## contain (`lygia`/`geometry`/`triangle`/`contain`)

Does the position lie within the triangle

Dependencies:

Use:

``````<vec3> contain(<Triangle> tri, <vec3> _pos)
``````

Check it on Github

``````

#ifndef FNC_TRIANGLE_CONTAIN
#define FNC_TRIANGLE_CONTAIN

bool contain(Triangle _tri, vec3 _pos) {
// Move the triangle so that the point becomes the
// triangles origin
vec3 local_a = _tri.a - _pos;
vec3 local_b = _tri.b - _pos;
vec3 local_c = _tri.c - _pos;

// The point should be moved too, so they are both
// relative, but because we don't use p in the
// equation anymore, we don't need it!
// p -= p;

// Compute the normal vectors for triangles:
// u = normal of PBC
// v = normal of PCA
// w = normal of PAB

vec3 u = cross(local_b, local_c);
vec3 v = cross(local_c, local_a);
vec3 w = cross(local_a, local_b);

// Test to see if the normals are facing the same direction.
// If yes, the point is inside, otherwise it isn't.
return dot(u, v) >= 0.0 && dot(u, w) >= 0.0;
}

#endif
``````

Dependencies:

Use:

``````<float3> contain(<Triangle> tri, <float3> _pos)
``````

Check it on Github

``````

#ifndef FNC_TRIANGLE_CONTAIN
#define FNC_TRIANGLE_CONTAIN

bool contain(Triangle _tri, float3 _pos) {
// Move the triangle so that the point becomes the
// triangles origin
float3 local_a = _tri.a - _pos;
float3 local_b = _tri.b - _pos;
float3 local_c = _tri.c - _pos;

// The point should be moved too, so they are both
// relative, but because we don't use p in the
// equation anymore, we don't need it!
// p -= p;

// Compute the normal vectors for triangles:
// u = normal of PBC
// v = normal of PCA
// w = normal of PAB

float3 u = cross(local_b, local_c);
float3 v = cross(local_c, local_a);
float3 w = cross(local_a, local_b);

// Test to see if the normals are facing the same direction.
// If yes, the point is inside, otherwise it isn't.
return dot(u, v) >= 0.0f && dot(u, w) >= 0.0f;
}

#endif
``````

Dependencies:

Use:

``````<float3> contain(<Triangle> tri, <float3> _pos)
``````

Check it on Github

``````

#ifndef FNC_TRIANGLE_CONTAIN
#define FNC_TRIANGLE_CONTAIN

inline __host__ __device__ bool contain(const Triangle& _tri, const float3& _pos) {
// Move the triangle so that the point becomes the
// triangles origin
float3 local_a = _tri.a - _pos;
float3 local_b = _tri.b - _pos;
float3 local_c = _tri.c - _pos;

// The point should be moved too, so they are both
// relative, but because we don't use p in the
// equation anymore, we don't need it!
// p -= p;

// Compute the normal vectors for triangles:
// u = normal of PBC
// v = normal of PCA
// w = normal of PAB

float3 u = cross(local_b, local_c);
float3 v = cross(local_c, local_a);
float3 w = cross(local_a, local_b);

// Test to see if the normals are facing the same direction.
// If yes, the point is inside, otherwise it isn't.
return dot(u, v) >= 0.0f && dot(u, w) >= 0.0f;
}

#endif
``````