void DrawPlane(const AABB& bounds, const Plane& plane)
{
Vec3 points[6];
struct Edge
{
int start;
int end;
};
static Edge edges[12] =
{
// bottom
{0, 1},
{1, 3},
{3, 2},
{2, 0},
// top
{4, 5},
{5, 7},
{7, 6},
{6, 4},
// top to bottom sides
{0, 4},
{1, 5},
{2, 6},
{3, 7},
};
// clip plane to bounds and render a quad
Vec3 corners[8];
const Vec3 *minmax[2] = { &bounds.m_min, &bounds.m_max };
for(int j = 0; j < 8; ++j)
{
int iz = j & 1;
int ix = (j >> 1) & 1;
int iy = (j >> 2) & 1;
corners[j] = Vec3(minmax[ix]->x, minmax[iy]->y, minmax[iz]->z);
}
int numPoints = 0;
// add corners
for(int j = 0; j < 8; ++j)
{
float planeDist = dot(plane.m_normal, corners[j]) - plane.m_d;
if(fabs(planeDist) < EPSILON)
points[numPoints++] = corners[j];
}
// add edges
for(int j = 0; j < 12; ++j)
{
Vec3 a = corners[edges[j].start];
Vec3 b = corners[edges[j].end];
Vec3 ab = b - a;
float t = (plane.m_d - dot(plane.m_normal, a)) / dot(plane.m_normal, ab);
if(t >= 0.f && t <= 1.f)
{
Vec3 pt = a + t * ab;
Vec3 ptA = a - pt;
Vec3 ptB = b - pt;
float distSqA = magnitude_squared(ptA);
float distSqB = magnitude_squared(ptB);
if(distSqA > EPSILON_SQ && distSqB > EPSILON_SQ)
{
points[numPoints++] = pt;
if(numPoints == 6)
break;
}
}
}
if(numPoints < 3)
return;
// Sort results
float inv_num = 1.f / numPoints;
Vec3 center(0,0,0);
for(int j = 0; j < numPoints; ++j)
center += points[j] * inv_num;
Vec3 sideVec = normalize(points[0] - center);
Vec3 upVec = normalize(cross(plane.m_normal, sideVec));
for(int j = 1; j < numPoints; ++j)
{
Vec3 toPointJ = points[j] - center;
float angleJ = AngleWrap(atan2(dot(upVec, toPointJ), dot(sideVec, toPointJ)));
for(int k = j+1; k < numPoints; ++k)
{
Vec3 toPointK = points[k] - center;
float angleK = AngleWrap(atan2(dot(upVec, toPointK), dot(sideVec, toPointK)));
if(angleK < angleJ)
{
angleJ = angleK;
Vec3 temp = points[j];
points[j] = points[k];
points[k] = temp;
}
}
}
// Draw outline
glColor3f(7.f, 0.3f, 0.3f);
glLineWidth(2.f);
glBegin(GL_LINES);
for(int j = 0; j < numPoints; ++j)
{
int next = (j + 1) % numPoints;
glVertex3fv(&points[j].x);
glVertex3fv(&points[next].x);
}
glEnd();
glLineWidth(1.f);
// Draw triangles
glColor4f(7.f, 0.3f, 0.3f, 0.3f);
glBegin(GL_TRIANGLE_FAN);
glVertex3fv(¢er.x);
for(int j = 0; j < numPoints; ++j)
glVertex3fv(&points[j].x);
glVertex3fv(&points[0].x);
glEnd();
glBegin(GL_TRIANGLE_FAN);
glVertex3fv(¢er.x);
for(int j = numPoints-1; j >= 0; --j)
glVertex3fv(&points[j].x);
glVertex3fv(&points[numPoints-1].x);
glEnd();
}
static void ddDrawPlane(const Plane& plane, const AABB& bounds, const Color& color)
{
vec3 points[6];
struct edge_t
{
int start;
int end;
};
static const edge_t edges[12] =
{
// bottom
{0, 1},
{1, 3},
{3, 2},
{2, 0},
// top
{4, 5},
{5, 7},
{7, 6},
{6, 4},
// top to bottom sides
{0, 4},
{1, 5},
{2, 6},
{3, 7},
};
// clip plane to bounds and render a quad
vec3 corners[8];
const vec3 *minmax[2] = { &bounds.m_min, &bounds.m_max };
for(int j = 0; j < 8; ++j)
{
int iz = j & 1;
int ix = (j >> 1) & 1;
int iy = (j >> 2) & 1;
corners[j].Set(minmax[ix]->x, minmax[iy]->y, minmax[iz]->z);
}
int numPoints = 0;
// add corners as points if they are close to the plane
for(int j = 0; j < 8; ++j)
{
float planeDist = PlaneDist(plane, corners[j]);
if(fabs(planeDist) < EPSILON)
points[numPoints++] = corners[j];
}
// add edge intersections
for(int j = 0; j < 12; ++j)
{
vec3 a = corners[edges[j].start],
b = corners[edges[j].end],
ab = b - a;
// intersect edge with plane
float t = (-plane.m_d - Dot(plane.m_n, a)) / Dot(plane.m_n, ab);
if(t >= 0.f && t <= 1.f)
{
vec3 pt = a + t * ab,
ptA = a - pt,
ptB = b - pt;
float distSqA = LengthSq(ptA);
float distSqB = LengthSq(ptB);
if(distSqA > EPSILON_SQ && distSqB > EPSILON_SQ)
{
points[numPoints++] = pt;
if(numPoints == 6)
break;
}
}
}
if(numPoints < 3)
return;
// Sort results
const float inv_num = 1.f / numPoints;
vec3 center = {0,0,0};
for(int j = 0; j < numPoints; ++j)
center += inv_num * points[j];
vec3 sideVec = Normalize(points[0] - center);
vec3 upVec = Normalize(Cross(plane.m_n, sideVec));
for(int j = 1; j < numPoints; ++j)
{
vec3 toPointJ = points[j] - center;
float angleJ = AngleWrap(atan2(Dot(upVec, toPointJ), Dot(sideVec, toPointJ)));
for(int k = j+1; k < numPoints; ++k)
{
vec3 toPointK = points[k] - center;
float angleK = AngleWrap(atan2(Dot(upVec, toPointK), Dot(sideVec, toPointK)));
if(angleK < angleJ)
{
angleJ = angleK;
std::swap(points[j], points[k]);
}
}
}
// Draw outline
const ShaderInfo* shader = g_dbgdrawShader.get();
GLint posLoc = shader->m_attrs[GEOM_Pos];
GLint colorLoc = shader->m_attrs[GEOM_Color];
glVertexAttrib3fv(colorLoc, &color.r);
glLineWidth(2.f);
glBegin(GL_LINES);
for(int j = 0; j < numPoints; ++j)
{
int next = (j + 1) % numPoints;
glVertexAttrib3fv(posLoc, &points[j].x);
glVertexAttrib3fv(posLoc, &points[next].x);
}
glEnd();
glLineWidth(1.f);
// Draw triangles
glVertexAttrib3fv(colorLoc, &color.r);
glBegin(GL_TRIANGLE_FAN);
glVertexAttrib3fv(posLoc, ¢er.x);
for(int j = 0; j < numPoints; ++j)
glVertexAttrib3fv(posLoc, &points[j].x);
glVertexAttrib3fv(posLoc, &points[0].x);
glEnd();
glBegin(GL_TRIANGLE_FAN);
glVertexAttrib3fv(posLoc, ¢er.x);
for(int j = numPoints-1; j >= 0; --j)
glVertexAttrib3fv(posLoc, &points[j].x);
glVertexAttrib3fv(posLoc, &points[numPoints-1].x);
glEnd();
}
