMIZATION

In Cesium, "supported" usually refers to WebGL features.

pjcozzi · 2017-02-10T22:20:35Z

Source/Scene/Cesium3DTileOptimizations.js

+     *     })
+     * });
+     */
+    function Cesium3DTileOptimizations(options) {


In the doc, this should be @private.

pjcozzi · 2017-02-10T22:21:27Z

Source/Scene/Cesium3DTileOptimizations.js

+
+    /**
+     * Defines optional optimization flags for a {@link Cesium3DTileset}.
+     * Optimizations marked as Cesium3DTileOptimizations.Flags.SUPPORTED or Cesium3DTileOptimizations.Flags.UNSUPPORTED


Use {@link } when referring to enums.

For more, see the doc guide.

pjcozzi · 2017-02-10T22:24:07Z

Source/Scene/Cesium3DTileset.js

@@ -270,7 +274,8 @@ define([
            lastColor : new Cesium3DTilesetStatistics(),
            lastPick : new Cesium3DTilesetStatistics()
        };
-
+
+        this._optimizations = defaultValue(options.optimizations, new Cesium3DTileOptimizations());


Just remove this for now until we decide on CesiumGS/3d-tiles#176

pjcozzi · 2017-02-10T22:25:11Z

Source/Scene/Cesium3DTileOptimizations.js

+        evaluate = defaultValue(evaluate, false);
+        force = defaultValue(force, false);
+
+        if ((this.childrenWithinParent === Cesium3DTileOptimizations.Flags.INDETERMINATE && evaluate) || force) {


Just a reminder to comment this function as we discussed offline.

pjcozzi · 2017-02-10T22:29:06Z

Source/Scene/Cesium3DTileset.js

@@ -1285,11 +1336,21 @@ define([
                // With replacement refinement, if the tile's SSE
                // is not sufficient, its children (or ancestors) are
                // rendered instead
+                var useChildrenBoundUnion = t._optimizations.checkChildrenWithinParent(t, true);


This workflow is a bit awkward. Can we just compute this on load and then just check a boolean property here?

Longer-term, this is the type of processing that would be in a web worker when a tile is downloaded and before it is ready to render.

pjcozzi · 2017-02-10T22:37:42Z

Please unit test this carefully including cases with request volumes.

austinEng · 2017-02-14T14:54:58Z

@pjcozzi Updated. I believe the failing tests should be fixed after this

pjcozzi · 2017-02-15T02:52:08Z

Source/Scene/Cesium3DTileOptimizations.js

+     * @alias Cesium3DTileOptimizations
+     * @constructor
+     */
+    function Cesium3DTileOptimizations(options) {


To avoid some indirection at runtime (and likely cache misses), consider replacing with with a boolean property on the tile. So file would just contain a single function for checkChildrenWithinParent.

In time, the boolean would probably become a bitmask with many booleans for different optimizations and tiles would more cohesively fit into cache lines (I'm not saying that they do today, but this extra indirection does not help the case).

pjcozzi · 2017-02-15T02:52:20Z

Source/Scene/Cesium3DTileset.js

@@ -270,7 +276,7 @@ define([
            lastColor : new Cesium3DTilesetStatistics(),
            lastPick : new Cesium3DTilesetStatistics()
        };
-
+        


Extra whitespace.

pjcozzi · 2017-02-15T02:53:00Z

@lilleyse can you review this?

lilleyse

The code here looks good and organized. I tested with a few different tilesets and haven't noticed any issues.

lilleyse · 2017-02-17T16:11:18Z

Source/Scene/Cesium3DTileOptimizations.js

+        '../Core/freezeObject',
+        './Cesium3DTileOptimizationHint',
+        './TileOrientedBoundingBox',
+        './TileBoundingRegion'


Flip these two (alphabetical ordering)

lilleyse · 2017-02-17T16:11:30Z

Source/Scene/Cesium3DTileOptimizations.js

+    'use strict';
+
+    /**
+     * Utiility functions for computing optimization hints for a {@link Cesium3DTileset}.


Utiility typo

lilleyse · 2017-02-17T16:12:24Z

Source/Scene/Cesium3DTileOptimizations.js

+            }
+        }
+
+        return tile._optimChildrenWithinParent === Cesium3DTileOptimizationHint.USE_OPTIMIZATION ? true : false;


Why not just return tile._optimChildrenWithinParent === Cesium3DTileOptimizationHint.USE_OPTIMIZATION;

lilleyse · 2017-02-17T16:14:13Z

Source/Scene/Cesium3DTileOptimizations.js

+     * spheres are not supported for the reason that the child bounds can very often be partially outside of the parent bounds.
+     *
+     * @param {Cesium3DTile} tile The tile to check.
+     * @param {Boolean} [evaluate=false] Whether to evaluate support if support for the childrenWithinParent optimization is Cesium3DTileOptimizations.Hints.NOT_COMPUTED


Fix wording here.

Cesium3DTileOptimizations.Hints should be Cesium3DTileOptimizationHints

lilleyse · 2017-02-17T16:16:11Z

Source/Scene/Cesium3DTileOptimizations.js

+     */
+    Cesium3DTileOptimizations.checkChildrenWithinParent = function(tile, evaluate, force) {
+        evaluate = defaultValue(evaluate, false);
+        force = defaultValue(force, false);


Throw DeveloperError if tile is undefined.

lilleyse · 2017-02-17T17:08:31Z

Source/Scene/Cesium3DTileset.js

+                        }
+                    } else {
+                        selectTile(tileset, t, fullyVisible, frameState);
+                    }


Given these updates, it may be cleaner to separate out the childrenLength === 0 and put it before the sse <= maximumScreenSpaceError check.

lilleyse · 2017-02-17T20:37:19Z

Source/Scene/Cesium3DTileset.js

+                        if (useChildrenBoundUnion) {
+                            childrenVisibility = computeChildrenVisibility(t, frameState, false);
+                        }
+                        if (!useChildrenBoundUnion || (childrenVisibility & Cesium3DTileChildrenVisibility.VISIBLE) || childrenLength === 0) {


No need to check childrenLength === 0 here.

Same applies to a few other areas.

lilleyse · 2017-02-17T20:51:01Z

Specs/Scene/Cesium3DTilesetSpec.js

@@ -840,6 +845,158 @@ defineSuite([
        });
    });

+    describe('children bound union optimization', function() {
+        it ('does not select visible tiles with invisible children', function() {


it ( -> it(

lilleyse · 2017-02-17T20:52:04Z

Specs/Scene/Cesium3DTilesetSpec.js

+        it ('does not select visible tiles not meeting SSE with visible children', function() {
+            return Cesium3DTilesTester.loadTileset(scene, tilesetReplacementWithViewerRequestVolumeUrl).then(function(tileset) {
+                var root = tileset._root;
+                var child_root = root.children[0];


Use camel case instead.

lilleyse · 2017-02-17T20:55:14Z

Specs/Data/Cesium3DTiles/Tilesets/TilesetReplacementWithViewerRequestVolume/tileset.json

@@ -0,0 +1,174 @@
+{


Can you open a PR into https://github.com/AnalyticalGraphicsInc/3d-tiles-tools/tree/master/generator that adds this tileset?

lilleyse · 2017-02-17T21:17:41Z

In addition to testing terrain, cities, and design models, @lilleyse can you provide a massive point cloud dataset for testing?

I don't actually have a massive point cloud that does replacement refinement...

pjcozzi · 2017-02-18T15:55:50Z

I don't actually have a massive point cloud that does replacement refinement...

OK, we should be fine here.

@austinEng can you merge in 3d-tiles and fix the conflicts?

@lilleyse please merge when ready and check this off the roadmap, #3241

austinEng · 2017-02-20T15:54:02Z

@lilleyse updated

lilleyse · 2017-02-21T14:43:37Z

Source/Scene/Cesium3DTileset.js

+                    // This tile meets the SSE so add its commands.
+                    if (useChildrenBoundUnion) {
+                        childrenVisibility = computeChildrenVisibility(t, frameState, false);
+                        if ((childrenVisibility & Cesium3DTileChildrenVisibility.VISIBLE) || childrenLength === 0) {


Remove childrenLength === 0

lilleyse · 2017-02-21T14:53:29Z

Source/Scene/Cesium3DTileset.js

-                                    // and this tile can refine to them.
-                                    touch(tileset, child, outOfCore);
+                            if (outOfCore) {
+                                for (k = 0; (k < childrenLength) && t.canRequestContent(); ++k) {


This area was probably missed in the merge conflict resolution, but make sure to fix it with the changes from here: https://github.com/AnalyticalGraphicsInc/cesium/pull/5008/files

austinEng · 2017-02-21T16:33:41Z

@lilleyse updated

lilleyse · 2017-02-22T16:30:35Z

Alright, everything looks good here now.

pjcozzi reviewed Feb 9, 2017

View reviewed changes

austinEng added 2 commits February 10, 2017 08:20

add support to check children bounds for visibility before selecting …

3c8543d

…a tile

check useChildrenBoundUnion before computing visibility

721ca18

austinEng force-pushed the union-children-bounds branch from c8e7d43 to 721ca18 Compare February 10, 2017 20:25

pjcozzi reviewed Feb 10, 2017

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pjcozzi mentioned this pull request Feb 10, 2017

Hints for culling optimizations CesiumGS/3d-tiles#176

Closed

pjcozzi reviewed Feb 10, 2017

View reviewed changes

austinEng added 4 commits February 13, 2017 15:29

update comments, documentation, and code style

ac2ec9b

add tests

7fce7f1

remove extra require

fda059d

update tests

cd0ff90

austinEng force-pushed the union-children-bounds branch from 7cb5b40 to cd0ff90 Compare February 13, 2017 20:51

austinEng added 2 commits February 13, 2017 16:17

update tests

408c9ae

update tileset for specs

8a465a5

pjcozzi mentioned this pull request Feb 14, 2017

Add number of points/features stats to 3D Tiles Inspector #5003

Closed

Merge remote-tracking branch 'agi/3d-tiles' into union-children-bounds

e8b17c9

pjcozzi reviewed Feb 15, 2017

View reviewed changes

austinEng added 4 commits February 15, 2017 09:39

add culling stats

acd6b90

Merge remote-tracking branch 'agi/3d-tiles' into union-children-bounds

f8447c1

update documentation

5b1f387

simplify storage of optimization hints

12b9112

austinEng force-pushed the union-children-bounds branch 2 times, most recently from c607a56 to 61c9567 Compare February 15, 2017 17:29

syntax

9072938

austinEng force-pushed the union-children-bounds branch from 61c9567 to 9072938 Compare February 15, 2017 17:31

remove unused getter

b0afd4e

lilleyse reviewed Feb 17, 2017

View reviewed changes

austinEng added 2 commits February 20, 2017 10:39

updates

103d4e2

Merge remote-tracking branch 'agi/3d-tiles' into union-children-bounds

cb8a206

generate test tileset with 3d-tiles-tools

3607220

austinEng mentioned this pull request Feb 20, 2017

add replacement with viewer request volume tileset CesiumGS/3d-tiles-validator#54

Merged

pjcozzi mentioned this pull request Feb 21, 2017

Culling / OBB optimizations #2861

Open

2 tasks

lilleyse reviewed Feb 21, 2017

View reviewed changes

fix merge resolution

b6b91b5

Merge remote-tracking branch 'agi/3d-tiles' into union-children-bounds

a010e32

lilleyse merged commit 8ccf772 into CesiumGS:3d-tiles Feb 22, 2017

kring mentioned this pull request May 31, 2022

Use child tile bounding volumes to cull parent tiles CesiumGS/cesium-native#506

Closed

Add support to check children bounds for visibility before selecting a tile #4978

Add support to check children bounds for visibility before selecting a tile #4978

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austinEng commented Feb 9, 2017 • edited

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austinEng commented Feb 10, 2017

Philly 3/4 View

Philly Top-Down

Philly Street

Rio 3/4 View

Rio Mountains

Rio Downhill

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lilleyse commented Feb 17, 2017

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austinEng commented Feb 21, 2017

lilleyse commented Feb 22, 2017

austinEng commented Feb 9, 2017 •

edited