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Fix oct-encoded normal upsampling. #1961

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merged 12 commits into from
Jul 27, 2014
Merged

Fix oct-encoded normal upsampling. #1961

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a678cd9
Fix normal upsampling. Cannot linearly interpolate oct encoded norma…
abwood Jul 24, 2014
a59d9ee
Moved octEncoding into Core. Moved signNotZero and toSNorm into Cesi…
abwood Jul 25, 2014
393df80
Minor cleanup. Added new conversion function to Math.js, fromSNorm.
abwood Jul 25, 2014
e670ac7
Minor cleanup.
abwood Jul 25, 2014
7129514
Merge remote-tracking branch 'agi/master' into upsampleQuantizedMeshN…
abwood Jul 25, 2014
93fdefa
Doc updates.
abwood Jul 25, 2014
95ef5bb
Cleaned up doc for Oct.
abwood Jul 25, 2014
fc60338
Fixed typo in doc.
abwood Jul 25, 2014
fae0d2f
Documented exceptions in Oct.
abwood Jul 26, 2014
c2d8b85
Mark Oct class as private.
abwood Jul 26, 2014
05058ad
Merge remote-tracking branch 'agi/master' into upsampleQuantizedMeshN…
abwood Jul 26, 2014
9630474
Minor cleanup.
abwood Jul 27, 2014
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70 changes: 68 additions & 2 deletions Source/Workers/upsampleQuantizedTerrainMesh.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
/*global define*/
define([
'../Core/BoundingSphere',
'../Core/Cartesian2',
'../Core/Cartesian3',
'../Core/Cartographic',
'../Core/defined',
Expand All @@ -11,6 +12,7 @@ define([
'./createTaskProcessorWorker'
], function(
BoundingSphere,
Cartesian2,
Cartesian3,
Cartographic,
defined,
Expand Down Expand Up @@ -372,18 +374,82 @@ define([
return CesiumMath.lerp(this.first.getV(), this.second.getV(), this.ratio);
};

function signNotZero(v) {
return v < 0.0 ? -1.0 : 1.0;
}

function toSNorm(f) {
return Math.round((f * 0.5 + 0.5) * 255.0);
}

function octDecode(x, y, result) {
result.x = x / 255.0 * 2.0 - 1.0;
result.y = y / 255.0 * 2.0 - 1.0;
result.z = 1.0 - (Math.abs(result.x) + Math.abs(result.y));

if (result.z < 0.0)
{
var oldVX = x / 255.0 * 2.0 - 1.0;
result.x = (1.0 - Math.abs(result.y)) * signNotZero(oldVX);
result.y = (1.0 - Math.abs(oldVX)) * signNotZero(result.y);
}

return Cartesian3.normalize(result, result);
}

function octEncode(vector, out) {
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Can you make this a generic unit-tested function (even if it is @private) since we are going to want it for the geometry pipeline, which we are going to start work on again soon for KML? Perhaps it is a function Cartesian3? Or perhaps it is better to make a new oct class and put static decode and encode functions in it.

signNotZero and toSNorm could probably go in Math.js.

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I'd be happy to. I was on the fence about moving these into Core in this pull request since it is currently only used in this location.

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At least the geometry pipeline will also use them. Probably dynamic buffers too if it is a win (I bet yes) ( #932). I could also see billboards using something similar for vertex compression ( #419). 3D models will also use this (but won't need the code since it will be done server-side).

out.x = vector.x / (Math.abs(vector.x) + Math.abs(vector.y) + Math.abs(vector.z));
out.y = vector.y / (Math.abs(vector.x) + Math.abs(vector.y) + Math.abs(vector.z));
if (vector.z < 0) {
var x = out.x;
var y = out.y;
out.x = (1.0 - Math.abs(y)) * signNotZero(x);
out.y = (1.0 - Math.abs(x)) * signNotZero(y);
}

out.x = toSNorm(out.x);
out.y = toSNorm(out.y);
}

var encodedScratch = new Cartesian2();
// An upsampled triangle may be clipped twice before it is assigned an index
// In this case, we need a buffer to handle the recursion of getNormalX() and getNormalY().
var depth = -1;
var cartesianScratch1 = [new Cartesian3(), new Cartesian3()];
var cartesianScratch2 = [new Cartesian3(), new Cartesian3()];
function lerpOctEncodedNormal(vertex, result) {
depth += 1;

var first = cartesianScratch1[depth];
var second = cartesianScratch2[depth];

first = octDecode(vertex.first.getNormalX(), vertex.first.getNormalY(), first);
second = octDecode(vertex.second.getNormalX(), vertex.second.getNormalY(), second);
cartesian3Scratch = Cartesian3.lerp(first, second, vertex.ratio, cartesian3Scratch);

octEncode(cartesian3Scratch, result);

depth -= 1;
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Nitpicky, but why not --depth (and similar above)?


return result;
}

Vertex.prototype.getNormalX = function() {
if (defined(this.index)) {
return this.normalBuffer[this.index * 2];
}
return Math.round(CesiumMath.lerp(this.first.getNormalX(), this.second.getNormalX(), this.ratio));

encodedScratch = lerpOctEncodedNormal(this, encodedScratch);
return encodedScratch.x;
};

Vertex.prototype.getNormalY = function() {
if (defined(this.index)) {
return this.normalBuffer[this.index * 2 + 1];
}
return Math.round(CesiumMath.lerp(this.first.getNormalY(), this.second.getNormalY(), this.ratio));

encodedScratch = lerpOctEncodedNormal(this, encodedScratch);
return encodedScratch.y;
};

var polygonVertices = [];
Expand Down
76 changes: 76 additions & 0 deletions Specs/Core/QuantizedMeshTerrainDataSpec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -143,6 +143,82 @@ defineSuite([
});
});

it('oct-encoded normals works for all four children of a simple quad', function() {
var data = new QuantizedMeshTerrainData({
minimumHeight : 0.0,
maximumHeight : 4.0,
quantizedVertices : new Uint16Array([ // order is sw nw se ne
// u
0, 0, 32767, 32767,
// v
0, 32767, 0, 32767,
// heights
32767 / 4.0, 2.0 * 32767 / 4.0, 3.0 * 32767 / 4.0, 32767
]),
encodedNormals : new Uint8Array([
// fun property of oct-encoded normals: the octrahedron is projected onto a plane
// and unfolded into a unit square. The 4 corners of this unit square are encoded values
// of the same Cartesian normal, vec3(0.0, 0.0, 1.0).
// Therefore, all 4 normals below are actually oct-encoded representations of vec3(0.0, 0.0, 1.0)
255, 0, // sw
255, 255, // nw
255, 0, // se
255, 255 // ne
]),
indices : new Uint16Array([
0, 3, 1,
0, 2, 3
]),
boundingSphere : new BoundingSphere(),
horizonOcclusionPoint : new Cartesian3(),
westIndices : [],
southIndices : [],
eastIndices : [],
northIndices : [],
westSkirtHeight : 1.0,
southSkirtHeight : 1.0,
eastSkirtHeight : 1.0,
northSkirtHeight : 1.0,
childTileMask : 15
});

var tilingScheme = new GeographicTilingScheme();

var swPromise = data.upsample(tilingScheme, 0, 0, 0, 0, 0, 1);
var sePromise = data.upsample(tilingScheme, 0, 0, 0, 1, 0, 1);
var nwPromise = data.upsample(tilingScheme, 0, 0, 0, 0, 1, 1);
var nePromise = data.upsample(tilingScheme, 0, 0, 0, 1, 1, 1);

var upsampleResults;

when.all([swPromise, sePromise, nwPromise, nePromise], function(results) {
upsampleResults = results;
});

waitsFor(function() {
return defined(upsampleResults);
});

runs(function() {
expect(upsampleResults.length).toBe(4);

for (var i = 0; i < upsampleResults.length; ++i) {
var upsampled = upsampleResults[i];
expect(upsampled).toBeDefined();

var encodedNormals = upsampled._encodedNormals;

expect(encodedNormals.length).toBe(8);

// All 4 normals should remain oct-encoded representations of vec3(0.0, 0.0, 1.0)
for (var n = 0; n < encodedNormals.length; ++n) {
expect(encodedNormals[i]).toBe(255);
}
}
});

});

it('works for a quad with an extra vertex in the northwest child', function() {
var data = new QuantizedMeshTerrainData({
minimumHeight : 0.0,
Expand Down