unsigned int getPixel(GCamera& camera, int x, int y, double* pZ)
{
// Compute the ray vector
G3DVector ray;
camera.computeRayDirection(x, y, &ray);
// Compute the intersection with the billboard plane
double denom = m_face.dotProduct(&ray);
if(std::abs(denom) < 1e-12)
{
*pZ = -1e200;
return 0; // ray runs parallel to the plane
}
G3DVector t(m_pCorners[0]);
t.subtract(camera.lookFromPoint());
double d = m_face.dotProduct(&t) / denom;
*pZ = d;
if(d < 0)
return 0; // the intersection is behind the camera
ray.multiply(d);
ray.add(camera.lookFromPoint());
ray.subtract(m_pCorners[0]);
// Compute the image coordinates
int xx = (int)floor(ray.dotProduct(&m_bb.m_x) * m_pixelsX / m_squaredMagX + 0.5);
int yy = (int)floor(ray.dotProduct(&m_bb.m_y) * m_pixelsY / m_squaredMagY + 0.5);
// Get the pixel
if(xx < 0 || yy < 0 || xx >= m_pixelsX || yy >= m_pixelsY)
return 0;
return m_bb.m_pImage->pixel(xx % m_bb.m_pImage->width(), m_bb.m_pImage->height() - 1 - (yy % m_bb.m_pImage->height()));
}
void GBillboardWorld::draw(GImage* pImage, double* pDepthMap, GCamera& camera)
{
G3DVector coords[VERTEX_COUNT + 1];
int coordMap[VERTEX_COUNT + 1];
for(size_t i = 0; i < pImage->width() * pImage->height(); i++)
pDepthMap[i] = 1e200;
for(vector<GBillboard*>::iterator it = m_billboards.begin(); it != m_billboards.end(); it++)
{
// Project each of the corners onto the view
GBBAugmented bb(**it);
int gap = -1;
int coordCount = 0;
for(int i = 0; i < VERTEX_COUNT; i++)
{
camera.project(bb.m_pCorners[i], &coords[coordCount]);
if(coords[coordCount].m_vals[2] > 0.0)
coordMap[coordCount++] = i;
else if(gap < 0)
{
gap = coordCount;
coordCount = gap + 2;
}
}
// Fudge the gap due to vertices that are behind the camera
if(gap >= 0)
{
if(coordCount == 0)
continue; // Nothing to draw
// Fudge the vertex that follows the chain of valid vertices
G3DVector tmp;
G3DVector tmp2;
int indexValid = coordMap[(gap + coordCount - 1) % coordCount]; // The corner just before the gap
int indexFudge = (indexValid + 1) % VERTEX_COUNT; // The first corner that was behind the camera
tmp.copy(bb.m_pCorners[indexValid]);
tmp.subtract(bb.m_pCorners[indexFudge]);
tmp2.copy(camera.lookFromPoint());
tmp2.subtract(bb.m_pCorners[indexFudge]);
double d = (1e-6 + tmp2.dotProduct(camera.lookDirection())) / tmp.dotProduct(camera.lookDirection());
tmp.multiply(d);
tmp.add(bb.m_pCorners[indexFudge]);
camera.project(&tmp, &coords[gap]);
// Fudge the vertex that precedes the chain of valid vertices
indexValid = coordMap[(gap + 2) % coordCount]; // The corner just after the gap
indexFudge = (indexValid + VERTEX_COUNT - 1) % VERTEX_COUNT; // The last corner that was behind the camera
tmp.copy(bb.m_pCorners[indexValid]);
tmp.subtract(bb.m_pCorners[indexFudge]);
tmp2.copy(camera.lookFromPoint());
tmp2.subtract(bb.m_pCorners[indexFudge]);
d = (1e-6 + tmp2.dotProduct(camera.lookDirection())) / tmp.dotProduct(camera.lookDirection());
tmp.multiply(d);
tmp.add(bb.m_pCorners[indexFudge]);
camera.project(&tmp, &coords[gap + 1]);
}
// Find the starting point (which is the lowest coordinate in the view)
int a = 0;
for(int i = 1; i < coordCount; i++)
{
if(coords[i].m_vals[1] < coords[a].m_vals[1])
a = i;
}
int b = a;
// Find the left and right order in which the corners will be visted (bottom to top)
while(true)
{
int c = (b + 1) % coordCount;
if(a == c)
break;
int d = (a + coordCount - 1) % coordCount;
drawSection(pImage, pDepthMap, camera, bb, &coords[a], &coords[b], &coords[c], &coords[d]);
if(coords[d].m_vals[1] < coords[c].m_vals[1])
a = d;
else
b = c;
}
}
}
