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// Copyright 2009-2020 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
#pragma once
namespace embree
{
namespace isa
{
/*! Intersects a ray with a quad with backface culling
* enabled. The quad v0,v1,v2,v3 is split into two triangles
* v0,v1,v3 and v2,v3,v1. The edge v1,v2 decides which of the two
* triangles gets intersected. */
template<int N>
__forceinline vbool<N> intersect_quad_backface_culling(const vbool<N>& valid0,
const Vec3fa& ray_org,
const Vec3fa& ray_dir,
const float ray_tnear,
const float ray_tfar,
const Vec3vf<N>& quad_v0,
const Vec3vf<N>& quad_v1,
const Vec3vf<N>& quad_v2,
const Vec3vf<N>& quad_v3,
vfloat<N>& u_o,
vfloat<N>& v_o,
vfloat<N>& t_o)
{
/* calculate vertices relative to ray origin */
vbool<N> valid = valid0;
const Vec3vf<N> O = Vec3vf<N>(ray_org);
const Vec3vf<N> D = Vec3vf<N>(ray_dir);
const Vec3vf<N> va = quad_v0-O;
const Vec3vf<N> vb = quad_v1-O;
const Vec3vf<N> vc = quad_v2-O;
const Vec3vf<N> vd = quad_v3-O;
const Vec3vf<N> edb = vb-vd;
const vfloat<N> WW = dot(cross(vd,edb),D);
const Vec3vf<N> v0 = select(WW <= 0.0f,va,vc);
const Vec3vf<N> v1 = select(WW <= 0.0f,vb,vd);
const Vec3vf<N> v2 = select(WW <= 0.0f,vd,vb);
/* calculate edges */
const Vec3vf<N> e0 = v2-v0;
const Vec3vf<N> e1 = v0-v1;
/* perform edge tests */
const vfloat<N> U = dot(cross(v0,e0),D);
const vfloat<N> V = dot(cross(v1,e1),D);
valid &= max(U,V) <= 0.0f;
if (unlikely(none(valid))) return false;
/* calculate geometry normal and denominator */
const Vec3vf<N> Ng = cross(e1,e0);
const vfloat<N> den = dot(Ng,D);
const vfloat<N> rcpDen = rcp(den);
/* perform depth test */
const vfloat<N> t = rcpDen*dot(v0,Ng);
valid &= vfloat<N>(ray_tnear) <= t & t <= vfloat<N>(ray_tfar);
if (unlikely(none(valid))) return false;
/* avoid division by 0 */
valid &= den != vfloat<N>(zero);
if (unlikely(none(valid))) return false;
/* update hit information */
t_o = t;
u_o = U * rcpDen;
v_o = V * rcpDen;
u_o = select(WW <= 0.0f,u_o,1.0f-u_o);
v_o = select(WW <= 0.0f,v_o,1.0f-v_o);
return valid;
}
}
}
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