//--------------------------------------------------------------
// figure the normal for a point in grid
void Planet::pointNormal(
mgVertex& v,
double* heights,
mgPoint3* points,
int index,
int rowSize,
BOOL outward)
{
double ht = heights[index];
mgPoint3* npt = &points[index];
mgPoint3 pt(ht*npt->x, ht*npt->y, ht*npt->z);
v.m_px = (float) pt.x;
v.m_py = (float) pt.y;
v.m_pz = (float) pt.z;
ht = heights[index-rowSize];
npt = &points[index-rowSize];
mgPoint3 westPt(ht*npt->x, ht*npt->y, ht*npt->z);
ht = heights[index+rowSize];
npt = &points[index+rowSize];
mgPoint3 eastPt(ht*npt->x, ht*npt->y, ht*npt->z);
ht = heights[index-1];
npt = &points[index-1];
mgPoint3 northPt(ht*npt->x, ht*npt->y, ht*npt->z);
ht = heights[index+1];
npt = &points[index+1];
mgPoint3 southPt(ht*npt->x, ht*npt->y, ht*npt->z);
northPt.subtract(pt);
southPt.subtract(pt);
westPt.subtract(pt);
eastPt.subtract(pt);
mgPoint3 normal(northPt);
normal.cross(westPt);
normal.normalize();
v.m_nx = (float) normal.x;
v.m_ny = (float) normal.y;
v.m_nz = (float) normal.z;
normal = westPt;
normal.cross(southPt);
normal.normalize();
v.m_nx += (float) normal.x;
v.m_ny += (float) normal.y;
v.m_nz += (float) normal.z;
normal = southPt;
normal.cross(eastPt);
normal.normalize();
v.m_nx += (float) normal.x;
v.m_ny += (float) normal.y;
v.m_nz += (float) normal.z;
normal = eastPt;
normal.cross(northPt);
normal.normalize();
v.m_nx += (float) normal.x;
v.m_ny += (float) normal.y;
v.m_nz += (float) normal.z;
float len = sqrt(v.m_nx * v.m_nx + v.m_ny * v.m_ny + v.m_nz * v.m_nz);
if (!outward)
len = -len;
v.m_nx /= len;
v.m_ny /= len;
v.m_nz /= len;
}
//-----------------------------------------------------------------------------
// set normals of points on grid
void Wreck::setNormals(
mgVertexTA* points,
int rows,
int cols,
BOOL outward)
{
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
// get the point
int index = i*cols + j;
mgPoint3 pt(points[index].m_px, points[index].m_py, points[index].m_pz);
int northIndex = i*cols + ((j == cols-1) ? 1 : j+1);
mgPoint3 northPt(points[northIndex].m_px, points[northIndex].m_py, points[northIndex].m_pz);
northPt.subtract(pt);
int southIndex = i*cols + ((j == 0) ? cols-2 : j-1);
mgPoint3 southPt(points[southIndex].m_px, points[southIndex].m_py, points[southIndex].m_pz);
southPt.subtract(pt);
// normal is average of orthogonal vectors to each neighbor point
mgVertexTA* v = &points[index];
v->m_nx = v->m_ny = v->m_nz = 0.0f;
mgPoint3 normal;
if (i > 0)
{
int westIndex = (i-1)*cols + j;
mgPoint3 westPt(points[westIndex].m_px, points[westIndex].m_py, points[westIndex].m_pz);
westPt.subtract(pt);
normal = northPt;
normal.cross(westPt);
normal.normalize();
v->m_nx += (float) normal.x;
v->m_ny += (float) normal.y;
v->m_nz += (float) normal.z;
normal = westPt;
normal.cross(southPt);
normal.normalize();
v->m_nx += (float) normal.x;
v->m_ny += (float) normal.y;
v->m_nz += (float) normal.z;
}
if (i < rows-1)
{
// get vector to each neighbor point on grid
int eastIndex = (i+1)*cols + j;
mgPoint3 eastPt(points[eastIndex].m_px, points[eastIndex].m_py, points[eastIndex].m_pz);
eastPt.subtract(pt);
normal = southPt;
normal.cross(eastPt);
normal.normalize();
v->m_nx += (float) normal.x;
v->m_ny += (float) normal.y;
v->m_nz += (float) normal.z;
normal = eastPt;
normal.cross(northPt);
normal.normalize();
v->m_nx += (float) normal.x;
v->m_ny += (float) normal.y;
v->m_nz += (float) normal.z;
}
float len = sqrt(v->m_nx*v->m_nx + v->m_ny*v->m_ny + v->m_nz*v->m_nz);
if (outward)
len = -len;
v->m_nx /= len;
v->m_ny /= len;
v->m_nz /= len;
}
}
}
