public void DrawTriangle(Vertex v1, Vertex v2, Vertex v3, Color4 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;
// Light position
Vector3 lightPos = new Vector3(0, 10, 10);
float nl1 = ComputeNDotL(v1.WorldCoordinates, v1.Normal, lightPos);
float nl2 = ComputeNDotL(v2.WorldCoordinates, v2.Normal, lightPos);
float nl3 = ComputeNDotL(v3.WorldCoordinates, v3.Normal, lightPos);
var data = new ScanLineData { };
float dP1P2, dP1P3;
// Computing slopes
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)
{
data.ndotla = nl1;
data.ndotlb = nl3;
data.ndotlc = nl1;
data.ndotld = nl2;
data.ua = v1.TextureCoordinates.X;
data.ub = v3.TextureCoordinates.X;
data.uc = v1.TextureCoordinates.X;
data.ud = v2.TextureCoordinates.X;
data.va = v1.TextureCoordinates.Y;
data.vb = v3.TextureCoordinates.Y;
data.vc = v1.TextureCoordinates.Y;
data.vd = v2.TextureCoordinates.Y;
ProcessScanLine(data, v1, v3, v1, v2, color);
}
else
{
data.ndotla = nl1;
data.ndotlb = nl3;
data.ndotlc = nl2;
data.ndotld = nl3;
data.ua = v1.TextureCoordinates.X;
data.ub = v3.TextureCoordinates.X;
data.uc = v2.TextureCoordinates.X;
data.ud = v3.TextureCoordinates.X;
data.va = v1.TextureCoordinates.Y;
data.vb = v3.TextureCoordinates.Y;
data.vc = v2.TextureCoordinates.Y;
data.vd = v3.TextureCoordinates.Y;
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)
{
data.ndotla = nl1;
data.ndotlb = nl2;
data.ndotlc = nl1;
data.ndotld = nl3;
data.ua = v1.TextureCoordinates.X;
data.ub = v2.TextureCoordinates.X;
data.uc = v1.TextureCoordinates.X;
data.ud = v3.TextureCoordinates.X;
data.va = v1.TextureCoordinates.Y;
data.vb = v2.TextureCoordinates.Y;
data.vc = v1.TextureCoordinates.Y;
data.vd = v3.TextureCoordinates.Y;
ProcessScanLine(data, v1, v2, v1, v3, color);
}
else
{
data.ndotla = nl2;
data.ndotlb = nl3;
data.ndotlc = nl1;
data.ndotld = nl3;
data.ua = v2.TextureCoordinates.X;
data.ub = v3.TextureCoordinates.X;
data.uc = v1.TextureCoordinates.X;
data.ud = v3.TextureCoordinates.X;
data.va = v2.TextureCoordinates.Y;
data.vb = v3.TextureCoordinates.Y;
data.vc = v1.TextureCoordinates.Y;
data.vd = v3.TextureCoordinates.Y;
ProcessScanLine(data, v2, v3, v1, v3, color);
}
}
}
}
// drawing line between 2 points from left to right
// papb -> pcpd
// pa, pb, pc, pd must then be sorted before
void ProcessScanLine(ScanLineData data, Vertex va, Vertex vb, Vertex vc, Vertex vd, Color4 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)Interpolate(pa.X, pb.X, gradient1);
int ex = (int)Interpolate(pc.X, pd.X, gradient2);
// starting Z & ending Z
float z1 = Interpolate(pa.Z, pb.Z, gradient1);
float z2 = Interpolate(pc.Z, pd.Z, gradient2);
// Interpolating normals on Y
var snl = Interpolate(data.ndotla, data.ndotlb, gradient1);
var enl = Interpolate(data.ndotlc, data.ndotld, gradient2);
var su = Interpolate(data.ua, data.ub, gradient1);
var eu = Interpolate(data.uc, data.ud, gradient2);
var sv = Interpolate(data.va, data.vb, gradient1);
var ev = Interpolate(data.vc, data.vd, gradient2);
for (var x = sx; x < ex; x++)
{
float gradient = (x - sx) / (float)(ex - sx);
var z = Interpolate(z1, z2, gradient);
var ndotl = Interpolate(snl, enl, gradient);
var u = Interpolate(su, eu, gradient);
var v = Interpolate(sv, ev, gradient);
Color4 textureColor;
textureColor = new Color4(1, 1, 1, 1);
DrawPoint(new Vector3(x, data.currentY, z), color * ndotl);
}
}