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light: split GLM_PolyRandomPoint into precomputed portion 

take uniform random params explicitly
This commit is contained in:
Eric Wasylishen 2017-11-24 17:31:54 -07:00
parent 92bacbe7e1
commit d4d2d537eb
3 changed files with 32 additions and 12 deletions
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29
common/mathlib.cc
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@ -613,11 +613,10 @@ qvec3f GLM_PolyCentroid(const std::vector<qvec3f> &points)
return poly_centroid;
}
qvec3f GLM_PolyRandomPoint(const std::vector<qvec3f> &points)
poly_random_point_state_t GLM_PolyRandomPoint_Setup(const std::vector<qvec3f> &points)
{
Q_assert(points.size() >= 3);
// FIXME: Precompute this
float poly_area = 0;
std::vector<float> triareas;
@ -632,18 +631,28 @@ qvec3f GLM_PolyRandomPoint(const std::vector<qvec3f> &points)
triareas.push_back(triarea);
poly_area += triarea;
}
// Pick a random triangle, with probability proportional to triangle area
const float uniformRandom = Random();
const std::vector<float> cdf = MakeCDF(triareas);
const int whichTri = SampleCDF(cdf, uniformRandom);
Q_assert(whichTri >= 0 && whichTri < triareas.size());
poly_random_point_state_t result;
result.points = points;
result.triareas = triareas;
result.triareas_cdf = cdf;
return result;
}
const tri_t tri { points.at(0), points.at(1 + whichTri), points.at(2 + whichTri) };
// r1, r2, r3 must be in [0, 1]
qvec3f GLM_PolyRandomPoint(const poly_random_point_state_t &state, float r1, float r2, float r3)
{
// Pick a random triangle, with probability proportional to triangle area
const float uniformRandom = r1;
const int whichTri = SampleCDF(state.triareas_cdf, uniformRandom);
Q_assert(whichTri >= 0 && whichTri < state.triareas.size());
const tri_t tri { state.points.at(0), state.points.at(1 + whichTri), state.points.at(2 + whichTri) };
// Pick random barycentric coords.
const qvec3f bary = Barycentric_Random(Random(), Random());
const qvec3f bary = Barycentric_Random(r2, r3);
const qvec3f point = Barycentric_ToPoint(bary, tri);
return point;

11
include/common/mathlib.hh
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@ -336,7 +336,16 @@ std::pair<bool, qvec3f> GLM_InterpolateNormal(const std::vector<qvec3f> &points,
std::vector<qvec3f> GLM_ShrinkPoly(const std::vector<qvec3f> &poly, const float amount);
/// Returns (front part, back part)
std::pair<std::vector<qvec3f>,std::vector<qvec3f>> GLM_ClipPoly(const std::vector<qvec3f> &poly, const qvec4f &plane);
qvec3f GLM_PolyRandomPoint(const std::vector<qvec3f> &points);
class poly_random_point_state_t {
public:
std::vector<qvec3f> points;
std::vector<float> triareas;
std::vector<float> triareas_cdf;
};
poly_random_point_state_t GLM_PolyRandomPoint_Setup(const std::vector<qvec3f> &points);
qvec3f GLM_PolyRandomPoint(const poly_random_point_state_t &state, float r1, float r2, float r3);
/// projects p onto the vw line.
/// returns 0 for p==v, 1 for p==w

4
light/test_light.cc
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@ -514,9 +514,11 @@ TEST(mathlib, RandomPointInPoly) {
qvec3f max(-FLT_MAX);
qvec3f avg(0);
const auto randomstate = GLM_PolyRandomPoint_Setup(poly);
const int N=100;
for (int i=0; i<N; i++) {
const qvec3f point = GLM_PolyRandomPoint(poly);
const qvec3f point = GLM_PolyRandomPoint(randomstate, Random(), Random(), Random());
ASSERT_TRUE(GLM_EdgePlanes_PointInside(edgeplanes, point));
//std::cout << "point: " << qv::to_string(point) << std::endl;