public void DrawTriangle(Vertex v1, Vertex v2, Vertex v3, Color4 color)
{
// 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;
}
Vector3 p1 = v1.Coordinates;
Vector3 p2 = v2.Coordinates;
Vector3 p3 = v3.Coordinates;
// Light position
Vector3 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
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 { };
// computing lines' directions
float dP1P2, dP1P3;
// http://en.wikipedia.org/wiki/Slope
// 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;
ProcessScanLine(data, v1, v3, v1, v2, color);
}
else
{
data.ndotla = nl1;
data.ndotlb = nl3;
data.ndotlc = nl2;
data.ndotld = nl3;
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;
ProcessScanLine(data, v1, v2, v1, v3, color);
}
else
{
data.ndotla = nl2;
data.ndotlb = nl3;
data.ndotlc = nl1;
data.ndotld = nl3;
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;
// 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;
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);
var snl = Interpolate(data.ndotla, data.ndotlb, gradient1);
var enl = Interpolate(data.ndotlc, data.ndotld, gradient2);
// drawing a line from left (sx) to right (ex)
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);
// 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);
}
}
// Project takes some 3D coordinates and transform them
// in 2D coordinates using the transformation matrix
// It also transform the same coordinates and the norma to the vertex
// in the 3D world
public Vertex Project(Vertex vertex, Matrix transMat, Matrix world)
{
// transforming the coordinates into 2D space
var point2d = Vector3.TransformCoordinate(vertex.Coordinates, transMat);
// transforming the coordinates & the normal to the vertex in the 3D world
var point3dWorld = Vector3.TransformCoordinate(vertex.Coordinates, world);
var normal3dWorld = Vector3.TransformCoordinate(vertex.Normal, world);
// The transformed coordinates will be based on coordinate system
// starting on the center of the screen. But drawing on screen normally starts
// from top left. We then need to transform them again to have x:0, y:0 on top left.
var x = point2d.X * renderWidth + renderWidth / 2.0f;
var y = -point2d.Y * renderHeight + renderHeight / 2.0f;
return new Vertex
{
Coordinates = new Vector3(x, y, point2d.Z),
Normal = normal3dWorld,
WorldCoordinates = point3dWorld
};
}
public Mesh(string name, int verticesCount, int facesCount)
{
Vertices = new Vertex[verticesCount];
Faces = new Face[facesCount];
Name = name;
}
public static Mesh LoadOBJ(string objFile)
{
StreamReader reader = new StreamReader(File.OpenRead(objFile));
List <Vector3> vertices = new List <Vector3>();
List <Vector3> normals = new List <Vector3>();
List <Vector2> uvs = new List <Vector2>();
List <Tuple <int, int, int>[]> faces = new List <Tuple <int, int, int>[]>();
while (!reader.EndOfStream)
{
string line = reader.ReadLine();
string[] tokens = line.Split(' ').Skip(1).SkipWhile(t => t == string.Empty).ToArray();
if (line.StartsWith("#"))
{
continue;
}
else if (line.StartsWith("vn"))
{
float x = float.Parse(tokens[0]);
float y = float.Parse(tokens[1]);
float z = float.Parse(tokens[2]);
normals.Add(new Vector3(x, y, z));
}
else if (line.StartsWith("vt"))
{
float x = float.Parse(tokens[0]);
float y = float.Parse(tokens[1]);
uvs.Add(new Vector2(x, y));
}
else if (line.StartsWith("v"))
{
float x = float.Parse(tokens[0]);
float y = float.Parse(tokens[1]);
float z = float.Parse(tokens[2]);
vertices.Add(new Vector3(x, y, z));
}
else if (line.StartsWith("f"))
{
Tuple <int, int, int> v1 = ParseIndicies(tokens[0]);
Tuple <int, int, int> v2 = ParseIndicies(tokens[1]);
Tuple <int, int, int> v3 = ParseIndicies(tokens[2]);
faces.Add(new Tuple <int, int, int>[3] {
v1, v2, v3
});
if (tokens.Length > 3)
{
Tuple <int, int, int> v4 = ParseIndicies(tokens[3]);
faces.Add(new Tuple <int, int, int>[3] {
v1, v3, v4
});
}
}
}
List <Vertex> modelVerts = new List <Vertex>();
List <Face> modelFaces = new List <Face>();
for (int i = 0; i < faces.Count; i++)
{
Vertex[] faceVerts = new Vertex[3];
for (int j = 0; j < 3; j++)
{
int vertIdx = faces[i][j].Item1;
int uvIdx = faces[i][j].Item2;
int normIdx = faces[i][j].Item3;
faceVerts[j] = new Vertex
{
Coordinates = vertices[vertIdx],
Normal = (normIdx == -1) ? Vector3.Zero : normals[normIdx],
TextureCoordinates = (uvIdx == -1) ? Vector2.Zero : uvs[uvIdx]
};
}
modelVerts.AddRange(faceVerts);
modelFaces.Add(new Face
{
A = i * 3 + 0,
B = i * 3 + 1,
C = i * 3 + 2
});
}
Mesh mesh = new Mesh("objMesh", modelVerts.Count, modelFaces.Count);
modelVerts.CopyTo(mesh.Vertices);
modelFaces.CopyTo(mesh.Faces);
mesh.ComputeFacesNormals();
return(mesh);
}
public Mesh(string name, int verticesCount, int facesCount)
{
Vertices = new Vertex[verticesCount];
Faces = new Face[facesCount];
Name = name;
}