// public void DrawLine(Vector2 point0, Vector2 point1)
// {
// var dist = (point1 - point0).Length();
//
// // If the distance between the 2 points is less than 2 pixels
// // We're exiting
// if (dist < 2)
// return;
//
// // Find the middle point between first & second point
// Vector2 middlePoint = point0 + (point1 - point0)/2;
// // We draw this point on screen
// DrawPoint(middlePoint);
// // Recursive algorithm launched between first & middle point
// // and between middle & second point
// DrawLine(point0, middlePoint);
// DrawLine(middlePoint, point1);
// }
// public void DrawBLine(Vector2 point0, Vector2 point1)
// {
// var x0 = (int)point0.X;
// var y0 = (int)point0.Y;
// var x1 = (int)point1.X;
// var y1 = (int)point1.Y;
//
// var dx = Math.Abs(x1 - x0);
// var dy = Math.Abs(y1 - y0);
// var sx = (x0 < x1) ? 1 : -1;
// var sy = (y0 < y1) ? 1 : -1;
// var err = dx - dy;
//
// while (true) {
// DrawPoint(new Vector2(x0, y0));
//
// if ((x0 == x1) && (y0 == y1))
// break;
// var e2 = 2 * err;
// if (e2 > -dy) { err -= dy;
// x0 += sx;
// }
// if (e2 < dx) { err += dx;
// y0 += sy;
// }
// }
// }
// drawing line between 2 points from left to right
// papb -> pcpd
// pa, pb, pc, pd must then be sorted before
private void ProcessScanLine(ScanLineData data, Vertex va, Vertex vb, Vertex vc, Vertex vd, Color4 color, Texture texture)
{
var pa = va.Coordinates;
var pb = vb.Coordinates;
var pc = vc.Coordinates;
var pd = vd.Coordinates;
// Thanks to current Y, we can compute the gradient to compute others values like
// the starting X (sx) and ending X (ex) to draw between
// if pa.Y == pb.Y or pc.Y == pd.Y, gradient is forced to 1
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;
var sx = (int)Interpolate(pa.X, pb.X, gradient1);
var ex = (int)Interpolate(pc.X, pd.X, gradient2);
// starting Z & ending Z
var z1 = Interpolate(pa.Z, pb.Z, gradient1);
var 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);
// Interpolating texture coordinates on Y
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);
// drawing a line from left (sx) to right (ex)
for (var x = sx; x < ex; x++)
{
var gradient = (x - sx) / (float)(ex - sx);
// Interpolating Z, normal and texture coordinates on X
var z = Interpolate(z1, z2, gradient);
var ndotl = Interpolate(snl, enl, gradient);
// changing the color value using the cosine of the angle
// between the light vector and the normal vector
// DrawPoint(new Vector3(x, data.currentY, z), color * ndotl);
var u = Interpolate(su, eu, gradient);
var v = Interpolate(sv, ev, gradient);
var textureColor = texture?.Map(u, v) ?? new Color4(1, 1, 1, 1);
// changing the native color value using the cosine of the angle
// between the light vector and the normal vector
// and the texture color
DrawPoint(new Vector3(x, data.CurrentY, z), color * ndotl * textureColor);
}
}
private void DrawTriangle(Vertex v1, Vertex v2, Vertex v3, Color4 color, Texture texture)
{
// Sorting the points in order to always have this order on screen p1, p2 & p3
// with p1 always up (thus having the Y the lowest possible to be near the top screen)
// then p2 between p1 & p3
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;
}
var p1 = v1.Coordinates;
var p2 = v2.Coordinates;
var p3 = v3.Coordinates;
// Light position
var lightPos = new Vector3(0, 10, 10);
// computing the cos of the angle between the light vector and the normal vector
// it will return a value between 0 and 1 that will be used as the intensity of the color
var nl1 = ComputeNDotL(v1.WorldCoordinates, v1.Normal, lightPos);
var nl2 = ComputeNDotL(v2.WorldCoordinates, v2.Normal, lightPos);
var nl3 = ComputeNDotL(v3.WorldCoordinates, v3.Normal, lightPos);
var data = new ScanLineData();
// inverse slopes
float dP1P2, dP1P3;
// Computing inverse 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;
}
// First case where triangles are like that:
// P1
// -
// --
// - -
// - -
// - - P2
// - -
// - -
// -
// P3
if (dP1P2 > dP1P3)
{
// for (var y = (int)p1.Y; y <= (int)p3.Y; y++)
// {
// if (y < p2.Y)
// {
// ProcessScanLine(y, p1, p3, p1, p2, color);
// }
// else
// {
// ProcessScanLine(y, p1, p3, p2, p3, color);
// }
// }
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;
ProcessScanLine(data, v1, v3, v1, v2, color, texture);
}
else
{
data.Ndotla = nl1;
data.Ndotlb = nl3;
data.Ndotlc = nl2;
data.Ndotld = nl3;
ProcessScanLine(data, v1, v3, v2, v3, color, texture);
}
}
}
// First case where triangles are like that:
// P1
// -
// --
// - -
// - -
// P2 - -
// - -
// - -
// -
// P3
else
{
// for (var y = (int)p1.Y; y <= (int)p3.Y; y++)
// {
// if (y < p2.Y)
// {
// ProcessScanLine(y, p1, p2, p1, p3, color);
// }
// else
// {
// ProcessScanLine(y, p2, p3, p1, p3, color);
// }
// }
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;
ProcessScanLine(data, v1, v2, v1, v3, color, texture);
}
else
{
data.Ndotla = nl2;
data.Ndotlb = nl3;
data.Ndotlc = nl1;
data.Ndotld = nl3;
ProcessScanLine(data, v2, v3, v1, v3, color, texture);
}
}
}
//if (dP1P2 > dP1P3)
//{
// Parallel.For((int)p1.Y, (int)p3.Y + 1, y =>
// {
// if (y < p2.Y)
// {
// ProcessScanLine(y, p1, p3, p1, p2, color);
// }
// else
// {
// ProcessScanLine(y, p1, p3, p2, p3, color);
// }
// });
//}
//else
//{
// Parallel.For((int)p1.Y, (int)p3.Y + 1, y =>
// {
// if (y < p2.Y)
// {
// ProcessScanLine(y, p1, p2, p1, p3, color);
// }
// else
// {
// ProcessScanLine(y, p2, p3, p1, p3, color);
// }
// });
//}
}