public static void Main (string[] args)
{
Device.Init (1024, 576, "Software Renderer");
// initialize a camera with 60 degrees field of view
// the second argument is the position of the camera (left handed)
Camera camera = new Camera (60, new Vector3 (0, 0, -10));
// load the storm trooper texture
Texture stormTrooperTexture = new Texture("../../Assets/Stormtrooper.png");
// load the stormtrooper mesh, and apply the specified texture
Mesh stormTrooper = new Mesh ("../../Assets/Stormtrooper.obj", stormTrooperTexture);
// scale in half
stormTrooper.scale = new Vector3 (0.5f, 0.5f, 0.5f);
// place y at -1 to have better view of the storm tropper
stormTrooper.position = new Vector3 (0, -1, 0);
// start with a 0 rotation
stormTrooper.rotationEuler = new Vector3 (0, 0, 0);
float z = camera.position.z;
float y = stormTrooper.rotationEuler.y;
while (Device.Active) {
// red background (remember, colors are not normalized in device space)
Device.Clear (255, 0, 0);
// input management, we rotate the mesh with left and right, and we zoom in/out with up and down
if (Device.GetKey (KeyCode.Right))
y+=3;
if (Device.GetKey (KeyCode.Left))
y-=3;
if (Device.GetKey (KeyCode.Up))
z+=1;
if (Device.GetKey (KeyCode.Down))
z-=1;
// set z of the camera
camera.position = new Vector3 (0, 0, z);
// apply rotation to the model
stormTrooper.rotationEuler = new Vector3(0, y, 0);
// draw the model
stormTrooper.Draw (camera);
// update the screen
Device.Update ();
}
}
// apply perspective projection to vector using the specified camera
public static Vector3 Project (this Vector3 v, Camera camera)
{
Vector3 v3;
float angle = camera.fov / 2 * Deg2Rad;
// 1f/tan(alpha)
float distanceFromCamera = (float)Math.Tan (angle);
v3.y = v.y / (distanceFromCamera * v.z);
v3.x = v.x / (aspectRatio * distanceFromCamera * v.z);
// hold the original z value, as it will be used by z-buffering
v3.z = v.z;
return v3;
}
// draw a 3d triangle in a 2d space
public void Draw (Camera camera)
{
// transform local coordinates in world coordinates
// remember: scaling is vector multiplication, translation is vector addition
Vector3 aWorld = this.a.coordinates.Rotate(mesh.rotationEuler) * mesh.scale + mesh.position;
Vector3 bWorld = this.b.coordinates.Rotate(mesh.rotationEuler) * mesh.scale + mesh.position;
Vector3 cWorld = this.c.coordinates.Rotate(mesh.rotationEuler) * mesh.scale + mesh.position;
// apply camera trasnformations (remember they are always inverted)
Vector3 aCamera = aWorld - (camera.position);
Vector3 bCamera = bWorld - (camera.position);
Vector3 cCamera = cWorld - (camera.position);
// project 3d vertices (in camera space) on 2d surface
this.a.projected = aCamera.Project (camera).NDCtoPixel ();
this.b.projected = bCamera.Project (camera).NDCtoPixel ();
this.c.projected = cCamera.Project (camera).NDCtoPixel ();
// now we have 2d triangles, time to rasterize them
// first step is ordering vertices from top to bottom
// order vertices (using projected coordinates [x and y are pixels, z is a copy of the camera transformation])
Vertex p1 = this.a;
Vertex p2 = this.b;
Vertex p3 = this.c;
// we use a dumb swapping algorithm for performances
if (p1.projected.y > p2.projected.y) {
var tmp = p2;
p2 = p1;
p1 = tmp;
}
if (p2.projected.y > p3.projected.y) {
var tmp = p2;
p2 = p3;
p3 = tmp;
}
if (p1.projected.y > p2.projected.y) {
var tmp = p2;
p2 = p1;
p1 = tmp;
}
// find slopes of the triangle edges, it is required to understand if P2 is on the left or on the right
float slopeP1P2 = (p2.projected.x - p1.projected.x) / (p2.projected.y - p1.projected.y);
float slopeP1P3 = (p3.projected.x - p1.projected.x) / (p3.projected.y - p1.projected.y);
// iterate y from p1 to p3
for (int y = (int)p1.projected.y; y <= (int)p3.projected.y; y++) {
// p2 on the left
if (slopeP1P3 > slopeP1P2) {
if (y < p2.projected.y) {
Device.ScanLine (y, p1, p2, p1, p3, mesh.texture);
} else {
Device.ScanLine (y, p2, p3, p1, p3, mesh.texture);
}
} else {
//p2 on the right
if (y < p2.projected.y) {
Device.ScanLine (y, p1, p3, p1, p2, mesh.texture);
} else {
Device.ScanLine (y, p1, p3, p2, p3, mesh.texture);
}
}
}
}
public void Draw (Camera camera)
{
foreach (Triangle face in this.faces) {
face.Draw (camera);
}
}
