OneLoneCoder_olcEngine3D_Part3.cpp

/*
OneLoneCoder.com - 3D Graphics Part #3 - Cameras & Clipping
"Tredimensjonal Grafikk" - @Javidx9

License
~~~~~~~
One Lone Coder Console Game Engine  Copyright (C) 2018  Javidx9
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; See license for details.
Original works located at:
https://www.github.com/onelonecoder
https://www.onelonecoder.com
https://www.youtube.com/javidx9
GNU GPLv3
https://github.com/OneLoneCoder/videos/blob/master/LICENSE

From Javidx9 :)
~~~~~~~~~~~~~~~
Hello! Ultimately I don't care what you use this for. It's intended to be
educational, and perhaps to the oddly minded - a little bit of fun.
Please hack this, change it and use it in any way you see fit. You acknowledge
that I am not responsible for anything bad that happens as a result of
your actions. However this code is protected by GNU GPLv3, see the license in the
github repo. This means you must attribute me if you use it. You can view this
license here: https://github.com/OneLoneCoder/videos/blob/master/LICENSE
Cheers!

Background
~~~~~~~~~~
3D Graphics is an interesting, visually pleasing suite of algorithms. This is the
first video in a series that will demonstrate the fundamentals required to 
build your own software based 3D graphics systems.

Video
~~~~~
https://youtu.be/ih20l3pJoeU
https://youtu.be/XgMWc6LumG4
https://youtu.be/HXSuNxpCzdM

Author
~~~~~~
Twitter: @javidx9
Blog: http://www.onelonecoder.com
Discord: https://discord.gg/WhwHUMV


Last Updated: 14/08/2018
*/


#include "olcConsoleGameEngine.h"
#include <fstream>
#include <strstream>
#include <algorithm>
using namespace std;


struct vec3d
{
	float x = 0;
	float y = 0;
	float z = 0;
	float w = 1; // Need a 4th term to perform sensible matrix vector multiplication
};

struct triangle
{
	vec3d p[3];
	wchar_t sym;
	short col;
};

struct mesh
{
	vector<triangle> tris;

	bool LoadFromObjectFile(string sFilename)
	{
		ifstream f(sFilename);
		if (!f.is_open())
			return false;

		// Local cache of verts
		vector<vec3d> verts;

		while (!f.eof())
		{
			char line[128];
			f.getline(line, 128);

			strstream s;
			s << line;

			char junk;

			if (line[0] == 'v')
			{
				vec3d v;
				s >> junk >> v.x >> v.y >> v.z;
				verts.push_back(v);
			}

			if (line[0] == 'f')
			{
				int f[3];
				s >> junk >> f[0] >> f[1] >> f[2];
				tris.push_back({ verts[f[0] - 1], verts[f[1] - 1], verts[f[2] - 1] });
			}
		}
		return true;
	}
};

struct mat4x4
{
	float m[4][4] = { 0 };
};

class olcEngine3D : public olcConsoleGameEngine
{
public:
	olcEngine3D()
	{
		m_sAppName = L"3D Demo";
	}


private:
	mesh meshCube;
	mat4x4 matProj;	// Matrix that converts from view space to screen space
	vec3d vCamera;	// Location of camera in world space
	vec3d vLookDir;	// Direction vector along the direction camera points
	float fYaw;		// FPS Camera rotation in XZ plane
	float fTheta;	// Spins World transform

	vec3d Matrix_MultiplyVector(mat4x4 &m, vec3d &i)
	{
		vec3d v;
		v.x = i.x * m.m[0][0] + i.y * m.m[1][0] + i.z * m.m[2][0] + i.w * m.m[3][0];
		v.y = i.x * m.m[0][1] + i.y * m.m[1][1] + i.z * m.m[2][1] + i.w * m.m[3][1];
		v.z = i.x * m.m[0][2] + i.y * m.m[1][2] + i.z * m.m[2][2] + i.w * m.m[3][2];
		v.w = i.x * m.m[0][3] + i.y * m.m[1][3] + i.z * m.m[2][3] + i.w * m.m[3][3];
		return v;
	}

	mat4x4 Matrix_MakeIdentity()
	{
		mat4x4 matrix;
		matrix.m[0][0] = 1.0f;
		matrix.m[1][1] = 1.0f;
		matrix.m[2][2] = 1.0f;
		matrix.m[3][3] = 1.0f;
		return matrix;
	}

	mat4x4 Matrix_MakeRotationX(float fAngleRad)
	{
		mat4x4 matrix;
		matrix.m[0][0] = 1.0f;
		matrix.m[1][1] = cosf(fAngleRad);
		matrix.m[1][2] = sinf(fAngleRad);
		matrix.m[2][1] = -sinf(fAngleRad);
		matrix.m[2][2] = cosf(fAngleRad);
		matrix.m[3][3] = 1.0f;
		return matrix;
	}

	mat4x4 Matrix_MakeRotationY(float fAngleRad)
	{
		mat4x4 matrix;
		matrix.m[0][0] = cosf(fAngleRad);
		matrix.m[0][2] = sinf(fAngleRad);
		matrix.m[2][0] = -sinf(fAngleRad);
		matrix.m[1][1] = 1.0f;
		matrix.m[2][2] = cosf(fAngleRad);
		matrix.m[3][3] = 1.0f;
		return matrix;
	}

	mat4x4 Matrix_MakeRotationZ(float fAngleRad)
	{
		mat4x4 matrix;
		matrix.m[0][0] = cosf(fAngleRad);
		matrix.m[0][1] = sinf(fAngleRad);
		matrix.m[1][0] = -sinf(fAngleRad);
		matrix.m[1][1] = cosf(fAngleRad);
		matrix.m[2][2] = 1.0f;
		matrix.m[3][3] = 1.0f;
		return matrix;
	}

	mat4x4 Matrix_MakeTranslation(float x, float y, float z)
	{
		mat4x4 matrix;
		matrix.m[0][0] = 1.0f;
		matrix.m[1][1] = 1.0f;
		matrix.m[2][2] = 1.0f;
		matrix.m[3][3] = 1.0f;
		matrix.m[3][0] = x;
		matrix.m[3][1] = y;
		matrix.m[3][2] = z;
		return matrix;
	}

	mat4x4 Matrix_MakeProjection(float fFovDegrees, float fAspectRatio, float fNear, float fFar)
	{
		float fFovRad = 1.0f / tanf(fFovDegrees * 0.5f / 180.0f * 3.14159f);
		mat4x4 matrix;
		matrix.m[0][0] = fAspectRatio * fFovRad;
		matrix.m[1][1] = fFovRad;
		matrix.m[2][2] = fFar / (fFar - fNear);
		matrix.m[3][2] = (-fFar * fNear) / (fFar - fNear);
		matrix.m[2][3] = 1.0f;
		matrix.m[3][3] = 0.0f;
		return matrix;
	}

	mat4x4 Matrix_MultiplyMatrix(mat4x4 &m1, mat4x4 &m2)
	{
		mat4x4 matrix;
		for (int c = 0; c < 4; c++)
			for (int r = 0; r < 4; r++)
				matrix.m[r][c] = m1.m[r][0] * m2.m[0][c] + m1.m[r][1] * m2.m[1][c] + m1.m[r][2] * m2.m[2][c] + m1.m[r][3] * m2.m[3][c];
		return matrix;
	}

	mat4x4 Matrix_PointAt(vec3d &pos, vec3d &target, vec3d &up)
	{
		// Calculate new forward direction
		vec3d newForward = Vector_Sub(target, pos);
		newForward = Vector_Normalise(newForward);

		// Calculate new Up direction
		vec3d a = Vector_Mul(newForward, Vector_DotProduct(up, newForward));
		vec3d newUp = Vector_Sub(up, a);
		newUp = Vector_Normalise(newUp);

		// New Right direction is easy, its just cross product
		vec3d newRight = Vector_CrossProduct(newUp, newForward);

		// Construct Dimensioning and Translation Matrix	
		mat4x4 matrix;
		matrix.m[0][0] = newRight.x;	matrix.m[0][1] = newRight.y;	matrix.m[0][2] = newRight.z;	matrix.m[0][3] = 0.0f;
		matrix.m[1][0] = newUp.x;		matrix.m[1][1] = newUp.y;		matrix.m[1][2] = newUp.z;		matrix.m[1][3] = 0.0f;
		matrix.m[2][0] = newForward.x;	matrix.m[2][1] = newForward.y;	matrix.m[2][2] = newForward.z;	matrix.m[2][3] = 0.0f;
		matrix.m[3][0] = pos.x;			matrix.m[3][1] = pos.y;			matrix.m[3][2] = pos.z;			matrix.m[3][3] = 1.0f;
		return matrix;

	}

	mat4x4 Matrix_QuickInverse(mat4x4 &m) // Only for Rotation/Translation Matrices
	{
		mat4x4 matrix;
		matrix.m[0][0] = m.m[0][0]; matrix.m[0][1] = m.m[1][0]; matrix.m[0][2] = m.m[2][0]; matrix.m[0][3] = 0.0f;
		matrix.m[1][0] = m.m[0][1]; matrix.m[1][1] = m.m[1][1]; matrix.m[1][2] = m.m[2][1]; matrix.m[1][3] = 0.0f;
		matrix.m[2][0] = m.m[0][2]; matrix.m[2][1] = m.m[1][2]; matrix.m[2][2] = m.m[2][2]; matrix.m[2][3] = 0.0f;
		matrix.m[3][0] = -(m.m[3][0] * matrix.m[0][0] + m.m[3][1] * matrix.m[1][0] + m.m[3][2] * matrix.m[2][0]);
		matrix.m[3][1] = -(m.m[3][0] * matrix.m[0][1] + m.m[3][1] * matrix.m[1][1] + m.m[3][2] * matrix.m[2][1]);
		matrix.m[3][2] = -(m.m[3][0] * matrix.m[0][2] + m.m[3][1] * matrix.m[1][2] + m.m[3][2] * matrix.m[2][2]);
		matrix.m[3][3] = 1.0f;
		return matrix;
	}

	vec3d Vector_Add(vec3d &v1, vec3d &v2)
	{
		return { v1.x + v2.x, v1.y + v2.y, v1.z + v2.z };
	}

	vec3d Vector_Sub(vec3d &v1, vec3d &v2)
	{
		return { v1.x - v2.x, v1.y - v2.y, v1.z - v2.z };
	}

	vec3d Vector_Mul(vec3d &v1, float k)
	{
		return { v1.x * k, v1.y * k, v1.z * k };
	}

	vec3d Vector_Div(vec3d &v1, float k)
	{
		return { v1.x / k, v1.y / k, v1.z / k };
	}

	float Vector_DotProduct(vec3d &v1, vec3d &v2)
	{
		return v1.x*v2.x + v1.y*v2.y + v1.z * v2.z;
	}

	float Vector_Length(vec3d &v)
	{
		return sqrtf(Vector_DotProduct(v, v));
	}

	vec3d Vector_Normalise(vec3d &v)
	{
		float l = Vector_Length(v);
		return { v.x / l, v.y / l, v.z / l };
	}

	vec3d Vector_CrossProduct(vec3d &v1, vec3d &v2)
	{
		vec3d v;
		v.x = v1.y * v2.z - v1.z * v2.y;
		v.y = v1.z * v2.x - v1.x * v2.z;
		v.z = v1.x * v2.y - v1.y * v2.x;
		return v;
	}

	vec3d Vector_IntersectPlane(vec3d &plane_p, vec3d &plane_n, vec3d &lineStart, vec3d &lineEnd)
	{
		plane_n = Vector_Normalise(plane_n);
		float plane_d = -Vector_DotProduct(plane_n, plane_p);
		float ad = Vector_DotProduct(lineStart, plane_n);
		float bd = Vector_DotProduct(lineEnd, plane_n);
		float t = (-plane_d - ad) / (bd - ad);
		vec3d lineStartToEnd = Vector_Sub(lineEnd, lineStart);
		vec3d lineToIntersect = Vector_Mul(lineStartToEnd, t);
		return Vector_Add(lineStart, lineToIntersect);
	}

	int Triangle_ClipAgainstPlane(vec3d plane_p, vec3d plane_n, triangle &in_tri, triangle &out_tri1, triangle &out_tri2)
	{
		// Make sure plane normal is indeed normal
		plane_n = Vector_Normalise(plane_n);

		// Return signed shortest distance from point to plane, plane normal must be normalised
		auto dist = [&](vec3d &p)
		{
			vec3d n = Vector_Normalise(p);
			return (plane_n.x * p.x + plane_n.y * p.y + plane_n.z * p.z - Vector_DotProduct(plane_n, plane_p));
		};

		// Create two temporary storage arrays to classify points either side of plane
		// If distance sign is positive, point lies on "inside" of plane
		vec3d* inside_points[3];  int nInsidePointCount = 0;
		vec3d* outside_points[3]; int nOutsidePointCount = 0;

		// Get signed distance of each point in triangle to plane
		float d0 = dist(in_tri.p[0]);
		float d1 = dist(in_tri.p[1]);
		float d2 = dist(in_tri.p[2]);

		if (d0 >= 0) { inside_points[nInsidePointCount++] = &in_tri.p[0]; }
		else { outside_points[nOutsidePointCount++] = &in_tri.p[0]; }
		if (d1 >= 0) { inside_points[nInsidePointCount++] = &in_tri.p[1]; }
		else { outside_points[nOutsidePointCount++] = &in_tri.p[1]; }
		if (d2 >= 0) { inside_points[nInsidePointCount++] = &in_tri.p[2]; }
		else { outside_points[nOutsidePointCount++] = &in_tri.p[2]; }

		// Now classify triangle points, and break the input triangle into 
		// smaller output triangles if required. There are four possible
		// outcomes...

		if (nInsidePointCount == 0)
		{
			// All points lie on the outside of plane, so clip whole triangle
			// It ceases to exist

			return 0; // No returned triangles are valid
		}

		if (nInsidePointCount == 3)
		{
			// All points lie on the inside of plane, so do nothing
			// and allow the triangle to simply pass through
			out_tri1 = in_tri;

			return 1; // Just the one returned original triangle is valid
		}

		if (nInsidePointCount == 1 && nOutsidePointCount == 2)
		{
			// Triangle should be clipped. As two points lie outside
			// the plane, the triangle simply becomes a smaller triangle

			// Copy appearance info to new triangle
			out_tri1.col =  in_tri.col;
			out_tri1.sym = in_tri.sym;

			// The inside point is valid, so keep that...
			out_tri1.p[0] = *inside_points[0];

			// but the two new points are at the locations where the 
			// original sides of the triangle (lines) intersect with the plane
			out_tri1.p[1] = Vector_IntersectPlane(plane_p, plane_n, *inside_points[0], *outside_points[0]);
			out_tri1.p[2] = Vector_IntersectPlane(plane_p, plane_n, *inside_points[0], *outside_points[1]);

			return 1; // Return the newly formed single triangle
		}

		if (nInsidePointCount == 2 && nOutsidePointCount == 1)
		{
			// Triangle should be clipped. As two points lie inside the plane,
			// the clipped triangle becomes a "quad". Fortunately, we can
			// represent a quad with two new triangles

			// Copy appearance info to new triangles
			out_tri1.col =  in_tri.col;
			out_tri1.sym = in_tri.sym;

			out_tri2.col =  in_tri.col;
			out_tri2.sym = in_tri.sym;

			// The first triangle consists of the two inside points and a new
			// point determined by the location where one side of the triangle
			// intersects with the plane
			out_tri1.p[0] = *inside_points[0];
			out_tri1.p[1] = *inside_points[1];
			out_tri1.p[2] = Vector_IntersectPlane(plane_p, plane_n, *inside_points[0], *outside_points[0]);

			// The second triangle is composed of one of he inside points, a
			// new point determined by the intersection of the other side of the 
			// triangle and the plane, and the newly created point above
			out_tri2.p[0] = *inside_points[1];
			out_tri2.p[1] = out_tri1.p[2];
			out_tri2.p[2] = Vector_IntersectPlane(plane_p, plane_n, *inside_points[1], *outside_points[0]);

			return 2; // Return two newly formed triangles which form a quad
		}
	}



	// Taken From Command Line Webcam Video
	CHAR_INFO GetColour(float lum)
	{
		short bg_col, fg_col;
		wchar_t sym;
		int pixel_bw = (int)(13.0f*lum);
		switch (pixel_bw)
		{
		case 0: bg_col = BG_BLACK; fg_col = FG_BLACK; sym = PIXEL_SOLID; break;

		case 1: bg_col = BG_BLACK; fg_col = FG_DARK_GREY; sym = PIXEL_QUARTER; break;
		case 2: bg_col = BG_BLACK; fg_col = FG_DARK_GREY; sym = PIXEL_HALF; break;
		case 3: bg_col = BG_BLACK; fg_col = FG_DARK_GREY; sym = PIXEL_THREEQUARTERS; break;
		case 4: bg_col = BG_BLACK; fg_col = FG_DARK_GREY; sym = PIXEL_SOLID; break;

		case 5: bg_col = BG_DARK_GREY; fg_col = FG_GREY; sym = PIXEL_QUARTER; break;
		case 6: bg_col = BG_DARK_GREY; fg_col = FG_GREY; sym = PIXEL_HALF; break;
		case 7: bg_col = BG_DARK_GREY; fg_col = FG_GREY; sym = PIXEL_THREEQUARTERS; break;
		case 8: bg_col = BG_DARK_GREY; fg_col = FG_GREY; sym = PIXEL_SOLID; break;

		case 9:  bg_col = BG_GREY; fg_col = FG_WHITE; sym = PIXEL_QUARTER; break;
		case 10: bg_col = BG_GREY; fg_col = FG_WHITE; sym = PIXEL_HALF; break;
		case 11: bg_col = BG_GREY; fg_col = FG_WHITE; sym = PIXEL_THREEQUARTERS; break;
		case 12: bg_col = BG_GREY; fg_col = FG_WHITE; sym = PIXEL_SOLID; break;
		default:
			bg_col = BG_BLACK; fg_col = FG_BLACK; sym = PIXEL_SOLID;
		}

		CHAR_INFO c;
		c.Attributes = bg_col | fg_col;
		c.Char.UnicodeChar = sym;
		return c;
	}

public:
	bool OnUserCreate() override
	{
		// Load object file
		meshCube.LoadFromObjectFile("mountains.obj");

		// Projection Matrix
		matProj = Matrix_MakeProjection(90.0f, (float)ScreenHeight() / (float)ScreenWidth(), 0.1f, 1000.0f);
		return true;
	}

	bool OnUserUpdate(float fElapsedTime) override
	{
		if (GetKey(VK_UP).bHeld)
			vCamera.y += 8.0f * fElapsedTime;	// Travel Upwards

		if (GetKey(VK_DOWN).bHeld)
			vCamera.y -= 8.0f * fElapsedTime;	// Travel Downwards


		// Dont use these two in FPS mode, it is confusing :P
		if (GetKey(VK_LEFT).bHeld)
			vCamera.x -= 8.0f * fElapsedTime;	// Travel Along X-Axis

		if (GetKey(VK_RIGHT).bHeld)
			vCamera.x += 8.0f * fElapsedTime;	// Travel Along X-Axis
		///////


		vec3d vForward = Vector_Mul(vLookDir, 8.0f * fElapsedTime);

		// Standard FPS Control scheme, but turn instead of strafe
		if (GetKey(L'W').bHeld)
			vCamera = Vector_Add(vCamera, vForward);

		if (GetKey(L'S').bHeld)
			vCamera = Vector_Sub(vCamera, vForward);

		if (GetKey(L'A').bHeld)
			fYaw -= 2.0f * fElapsedTime;

		if (GetKey(L'D').bHeld)
			fYaw += 2.0f * fElapsedTime;


		

		// Set up "World Tranmsform" though not updating theta 
		// makes this a bit redundant
		mat4x4 matRotZ, matRotX;
		//fTheta += 1.0f * fElapsedTime; // Uncomment to spin me right round baby right round
		matRotZ = Matrix_MakeRotationZ(fTheta * 0.5f);
		matRotX = Matrix_MakeRotationX(fTheta);

		mat4x4 matTrans;
		matTrans = Matrix_MakeTranslation(0.0f, 0.0f, 5.0f);

		mat4x4 matWorld;
		matWorld = Matrix_MakeIdentity();	// Form World Matrix
		matWorld = Matrix_MultiplyMatrix(matRotZ, matRotX); // Transform by rotation
		matWorld = Matrix_MultiplyMatrix(matWorld, matTrans); // Transform by translation

		// Create "Point At" Matrix for camera
		vec3d vUp = { 0,1,0 };
		vec3d vTarget = { 0,0,1 };
		mat4x4 matCameraRot = Matrix_MakeRotationY(fYaw);
		vLookDir = Matrix_MultiplyVector(matCameraRot, vTarget);
		vTarget = Vector_Add(vCamera, vLookDir);
		mat4x4 matCamera = Matrix_PointAt(vCamera, vTarget, vUp);

		// Make view matrix from camera
		mat4x4 matView = Matrix_QuickInverse(matCamera);

		// Store triagles for rastering later
		vector<triangle> vecTrianglesToRaster;

		// Draw Triangles
		for (auto tri : meshCube.tris)
		{
			triangle triProjected, triTransformed, triViewed;

			// World Matrix Transform
			triTransformed.p[0] = Matrix_MultiplyVector(matWorld, tri.p[0]);
			triTransformed.p[1] = Matrix_MultiplyVector(matWorld, tri.p[1]);
			triTransformed.p[2] = Matrix_MultiplyVector(matWorld, tri.p[2]);

			// Calculate triangle Normal
			vec3d normal, line1, line2;

			// Get lines either side of triangle
			line1 = Vector_Sub(triTransformed.p[1], triTransformed.p[0]);
			line2 = Vector_Sub(triTransformed.p[2], triTransformed.p[0]);

			// Take cross product of lines to get normal to triangle surface
			normal = Vector_CrossProduct(line1, line2);

			// You normally need to normalise a normal!
			normal = Vector_Normalise(normal);
			
			// Get Ray from triangle to camera
			vec3d vCameraRay = Vector_Sub(triTransformed.p[0], vCamera);

			// If ray is aligned with normal, then triangle is visible
			if (Vector_DotProduct(normal, vCameraRay) < 0.0f)
			{
				// Illumination
				vec3d light_direction = { 0.0f, 1.0f, -1.0f };
				light_direction = Vector_Normalise(light_direction);

				// How "aligned" are light direction and triangle surface normal?
				float dp = max(0.1f, Vector_DotProduct(light_direction, normal));

				// Choose console colours as required (much easier with RGB)
				CHAR_INFO c = GetColour(dp);
				triTransformed.col = c.Attributes;
				triTransformed.sym = c.Char.UnicodeChar;

				// Convert World Space --> View Space
				triViewed.p[0] = Matrix_MultiplyVector(matView, triTransformed.p[0]);
				triViewed.p[1] = Matrix_MultiplyVector(matView, triTransformed.p[1]);
				triViewed.p[2] = Matrix_MultiplyVector(matView, triTransformed.p[2]);
				triViewed.sym = triTransformed.sym;
				triViewed.col = triTransformed.col;

				// Clip Viewed Triangle against near plane, this could form two additional
				// additional triangles. 
				int nClippedTriangles = 0;
				triangle clipped[2];
				nClippedTriangles = Triangle_ClipAgainstPlane({ 0.0f, 0.0f, 0.1f }, { 0.0f, 0.0f, 1.0f }, triViewed, clipped[0], clipped[1]);

				// We may end up with multiple triangles form the clip, so project as
				// required
				for (int n = 0; n < nClippedTriangles; n++)
				{
					// Project triangles from 3D --> 2D
					triProjected.p[0] = Matrix_MultiplyVector(matProj, clipped[n].p[0]);
					triProjected.p[1] = Matrix_MultiplyVector(matProj, clipped[n].p[1]);
					triProjected.p[2] = Matrix_MultiplyVector(matProj, clipped[n].p[2]);
					triProjected.col = clipped[n].col;
					triProjected.sym = clipped[n].sym;

					// Scale into view, we moved the normalising into cartesian space
					// out of the matrix.vector function from the previous videos, so
					// do this manually
					triProjected.p[0] = Vector_Div(triProjected.p[0], triProjected.p[0].w);
					triProjected.p[1] = Vector_Div(triProjected.p[1], triProjected.p[1].w);
					triProjected.p[2] = Vector_Div(triProjected.p[2], triProjected.p[2].w);

					// X/Y are inverted so put them back
					triProjected.p[0].x *= -1.0f;
					triProjected.p[1].x *= -1.0f;
					triProjected.p[2].x *= -1.0f;
					triProjected.p[0].y *= -1.0f;
					triProjected.p[1].y *= -1.0f;
					triProjected.p[2].y *= -1.0f;

					// Offset verts into visible normalised space
					vec3d vOffsetView = { 1,1,0 };
					triProjected.p[0] = Vector_Add(triProjected.p[0], vOffsetView);
					triProjected.p[1] = Vector_Add(triProjected.p[1], vOffsetView);
					triProjected.p[2] = Vector_Add(triProjected.p[2], vOffsetView);
					triProjected.p[0].x *= 0.5f * (float)ScreenWidth();
					triProjected.p[0].y *= 0.5f * (float)ScreenHeight();
					triProjected.p[1].x *= 0.5f * (float)ScreenWidth();
					triProjected.p[1].y *= 0.5f * (float)ScreenHeight();
					triProjected.p[2].x *= 0.5f * (float)ScreenWidth();
					triProjected.p[2].y *= 0.5f * (float)ScreenHeight();

					// Store triangle for sorting
					vecTrianglesToRaster.push_back(triProjected);
				}			
			}
		}

		// Sort triangles from back to front
		sort(vecTrianglesToRaster.begin(), vecTrianglesToRaster.end(), [](triangle &t1, triangle &t2)
		{
			float z1 = (t1.p[0].z + t1.p[1].z + t1.p[2].z) / 3.0f;
			float z2 = (t2.p[0].z + t2.p[1].z + t2.p[2].z) / 3.0f;
			return z1 > z2;
		});

		// Clear Screen
		Fill(0, 0, ScreenWidth(), ScreenHeight(), PIXEL_SOLID, FG_BLACK);

		// Loop through all transformed, viewed, projected, and sorted triangles
		for (auto &triToRaster : vecTrianglesToRaster)
		{
			// Clip triangles against all four screen edges, this could yield
			// a bunch of triangles, so create a queue that we traverse to 
			//  ensure we only test new triangles generated against planes
			triangle clipped[2];
			list<triangle> listTriangles;

			// Add initial triangle
			listTriangles.push_back(triToRaster);
			int nNewTriangles = 1;

			for (int p = 0; p < 4; p++)
			{
				int nTrisToAdd = 0;
				while (nNewTriangles > 0)
				{
					// Take triangle from front of queue
					triangle test = listTriangles.front();
					listTriangles.pop_front();
					nNewTriangles--;

					// Clip it against a plane. We only need to test each 
					// subsequent plane, against subsequent new triangles
					// as all triangles after a plane clip are guaranteed
					// to lie on the inside of the plane. I like how this
					// comment is almost completely and utterly justified
					switch (p)
					{
					case 0:	nTrisToAdd = Triangle_ClipAgainstPlane({ 0.0f, 0.0f, 0.0f }, { 0.0f, 1.0f, 0.0f }, test, clipped[0], clipped[1]); break;
					case 1:	nTrisToAdd = Triangle_ClipAgainstPlane({ 0.0f, (float)ScreenHeight() - 1, 0.0f }, { 0.0f, -1.0f, 0.0f }, test, clipped[0], clipped[1]); break;
					case 2:	nTrisToAdd = Triangle_ClipAgainstPlane({ 0.0f, 0.0f, 0.0f }, { 1.0f, 0.0f, 0.0f }, test, clipped[0], clipped[1]); break;
					case 3:	nTrisToAdd = Triangle_ClipAgainstPlane({ (float)ScreenWidth() - 1, 0.0f, 0.0f }, { -1.0f, 0.0f, 0.0f }, test, clipped[0], clipped[1]); break;
					}

					// Clipping may yield a variable number of triangles, so
					// add these new ones to the back of the queue for subsequent
					// clipping against next planes
					for (int w = 0; w < nTrisToAdd; w++)
						listTriangles.push_back(clipped[w]);
				}
				nNewTriangles = listTriangles.size();
			}


			// Draw the transformed, viewed, clipped, projected, sorted, clipped triangles
			for (auto &t : listTriangles)
			{
				FillTriangle(t.p[0].x, t.p[0].y, t.p[1].x, t.p[1].y, t.p[2].x, t.p[2].y, t.sym, t.col);
				//DrawTriangle(t.p[0].x, t.p[0].y, t.p[1].x, t.p[1].y, t.p[2].x, t.p[2].y, PIXEL_SOLID, FG_BLACK);
			}
		}


		return true;
	}

};




int main()
{
	olcEngine3D demo;
	if (demo.ConstructConsole(256, 240, 4, 4))
		demo.Start();
    return 0;
}