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// Copyright 2009 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
#include "common/FeatureFlagsEnum.h"
#include "common/World.ih"
#include "math/random.ih"
#include "math/sampling.ih"
#include "render/util.ih"
OSPRAY_BEGIN_ISPC_NAMESPACE
SYCL_EXTERNAL float computeAO(const Renderer *uniform,
const World *uniform world,
const varying DifferentialGeometry &dg,
const uniform int sampleCnt,
const uniform float aoRadius,
const varying vec3i &sampleID,
const uniform FeatureFlagsHandler &ffh)
{
const uniform int accumID = reduce_max(sampleID.z) * sampleCnt;
// init TEA RNG //
RandomTEA rng_state;
varying RandomTEA *const uniform rng = &rng_state;
RandomTEA_Constructor(rng, sampleID.x, sampleID.y);
const vec2f rot = RandomTEA_getFloats(rng);
int hits = 0;
const linear3f localToWorld = frame(dg.Ns);
for (uniform int i = 0; i < sampleCnt; i++) {
// Use base-5 and base-7 Halton to avoid correlation with sample position
const vec2f halton = make_vec2f(
PermHalton_sample5(accumID + i), PermHalton_sample7(accumID + i));
const vec2f r = CranleyPattersonRotation(halton, rot);
const vec3f local_ao_dir = cosineSampleHemisphere(r);
const vec3f ao_dir = localToWorld * local_ao_dir;
if (dot(ao_dir, dg.Ns) < 0.01f) { // check below surface
hits++;
continue;
}
Ray ao_ray;
setRay(ao_ray, dg.P, ao_dir, dg.epsilon, aoRadius);
if (isOccluded(world, ao_ray, ffh))
hits++;
}
// the cosTheta of cosineSampleHemispherePDF and dot(shadingNormal, ao_dir)
// cancel
return 1.0f - (hits / (float)sampleCnt);
}
OSPRAY_END_ISPC_NAMESPACE
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