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Normal generation errors #5032

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Feb 24, 2017
Merged

Normal generation errors #5032

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b264931
Fix issue where we can't generate correct normals. Triangles are eith…
Feb 23, 2017
37d0c47
Tweak.
Feb 24, 2017
b33ff44
Tweak.
Feb 24, 2017
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26 changes: 17 additions & 9 deletions Source/Core/GeometryPipeline.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1173,20 +1173,28 @@ define([
for (i = 0; i < numVertices; i++) {
var i3 = i * 3;
vertexNormalData = normalsPerVertex[i];
Cartesian3.clone(Cartesian3.ZERO, normal);
if (vertexNormalData.count > 0) {
Cartesian3.clone(Cartesian3.ZERO, normal);
for (j = 0; j < vertexNormalData.count; j++) {
Cartesian3.add(normal, normalsPerTriangle[normalIndices[vertexNormalData.indexOffset + j]], normal);
}
Cartesian3.normalize(normal, normal);
normalValues[i3] = normal.x;
normalValues[i3 + 1] = normal.y;
normalValues[i3 + 2] = normal.z;
} else {
normalValues[i3] = 0.0;
normalValues[i3 + 1] = 0.0;
normalValues[i3 + 2] = 1.0;

// We can run into an issue where a vertex is used with 2 primitives that have opposite winding order.
if (Cartesian3.equals(Cartesian3.ZERO, normal)) {
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You might have more than 2 triangles. Would a better test be to only add a normal if its dot product with the sum is greater than zero?

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Actually, never mind. I can think of some geometries that Cesium can generate where this wouldn't be true. Also, add an epsilon check here.

Cartesian3.clone(normalsPerTriangle[normalIndices[vertexNormalData.indexOffset]], normal);
}
}

// We end up with a zero vector probably because of a degenerate triangle
if (Cartesian3.equals(Cartesian3.ZERO, normal)) {
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Use an epsilon check.

// Default to (0,0,1)
normal.z = 1.0;
}

Cartesian3.normalize(normal, normal);
normalValues[i3] = normal.x;
normalValues[i3 + 1] = normal.y;
normalValues[i3 + 2] = normal.z;
}

geometry.attributes.normal = new GeometryAttribute({
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44 changes: 44 additions & 0 deletions Specs/Core/GeometryPipelineSpec.js
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Expand Up @@ -1410,6 +1410,50 @@ defineSuite([
expect(Cartesian3.fromArray(normals, 18)).toEqualEpsilon(Cartesian3.negate(Cartesian3.UNIT_Z, new Cartesian3()), CesiumMath.EPSILON7);
});

it('computeNormal computes normal of (0,0,1) for a degenerate triangle', function() {
var geometry = new Geometry({
attributes: {
position: new GeometryAttribute({
values: [0, 0, 0, 1, 0, 0],
componentsPerAttribute: 3,
componentDatatype : ComponentDatatype.FLOAT
})
},
indices : [0, 1, 0],
primitiveType: PrimitiveType.TRIANGLES
});

geometry = GeometryPipeline.computeNormal(geometry);

expect(geometry.attributes.normal.values.length).toEqual(2*3);
expect(geometry.attributes.normal.values).toEqual([0, 0, 1, 0, 0, 1]);
});

it('computeNormal takes first normal for two coplanar triangles with opposite winding orders', function() {
var geometry = new Geometry({
attributes: {
position: new GeometryAttribute({
values: [0, 0, 0, 1, 0, 1, 1, 1, 1],
componentsPerAttribute: 3,
componentDatatype : ComponentDatatype.FLOAT
})
},
indices : [0, 1, 2, 2, 1, 0],
primitiveType: PrimitiveType.TRIANGLES
});

geometry = GeometryPipeline.computeNormal(geometry);

var normals = geometry.attributes.normal.values;
expect(normals.length).toEqual(3*3);

var a = Cartesian3.normalize(new Cartesian3(-1, 0, 1), new Cartesian3());

expect(Cartesian3.fromArray(normals, 0)).toEqualEpsilon(a, CesiumMath.EPSILON7);
expect(Cartesian3.fromArray(normals, 3)).toEqualEpsilon(a, CesiumMath.EPSILON7);
expect(Cartesian3.fromArray(normals, 6)).toEqualEpsilon(a, CesiumMath.EPSILON7);
});

it('computeTangentAndBitangent throws when geometry is undefined', function() {
expect(function() {
GeometryPipeline.computeTangentAndBitangent();
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