void Triangle(Vector3 t0, Vector3 t1, Vector3 t2, TGAImage image, TGAColor color, int[] zbuffer)
{
if (t0.Y == t1.Y && t0.Y == t2.Y)
{
return; // i dont care about degenerate triangles
}
if (t0.Y > t1.Y)
{
Swap(ref t0, ref t1);
}
if (t0.Y > t2.Y)
{
Swap(ref t0, ref t2);
}
if (t1.Y > t2.Y)
{
Swap(ref t1, ref t2);
}
int total_height = (int)(t2.Y - t0.Y);
for (int i = 0; i < total_height; i++)
{
bool second_half = i > t1.Y - t0.Y || t1.Y == t0.Y;
int segment_height = (int)(second_half ? t2.Y - t1.Y : t1.Y - t0.Y);
float alpha = (float)i / total_height;
float beta = (float)(i - (second_half ? t1.Y - t0.Y : 0)) / segment_height; // be careful: with above conditions no division by zero here
Vector3 A = t0 + (t2 - t0) * alpha;
Vector3 B = second_half ? t1 + (t2 - t1) * beta : t0 + (t1 - t0) * beta;
if (A.X > B.X)
{
Swap(ref A, ref B);
}
for (int j = (int)A.X; j <= B.X; j++)
{
float phi = B.X == A.X ? 1.0f : (float)(j - A.X) / (float)(B.X - A.X);
Vector3 P = A + (B - A) * phi;
P.X = j; P.Y = t0.Y + i; // a hack to fill holes (due to int cast precision problems)
int idx = (int)(j + (t0.Y + i) * width);
if (zbuffer[idx] < P.Z)
{
zbuffer[idx] = (int)P.Z;
image[(int)P.X, (int)P.Y] = color; // attention, due to int casts t0.Y+i != A.Y
}
}
}
}
public void Run()
{
var image = new TGAImage(width, height, Format.BGR);
var model = new Model("Resources/african_head.obj");
var zbuffer = Enumerable.Repeat(int.MinValue, width * height).ToArray();
Vector3 light_dir = new Vector3(0, 0, -1);
var sw = Stopwatch.StartNew();
//Triangle(pts, image, new TGAColor(255, 0, 0));
for (int i = 0; i < model.Faces.Count; i++)
{
var face = model.Faces[i];
Vector3[] screen_coords = new Vector3[3];
Vector3[] world_coords = new Vector3[3];
for (int j = 0; j < 3; j++)
{
Vector3 v = model.Vertices[face[j]];
screen_coords[j] = new Vector3((v.X + 1.0f) * width / 2.0f, (v.Y + 1.0f) * height / 2.0f, (v.Z + 1.0f) * depth / 2.0f);
world_coords[j] = v;
}
Vector3 n = Vector3.Cross((world_coords[2] - world_coords[0]), (world_coords[1] - world_coords[0])).Normalize();
float intensity = Vector3.Dot(n, light_dir);
if (intensity > 0)
{
Triangle(screen_coords[0], screen_coords[1], screen_coords[2], image, new TGAColor((byte)(intensity * 255), (byte)(intensity * 255), (byte)(intensity * 255), 255), zbuffer);
}
}
TGAImage zbimage = new TGAImage(width, height, Format.Grayscale);
for (int i = 0; i < width; i++)
{
for (int j = 0; j < height; j++)
{
zbimage[i, j] = new TGAColor(zbuffer[i + j * width], Format.Grayscale);
}
}
sw.Stop();
zbimage.VerticalFlip(); // i want to have the origin at the left bottom corner of the image
zbimage.WriteToFile("zbuffer.tga");
Console.WriteLine(sw.Elapsed);
image.VerticalFlip(); // i want to have the origin at the left bottom corner of the image
image.WriteToFile("output.tga");
}
private void Line(int x0, int y0, int x1, int y1, TGAImage image, TGAColor color)
{
var steep = false;
if (MathF.Abs(x0 - x1) < MathF.Abs(y0 - y1))
{
(x0, y0) = (y0, x0);
(x1, y1) = (y1, x1);
steep = true;
}
if (x0 > x1)
{
(x0, x1) = (x1, x0);
(y0, y1) = (y1, y0);
}
var dx = x1 - x0;
var dy = y1 - y0;
var derror2 = Math.Abs(dy) * 2;
var error2 = 0;
var y = y0;
for (var x = x0; x <= x1; x++)
{
if (steep)
{
image[y, x] = color;
}
else
{
image[x, y] = color;
}
error2 += derror2;
if (error2 > dx)
{
y += y1 > y0 ? 1 : -1;
error2 -= dx * 2;
}
}
}
void Triangle(Vector3[] pts, float[] zbuffer, TGAImage image, TGAColor color)
{
var bboxmin = new Vector2(float.MaxValue, float.MaxValue);
var bboxmax = new Vector2(float.MinValue, float.MinValue);
var clamp = new Vertex2(image.Width - 1, image.Height - 1);
for (var i = 0; i < 3; i++)
{
bboxmin.X = Math.Max(0, Math.Min(bboxmin.X, pts[i].X));
bboxmax.X = Math.Min(clamp.X, Math.Max(bboxmax.X, pts[i].X));
bboxmin.Y = Math.Max(0, Math.Min(bboxmin.Y, pts[i].Y));
bboxmax.Y = Math.Min(clamp.Y, Math.Max(bboxmax.Y, pts[i].Y));
}
Vector3 P = default;
for (P.X = bboxmin.X; P.X <= bboxmax.X; P.X++)
{
for (P.Y = bboxmin.Y; P.Y <= bboxmax.Y; P.Y++)
{
Vector3 bc_screen = Barycentric(pts[0], pts[1], pts[2], P);
if (bc_screen.X < 0 || bc_screen.Y < 0 || bc_screen.Z < 0)
{
continue;
}
P.Z = 0;
P.Z += pts[0].Y * bc_screen.X;
P.Z += pts[1].Y * bc_screen.Y;
P.Z += pts[2].Y * bc_screen.Z;
if (zbuffer[(int)(P.X + P.Y * width)] < P.Z)
{
zbuffer[(int)(P.X + P.Y * width)] = P.Z;
image[(int)P.X, (int)P.Y] = color;
}
}
}
}