void ProcessScanLine(ScanLineData data, Vertex va, Vertex vb, Vertex vc, Vertex vd, Color color)
{
Vector3 pa = va.Coordinates;
Vector3 pb = vb.Coordinates;
Vector3 pc = vc.Coordinates;
Vector3 pd = vd.Coordinates;
var gradient1 = pa.Y != pb.Y ? (data.currentY - pa.Y) / (pb.Y - pa.Y) : 1;
var gradient2 = pc.Y != pd.Y ? (data.currentY - pc.Y) / (pd.Y - pc.Y) : 1;
int sx = (int)Utils.Interpolate(pa.X, pb.X, gradient1);
int ex = (int)Utils.Interpolate(pc.X, pd.X, gradient2);
float z1 = Utils.Interpolate(pa.Z, pb.Z, gradient1);
float z2 = Utils.Interpolate(pc.Z, pd.Z, gradient2);
for (var x = sx; x < ex; x++)
{
float gradient = (x - sx) / (float)(ex - sx);
var z = Utils.Interpolate(z1, z2, gradient);
var ndotl = data.ndotla;
var newColor = Color.FromArgb((int)(color.R * ndotl), (int)(color.G * ndotl), (int)(color.B * ndotl));
DrawPoint(new Vector3(x, data.currentY, z), newColor);
}
}
public void DrawTriangle(Vertex v1, Vertex v2, Vertex v3, Color color)
{
if (v1.Coordinates.Y > v2.Coordinates.Y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
if (v2.Coordinates.Y > v3.Coordinates.Y)
{
var temp = v2;
v2 = v3;
v3 = temp;
}
if (v1.Coordinates.Y > v2.Coordinates.Y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
Vector3 p1 = v1.Coordinates;
Vector3 p2 = v2.Coordinates;
Vector3 p3 = v3.Coordinates;
Vector3 vnFace = (v1.Normal + v2.Normal + v3.Normal) / 3;
Vector3 centerPoint = (v1.WorldCoordinates + v2.WorldCoordinates + v3.WorldCoordinates) / 3;
Vector3 lightPos = new Vector3(-2, 0, 0);
float ndotl = Utils.ComputeNDotL(centerPoint, vnFace, lightPos);
var data = new ScanLineData {
ndotla = ndotl
};
float dP1P2, dP1P3;
if (p2.Y - p1.Y > 0)
{
dP1P2 = (p2.X - p1.X) / (p2.Y - p1.Y);
}
else
{
dP1P2 = 0;
}
if (p3.Y - p1.Y > 0)
{
dP1P3 = (p3.X - p1.X) / (p3.Y - p1.Y);
}
else
{
dP1P3 = 0;
}
if (dP1P2 > dP1P3)
{
for (var y = (int)p1.Y; y <= (int)p3.Y; y++)
{
data.currentY = y;
if (y < p2.Y)
{
ProcessScanLine(data, v1, v3, v1, v2, color);
}
else
{
ProcessScanLine(data, v1, v3, v2, v3, color);
}
}
}
else
{
for (var y = (int)p1.Y; y <= (int)p3.Y; y++)
{
data.currentY = y;
if (y < p2.Y)
{
ProcessScanLine(data, v1, v2, v1, v3, color);
}
else
{
ProcessScanLine(data, v2, v3, v1, v3, color);
}
}
}
}
