public void FillTriangle(Vertex v1, Vertex v2, Vertex v3)
{
Matrix4f screenSpaceTransform =
new Matrix4f().InitScreenSpaceTransform(backBuffer.Width/2, backBuffer.Height/2);
Vertex minYVert = v1.Transform(screenSpaceTransform).PerspectiveDivide();
Vertex midYVert = v2.Transform(screenSpaceTransform).PerspectiveDivide();
Vertex maxYVert = v3.Transform(screenSpaceTransform).PerspectiveDivide();
if(maxYVert.GetY() < midYVert.GetY())
{
Vertex temp = maxYVert;
maxYVert = midYVert;
midYVert = temp;
}
if(midYVert.GetY() < minYVert.GetY())
{
Vertex temp = midYVert;
midYVert = minYVert;
minYVert = temp;
}
if(maxYVert.GetY() < midYVert.GetY())
{
Vertex temp = maxYVert;
maxYVert = midYVert;
midYVert = temp;
}
float area = minYVert.TriangleAreaTimes2(maxYVert, midYVert);
int handedness = area >= 0 ? 1 : 0;
ScanConvertTriangle(minYVert, midYVert, maxYVert, handedness);
FillShape((int)minYVert.GetY(), (int)maxYVert.GetY());
}
public float TriangleAreaTimes2(Vertex b, Vertex c)
{
float x1 = b.GetX() - m_pos.GetX();
float y1 = b.GetY() - m_pos.GetY();
float x2 = c.GetX() - m_pos.GetX();
float y2 = c.GetY() - m_pos.GetY();
return (x1 * y2 - x2 * y1);
}
public void ScanConvertLine(Vertex minYVert, Vertex maxYVert, int whichSide)
{
int yStart = (int)minYVert.GetY();
int yEnd = (int)maxYVert.GetY();
int xStart = (int)minYVert.GetX();
int xEnd = (int)maxYVert.GetX();
int yDist = yEnd - yStart;
int xDist = xEnd - xStart;
if(yDist <= 0)
{
return;
}
float xStep = (float)xDist/(float)yDist;
float curX = (float)xStart;
for(int j = yStart; j < yEnd; j++)
{
m_scanBuffer[j * 2 + whichSide] = (int)curX;
curX += xStep;
}
}
public void ScanConvertTriangle(Vertex minYVert, Vertex midYVert, Vertex maxYVert, int handedness)
{
ScanConvertLine(minYVert, maxYVert, 0 + handedness);
ScanConvertLine(minYVert, midYVert, 1 - handedness);
ScanConvertLine(midYVert, maxYVert, 1 - handedness);
}
