Edges on polygon outlines not always correct
- by user146780
I'm using the algorithm below to generate quads which are then rendered to make an outline like this
http://img810.imageshack.us/img810/8530/uhohz.png
The problem as seen on the image, is that sometimes the lines are too thin when they should always be the same width. My algorithm finds the 4 verticies for the first one then the top 2 verticies of the next ones are the bottom 2 of the previous. This creates connected lines, but it seems to not always work. How could I fix this?
This is my algorithm:
void OGLENGINEFUNCTIONS::GenerateLinePoly(const std::vector<std::vector<GLdouble>> &input,
std::vector<GLfloat> &output, int width)
{
output.clear();
if(input.size() < 2)
{
return;
}
int temp;
float dirlen;
float perplen;
POINTFLOAT start;
POINTFLOAT end;
POINTFLOAT dir;
POINTFLOAT ndir;
POINTFLOAT perp;
POINTFLOAT nperp;
POINTFLOAT perpoffset;
POINTFLOAT diroffset;
POINTFLOAT p0, p1, p2, p3;
for(unsigned int i = 0; i < input.size() - 1; ++i)
{
start.x = static_cast<float>(input[i][0]);
start.y = static_cast<float>(input[i][1]);
end.x = static_cast<float>(input[i + 1][0]);
end.y = static_cast<float>(input[i + 1][1]);
dir.x = end.x - start.x;
dir.y = end.y - start.y;
dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y));
ndir.x = static_cast<float>(dir.x * 1.0 / dirlen);
ndir.y = static_cast<float>(dir.y * 1.0 / dirlen);
perp.x = dir.y;
perp.y = -dir.x;
perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y));
nperp.x = static_cast<float>(perp.x * 1.0 / perplen);
nperp.y = static_cast<float>(perp.y * 1.0 / perplen);
perpoffset.x = static_cast<float>(nperp.x * width * 0.5);
perpoffset.y = static_cast<float>(nperp.y * width * 0.5);
diroffset.x = static_cast<float>(ndir.x * 0 * 0.5);
diroffset.y = static_cast<float>(ndir.y * 0 * 0.5);
// p0 = start + perpoffset - diroffset
//p1 = start - perpoffset - diroffset
//p2 = end + perpoffset + diroffset
// p3 = end - perpoffset + diroffset
p0.x = start.x + perpoffset.x - diroffset.x;
p0.y = start.y + perpoffset.y - diroffset.y;
p1.x = start.x - perpoffset.x - diroffset.x;
p1.y = start.y - perpoffset.y - diroffset.y;
if(i > 0)
{
temp = (8 * (i - 1));
p2.x = output[temp + 2];
p2.y = output[temp + 3];
p3.x = output[temp + 4];
p3.y = output[temp + 5];
}
else
{
p2.x = end.x + perpoffset.x + diroffset.x;
p2.y = end.y + perpoffset.y + diroffset.y;
p3.x = end.x - perpoffset.x + diroffset.x;
p3.y = end.y - perpoffset.y + diroffset.y;
}
output.push_back(p2.x);
output.push_back(p2.y);
output.push_back(p0.x);
output.push_back(p0.y);
output.push_back(p1.x);
output.push_back(p1.y);
output.push_back(p3.x);
output.push_back(p3.y);
}
}
Thanks
