Add flat shading with ambient and diffuse light

Makefile

@@ -36,7 +36,8 @@ WARNINGS_OFF=-Wno-missing-braces -Wno-gnu-anonymous-struct -Wno-old-style-cast\
 CFLAGS=$(D) $(O) -std=c++11 $(WARNINGS_ON) $(WARNINGS_OFF) -I$(INCLUDE_DIR)
 LIBS=-lSDL2
 
-_HEADERS = color.h engine.h geometry.h loader.h platform.h point.h transform.h util.h
+_HEADERS = color.h engine.h geometry.h light.h loader.h platform.h point.h\
+		   transform.h util.h vec.h
 HEADERS = $(patsubst %,$(INCLUDE_DIR)/%,$(_HEADERS))
 
 _OBJS = engine.o geometry.o loader.o main.o platform.o transform.o

include/color.h

@@ -1,5 +1,6 @@
 #ifndef COLOR_H
 
+#include "util.h"
 #include <cstdint>
 
 
@@ -9,16 +10,65 @@ struct ColorU32
     {
         struct
         {
-            uint8_t b;
-            uint8_t g;
-            uint8_t r;
-            uint8_t a;
+            uint8_t b, g, r, a;
         };
 
         uint32_t u32;
     };
 };
 
+struct ColorF32
+{
+    float b, g, r, a;
+
+    static inline ColorU32 ConvertToU32(ColorF32 c)
+    {
+        ColorU32 result;
+
+        result.b = (uint8_t)(c.b * 255);
+        result.g = (uint8_t)(c.g * 255);
+        result.r = (uint8_t)(c.r * 255);
+        result.a = (uint8_t)(c.a * 255);
+
+        return result;
+    }
+};
+
+
+// OPERATORS
+// c1 + c2
+inline ColorF32 operator+(ColorF32 c1, ColorF32 c2)
+{
+    ColorF32 result;
+
+    result.b = MIN((c1.b + c2.b), 1.0f);
+    result.g = MIN((c1.g + c2.g), 1.0f);
+    result.r = MIN((c1.r + c2.r), 1.0f);
+    result.a = MIN((c1.a + c2.a), 1.0f);
+
+    return result;
+}
+
+// c1 += c2
+inline ColorF32 &operator+=(ColorF32 &c1, ColorF32 c2)
+{
+    c1 = c1 + c2;
+
+    return(c1);
+}
+
+// c * f
+inline ColorF32 operator*(ColorF32 c, float f)
+{
+    ColorF32 result;
+
+    result.b = MIN((f * c.b), 1.0f);
+    result.g = MIN((f * c.g), 1.0f);
+    result.r = MIN((f * c.r), 1.0f);
+    result.a = MIN((f * c.a), 1.0f);
+
+    return result;
+}
 
 #define COLOR_H
 #endif

include/geometry.h

@@ -1,14 +1,22 @@
 #ifndef GEOMETRY_H
 
+#include "color.h"
 #include "point.h"
 #include <cstdint>
 #include <vector>
 
 
 // STRUCTURES
+struct Material
+{
+    ColorF32 kAmbient;
+    ColorF32 kDiffuse;
+};
+
 struct Face
 {
     unsigned int vertIndex[3];
+    ColorU32 color;
 };
 
 struct Mesh
@@ -26,12 +34,44 @@ struct Mesh
         scale = 1.0f;
     }
 
+    inline void CullBackfaces(Point camPosition)
+    {
+        culledFaces.clear();
+
+        for (size_t f = 0; f < faces.size(); ++f)
+        {
+            unsigned int v0 = faces[f].vertIndex[0];
+            unsigned int v1 = faces[f].vertIndex[1];
+            unsigned int v2 = faces[f].vertIndex[2];
+
+            Vector v01 = vertsTransformed[v1] - vertsTransformed[v0];
+            Vector v02 = vertsTransformed[v2] - vertsTransformed[v0];
+
+            Vector normal = Vector::Cross(v01, v02);
+
+            // Invert for Blender-compatibility
+            normal = -normal;
+
+            // Eye vector to viewport
+            Vector view = camPosition - vertsTransformed[v0];
+
+            float dot = Vector::Dot(normal, view);
+
+            if (dot < EPSILON_E3)
+            {
+                culledFaces.push_back(faces[f]);
+            }
+        }
+    }
+
     Point position;
     float rotation[3];
     float scale;
     std::vector<Point> verts;
     std::vector<Point> vertsTransformed;
     std::vector<Face> faces;
+    std::vector<Face> culledFaces;
+    Material material;
 };
 
 

include/light.h

@@ -0,0 +1,51 @@
+#ifndef LIGHT_H
+
+
+#include "color.h"
+#include "vec.h"
+#include <cstdint>
+
+
+// STRUCTURES
+struct LightAmbient
+{
+    inline ColorF32 ComputeColor(ColorF32 reflectivity)
+    {
+        ColorF32 result;
+
+        result = reflectivity * intensity;
+
+        return result;
+    }
+
+    float intensity;
+};
+
+struct LightDiffuse
+{
+    inline ColorF32 ComputeColor(ColorF32 reflectivity, Vector normal)
+    {
+        ColorF32 result;
+
+        float dot = Vector::Dot(normal, direction);
+
+        result = reflectivity * intensity * dot;
+
+        return result;
+    }
+
+    float intensity;
+    Vector direction;
+};
+
+struct LightList
+{
+    LightAmbient ambient;
+    LightDiffuse *diffuse;
+    int diffuseCount;
+};
+
+
+#define LIGHT_H
+#endif
+

include/point.h

@@ -1,5 +1,7 @@
 #ifndef POINT_H
 
+#include "vec.h"
+
 
 // STRUCTURE
 struct Point
@@ -34,6 +36,18 @@ inline Point operator/(Point v, float f)
     return result;
 }
 
+// v1 - v2
+inline Vector operator-(Point v1, Point v2)
+{
+    Vector result;
+
+    result.x = v1.x - v2.x;
+    result.y = v1.y - v2.y;
+    result.z = v1.z - v2.z;
+
+    return result;
+}
+
 
 #define POINT_H
 #endif

include/util.h

@@ -13,6 +13,8 @@ const float EPSILON_E3 = 1E-3f;
 #define CHECK_BIT(x, bit) (x & (1UL << bit))
 #define DEG_TO_RAD(deg) ((deg * (float)M_PI) / 180.0f)
 #define SWAP(a, b, temp) {temp = a; a = b; b = temp;}
+#define MIN(a, b) ((a < b) ? a : b)
+#define MAX(a, b) ((a > b) ? a : b)
 #define FLOAT_EQUAL(a, b) ((fabsf(a - b) < EPSILON_E3) ? 1 : 0)
 
 

include/vec.h

@@ -0,0 +1,82 @@
+#ifndef VEC_H
+
+#include "util.h"
+#include <cmath>
+
+
+// STRUCTURE
+struct Vector
+{
+    inline Vector(void) : x(0), y(0), z(0), w(0) {}
+    inline Vector(float x, float y, float z) : x(x), y(y), z(z), w(0) {}
+
+    inline void Normalize(void)
+    {
+        float length = sqrtf(x*x + y*y + z*z);
+
+        // zero length
+        if (length < EPSILON_E3)
+        {
+            x = 0.0f;
+            y = 0.0f;
+            z = 0.0f;
+        }
+        else
+        {
+            float lengthInv = 1.0f / length;
+
+            x *= lengthInv;
+            y *= lengthInv;
+            z *= lengthInv;
+        }
+    }
+
+    inline static float Dot(Vector v1, Vector v2)
+    {
+        float result;
+
+        result = (v1.x * v2.x) + (v1.y * v2.y) + (v1.z * v2.z);
+
+        return result;
+    }
+
+    inline static Vector Cross(Vector v1, Vector v2)
+    {
+        Vector result;
+
+        result.x = (v1.y * v2.z) - (v1.z * v2.y);
+        result.y = (v1.z * v2.x) - (v1.x * v2.z);
+        result.z = (v1.x * v2.y) - (v1.y * v2.x);
+
+        return result;
+    }
+
+    union
+    {
+        float e[4];
+
+        struct
+        {
+            float x, y, z, w;
+        };
+    };
+};
+
+
+// OPERATORS
+// -v
+inline Vector operator-(Vector v)
+{
+    Vector result;
+
+    result.x = -v.x;
+    result.y = -v.y;
+    result.z = -v.z;
+
+    return result;
+}
+
+
+#define VEC_H
+#endif
+

src/engine.cpp

@@ -2,16 +2,19 @@
 #include "color.h"
 #include "engine.h"
 #include "geometry.h"
+#include "light.h"
 #include "loader.h"
 #include "matrix.h"
 #include "transform.h"
 #include "util.h"
+#include "vec.h"
 #include <cstdio>
 
 
 // GLOBALS
 static Mesh mesh;
 static Camera camera;
+static LightList lights;
 
 
 // PRIVATE PROTOTYPES
@@ -29,9 +32,17 @@ int Engine_Init(Engine_Buffer &buffer, char *filename)
     }
 
     mesh.position.z = 250;
+    mesh.material.kDiffuse = {1.0,1.0,1.0,1.0};
+    mesh.material.kAmbient = {1.0,1.0,1.0,1.0};
 
     camera.SetFOV(90.0f, buffer.width, buffer.height);
 
+    lights.diffuse = (LightDiffuse*)malloc(sizeof(LightDiffuse));
+    lights.diffuseCount = 1;
+    lights.ambient.intensity = 1.0;
+    lights.diffuse[0].intensity = 0.5;
+    lights.diffuse[0].direction = Vector(1,1,1);
+
     return 0;
 }
 
@@ -39,30 +50,69 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
 {
     CheckInputs(input);
 
+
+    // Local space to world space
     Matrix tTranslate = Transform_Translate(
             mesh.position.x, mesh.position.y, mesh.position.z);
 
     Matrix tRotate = Transform_Rotate(
             mesh.rotation[0], mesh.rotation[1], mesh.rotation[2]);
 
-    Matrix tScale = Transform_Scale(
-            mesh.scale);
+    Matrix tScale = Transform_Scale(mesh.scale);
 
-    Matrix tView = Transform_View(
-            camera.position, camera.rotation);
+    for (size_t v = 0; v < mesh.verts.size(); ++v)
+    {
+        mesh.vertsTransformed[v] =
+            mesh.verts[v] * tScale * tRotate * tTranslate;
+    }
 
+
+    // Cull backfaces before computing colors
+    mesh.CullBackfaces(camera.position);
+
+
+    // Color the faces (flat shading)
+    for (size_t f = 0; f < mesh.culledFaces.size(); ++f)
+    {
+        unsigned int v0 = mesh.culledFaces[f].vertIndex[0];
+        unsigned int v1 = mesh.culledFaces[f].vertIndex[1];
+        unsigned int v2 = mesh.culledFaces[f].vertIndex[2];
+
+        Vector v01 = mesh.vertsTransformed[v1] - mesh.vertsTransformed[v0];
+        Vector v02 = mesh.vertsTransformed[v2] - mesh.vertsTransformed[v0];
+
+        Vector normal = Vector::Cross(v01, v02);
+        normal.Normalize();
+
+        ColorF32 totalColor = lights.ambient.ComputeColor(mesh.material.kAmbient);
+
+        for (int c = 0; c < lights.diffuseCount; ++c)
+        {
+            totalColor += lights.diffuse[c].ComputeColor(
+                    mesh.material.kDiffuse, normal);
+        }
+
+        mesh.faces[f].color = ColorF32::ConvertToU32(totalColor);
+    }
+
+
+    // World space to camera (view) space
+    Matrix tView = Transform_View(camera.position, camera.rotation);
+
+
+    // Camera space to perspective
     Matrix tPersp = Transform_Perspective(
             camera.xZoom, camera.yZoom, camera.nearClip, camera.farClip);
 
     for (size_t v = 0; v < mesh.verts.size(); ++v)
     {
-        mesh.vertsTransformed[v] =
-            mesh.verts[v] * tScale * tRotate * tTranslate * tView * tPersp;
+        mesh.vertsTransformed[v] = mesh.vertsTransformed[v] * tView * tPersp;
 
         mesh.vertsTransformed[v] =
             mesh.vertsTransformed[v] / mesh.vertsTransformed[v].w;
     }
 
+    // Perspective to screen
     Matrix tScreen = Transform_Screen(camera.xScale, camera.yScale);
 
     for (size_t v = 0; v < mesh.verts.size(); ++v)
@@ -70,16 +120,16 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
         mesh.vertsTransformed[v] = mesh.vertsTransformed[v] * tScreen;
     }
 
-    for(size_t f = 0; f < mesh.faces.size(); ++f)
-    {
-        unsigned int v0 = mesh.faces[f].vertIndex[0];
-        unsigned int v1 = mesh.faces[f].vertIndex[1];
-        unsigned int v2 = mesh.faces[f].vertIndex[2];
 
-        ColorU32 white = {0xff,0xff,0xff,0xff};
+    // Fill each face with its respective color
+    for(size_t f = 0; f < mesh.culledFaces.size(); ++f)
+    {
+        unsigned int v0 = mesh.culledFaces[f].vertIndex[0];
+        unsigned int v1 = mesh.culledFaces[f].vertIndex[1];
+        unsigned int v2 = mesh.culledFaces[f].vertIndex[2];
 
         FillTriangle(
-                buffer.pixels, buffer.width, white.u32,
+                buffer.pixels, buffer.width, mesh.faces[f].color.u32,
                 mesh.vertsTransformed[v0].x, mesh.vertsTransformed[v0].y,
                 mesh.vertsTransformed[v1].x, mesh.vertsTransformed[v1].y,
                 mesh.vertsTransformed[v2].x, mesh.vertsTransformed[v2].y);