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//-*-c-*-
#ifndef __INTERSECT_H__
#define __INTERSECT_H__
#include <math_constants.h>
#include "linalg.h"
#include "matrix.h"
#include "rotate.h"
#define EPSILON 0.0f
/* Test the intersection between a ray starting from `origin` traveling in the
direction `direction` and a triangle defined by the vertices `v0`, `v1`, and
`v2`. If the ray intersects the triangle, set `distance` to the distance
between `origin` and the intersection and return true, else return false.
`direction` must be normalized. */
__device__ bool intersect_triangle(const float3 &origin, const float3 &direction, const float3 &v0, const float3 &v1, const float3 &v2, float &distance)
{
Matrix m = make_matrix(v1-v0, v2-v0, -direction);
float determinant = det(m);
if (determinant == 0.0f)
return false;
float3 b = origin-v0;
float u1 = ((m.a11*m.a22 - m.a12*m.a21)*b.x +
(m.a02*m.a21 - m.a01*m.a22)*b.y +
(m.a01*m.a12 - m.a02*m.a11)*b.z)/determinant;
if (u1 < -EPSILON || u1 > 1.0f)
return false;
float u2 = ((m.a12*m.a20 - m.a10*m.a22)*b.x +
(m.a00*m.a22 - m.a02*m.a20)*b.y +
(m.a02*m.a10 - m.a00*m.a12)*b.z)/determinant;
if (u2 < -EPSILON || u2 > 1.0f)
return false;
float u3 = ((m.a10*m.a21 - m.a11*m.a20)*b.x +
(m.a01*m.a20 - m.a00*m.a21)*b.y +
(m.a00*m.a11 - m.a01*m.a10)*b.z)/determinant;
if (u3 <= 0.0f || (1.0f-u1-u2) < -EPSILON)
return false;
distance = u3;
return true;
}
/* Return the 32 bit color associated with the intersection between a ray
starting from `origin` traveling in the direction `direction` and the
plane defined by the points `v0`, `v1`, and `v2` using the cosine of the
angle between the ray and the plane normal to determine the brightness.
`direction` must be normalized. */
__device__ unsigned int get_color(const float3 &direction, const float3 &v0, const float3& v1, const float3 &v2, const unsigned int base_color=0xFFFFFFFF)
{
float scale = dot(normalize(cross(v1-v0,v2-v1)),-direction);
unsigned int r = 0xFF & (base_color >> 16);
unsigned int g = 0xFF & (base_color >> 8);
unsigned int b = 0xFF & base_color;
if (scale < 0.0f)
scale = dot(-normalize(cross(v1-v0,v2-v1)),-direction);
r = floorf(r*scale);
g = floorf(g*scale);
b = floorf(b*scale);
return r << 16 | g << 8 | b;
}
/* Test the intersection between a ray starting from `origin` traveling in the
direction `direction` and the axis-aligned box defined by the opposite
vertices `lower_bound` and `upper_bound`. If the ray intersects the box
return True, else return False. */
__device__ bool intersect_box(const float3 &origin, const float3 &direction, const float3 &lower_bound, const float3 &upper_bound, float& distance_to_box)
{
float kmin, kmax, kymin, kymax, kzmin, kzmax;
float divx = 1.0f/direction.x;
if (divx >= 0.0f)
{
kmin = (lower_bound.x - origin.x)*divx;
kmax = (upper_bound.x - origin.x)*divx;
}
else
{
kmin = (upper_bound.x - origin.x)*divx;
kmax = (lower_bound.x - origin.x)*divx;
}
if (kmax < 0.0f)
return false;
float divy = 1.0f/direction.y;
if (divy >= 0.0f)
{
kymin = (lower_bound.y - origin.y)*divy;
kymax = (upper_bound.y - origin.y)*divy;
}
else
{
kymin = (upper_bound.y - origin.y)*divy;
kymax = (lower_bound.y - origin.y)*divy;
}
if (kymax < 0.0f)
return false;
if (kymin > kmin)
kmin = kymin;
if (kymax < kmax)
kmax = kymax;
if (kmin > kmax)
return false;
float divz = 1.0f/direction.z;
if (divz >= 0.0f)
{
kzmin = (lower_bound.z - origin.z)*divz;
kzmax = (upper_bound.z - origin.z)*divz;
}
else
{
kzmin = (upper_bound.z - origin.z)*divz;
kzmax = (lower_bound.z - origin.z)*divz;
}
if (kzmax < 0.0f)
return false;
if (kzmin > kmin)
kmin = kzmin;
if (kzmax < kmax)
kmax = kzmax;
if (kmin > kmax)
return false;
distance_to_box = kmin;
return true;
}
#endif
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