wireframe cube

CMakeLists.txt

@@ -13,7 +13,7 @@ file(GLOB SOURCES "src/*.c")
 add_executable(renderer ${SOURCES})
 
 # Link SDL2 library to the executable
-target_link_libraries(renderer PRIVATE ${SDL2_LIBRARIES})
+target_link_libraries(renderer PRIVATE ${SDL2_LIBRARIES} m)
 
 # Set compiler options
 target_compile_options(renderer PRIVATE -Wall -g)  # -g adds debugging information

Makefile

@@ -1,7 +1,7 @@
 SRCS = $(shell find ./src -type f -name *.c)
 
 build:
-	gcc -Wall -std=c99 $(SRCS) -lSDL2 -o renderer
+	gcc -Wall -std=c99 $(SRCS) -lSDL2 -lm -o renderer
 	./renderer
 
 run: build

src/display.c

@@ -105,3 +105,25 @@ void destroy_window(void) {
     SDL_Quit();
 }
 
+
+void draw_line(int x0, int y0, int x1, int y1, uint32_t color) {
+    int delta_x = x1-x0;
+    int delta_y = y1-y0;
+    int longest_side_length = abs(delta_x) >= abs(delta_y) ? abs(delta_x) : abs(delta_y);
+
+    float xInc = delta_x / (float)longest_side_length;
+    float yInc = delta_y / (float)longest_side_length;
+    float current_x = x0;
+    float current_y = y0;
+    for (int i = 0; i < longest_side_length; i++) {
+        draw_pixel(round(current_x), round(current_y), color);
+        current_x += xInc;
+        current_y += yInc;
+    }
+}
+
+void draw_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t color){
+     draw_line(x0, y0, x1, y1, color);
+     draw_line(x1, y1, x2, y2, color);
+     draw_line(x2, y2, x0, y0, color);
+}

src/display.h

@@ -12,6 +12,8 @@ extern uint32_t *color_buffer;
 extern SDL_Texture *color_buffer_texture;
 extern int window_width;
 extern int window_height;
+#define FPS 60
+#define FRAME_TARGET_TIME (1000/FPS)
 
 bool initialize_window(void);
 
@@ -19,6 +21,8 @@ void draw_grid();
 
 void draw_pixel(int x, int y, uint32_t color);
 
+void draw_line(int x0, int y0, int x1, int y1, uint32_t color);
+void draw_triangle(int x0, int y0, int x1, int y1, int x2, int y2, uint32_t color);
 void draw_rect(int x, int y, int width, int height, uint32_t color);
 
 void clear_color_buffer(uint32_t color);

src/main.c

@@ -3,112 +3,129 @@
 #include <SDL2/SDL.h>
 #include "display.h"
 #include "vector.h"
-
-////////////////////////////////////////////////////////////
-// Declare an array of points
-////////////////////////////////////////////////////////////
-#define N_POINTS  (9 * 9 * 9)
-vec3_t cube_points[N_POINTS];
-vec2_t projected_points[N_POINTS];
+#include "mesh.h"
 
 vec3_t camera_position = {0, 0, -5};
+vec3_t cube_rotation = {.x = 0, .y = 0, .z = 0};
+triangle_t triangles_to_render[N_MESH_FACES];
 float fov_factor = 640;
-
-
 bool is_running = false;
+uint32_t previous_frame_time = 0;
+
 
 void setup(void) {
-	// Allocate the required memory in bytes to hold color buffer
-	color_buffer = (uint32_t *) malloc(sizeof(uint32_t) * window_width * window_height);
+    // Allocate the required memory in bytes to hold color buffer
+    color_buffer = (uint32_t *) malloc(sizeof(uint32_t) * window_width * window_height);
 
-	// Creating the SDL Texture that is uses to display the color buffer
-	color_buffer_texture = SDL_CreateTexture(
-		renderer,
-		SDL_PIXELFORMAT_ARGB8888,
-		SDL_TEXTUREACCESS_STREAMING,
-		window_width,
-		window_height
-	);
-	int point_count = 0;
-	for (float x = -1; x <= 1; x += 0.25) {
-		for (float y = -1; y <= 1; y += 0.25) {
-			for (float z = -1; z <= 1; z += 0.25) {
-				vec3_t new_point = { .x = x, .y = y, .z = z };
-				cube_points[point_count++] = new_point;
-			}
-		}
-	}
+    // Creating the SDL Texture that is uses to display the color buffer
+    color_buffer_texture = SDL_CreateTexture(
+            renderer,
+            SDL_PIXELFORMAT_ARGB8888,
+            SDL_TEXTUREACCESS_STREAMING,
+            window_width,
+            window_height
+    );
 }
 
 void process_input(void) {
-	SDL_Event event;
-	SDL_PollEvent(&event);
+    SDL_Event event;
+    SDL_PollEvent(&event);
 
-	switch (event.type) {
-		case SDL_QUIT:
-			is_running = false;
-		break;
-		case SDL_KEYDOWN:
-			if (event.key.keysym.sym == SDLK_ESCAPE) {
-				is_running = false;
-			}
-		break;
-	}
+    switch (event.type) {
+        case SDL_QUIT:
+            is_running = false;
+            break;
+        case SDL_KEYDOWN:
+            if (event.key.keysym.sym == SDLK_ESCAPE) {
+                is_running = false;
+            }
+            break;
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Function that receives a 3d Vector and returns a 2d projected point
 ////////////////////////////////////////////////////////////////////////////////
 vec2_t project(vec3_t point) {
-	vec2_t projected_point = {
-		.x = (fov_factor * point.x) / point.z,
-		.y = (fov_factor * point.y) / point.z,
-	};
-	return projected_point;
+    vec2_t projected_point = {
+            .x = (fov_factor * point.x) / point.z,
+            .y = (fov_factor * point.y) / point.z,
+    };
+    return projected_point;
 }
 
-
 void update(void) {
-	for (int i = 0; i < N_POINTS; i++){
-		vec3_t point = cube_points[i];
-    point.z -= camera_position.z;
-		vec2_t projected_point = project(point);
+    // lock execution to the next tick
+    uint32_t time_to_wait = FRAME_TARGET_TIME - (SDL_GetTicks() - previous_frame_time);
+    if (time_to_wait > 0 && time_to_wait <= FRAME_TARGET_TIME) {
+        SDL_Delay(time_to_wait);
+    }
+    previous_frame_time = SDL_GetTicks();
+
+    cube_rotation.y += 0.01f;
+    cube_rotation.z += 0.01f;
+    cube_rotation.x += 0.01f;
+
+    for (int i = 0; i < N_MESH_FACES; i++) {
+        face_t mesh_face = mesh_faces[i];
+        vec3_t face_vertices[3];
+        face_vertices[0] = mesh_vertices[mesh_face.a - 1];
+        face_vertices[1] = mesh_vertices[mesh_face.b - 1];
+        face_vertices[2] = mesh_vertices[mesh_face.c - 1];
+        //loop all three vertices
+        triangle_t projected_triangle;
+        for (int j = 0; j < 3; j++) {
+            vec3_t transformed_vertex = face_vertices[j];
+            transformed_vertex = vec3_rotate_y(transformed_vertex, cube_rotation.y);
+            transformed_vertex = vec3_rotate_x(transformed_vertex, cube_rotation.x);
+            transformed_vertex = vec3_rotate_z(transformed_vertex, cube_rotation.z);
+            transformed_vertex.z -= camera_position.z;
+            vec2_t projected_point = project(transformed_vertex);
+
+            projected_point.x += (window_width / 2);
+            projected_point.y += (window_height / 2);
+
+            projected_triangle.points[j] = projected_point;
+        }
+        // save projected triangle in array of triangles to render
+        triangles_to_render[i] = projected_triangle;
+    }
 
-		projected_points[i] = projected_point;
-	}
 }
 
 
 void render(void) {
-	draw_grid();
+    draw_grid();
 
-	for (int i = 0; i < N_POINTS; i++){
-		vec2_t projected_point = projected_points[i];
-		draw_rect(
-			projected_point.x + (window_width/2),
-			projected_point.y + (window_height/2),
-			4,
-			4,
-			0xFFFFFF00
-		);
-	}
+    for (int i = 0; i < N_MESH_FACES; i++) {
+        triangle_t triangle = triangles_to_render[i];
+        uint32_t color = 0xFFFFFF00;
+        for (int j = 0; j < 3; j++) {
+            draw_rect(triangle.points[j].x, triangle.points[j].y, 3, 3, color);
+        }
+        draw_triangle(triangle.points[0].x, triangle.points[0].y,
+                      triangle.points[1].x, triangle.points[1].y,
+                      triangle.points[2].x, triangle.points[2].y,
+                      color);
 
-	render_color_buffer();
-	clear_color_buffer(0xFF000000);
+    }
 
-	SDL_RenderPresent(renderer);
+    render_color_buffer();
+    clear_color_buffer(0xFF000000);
+
+    SDL_RenderPresent(renderer);
 }
 
 
 int main(void) {
-	is_running = initialize_window();
-	setup();
+    is_running = initialize_window();
+    setup();
 
-	while (is_running) {
-	process_input();
-		update();
-		render();
-	}
-	destroy_window();
-	return 0;
+    while (is_running) {
+        process_input();
+        update();
+        render();
+    }
+    destroy_window();
+    return 0;
 }

src/mesh.c

@@ -0,0 +1,33 @@
+#include "mesh.h"
+
+vec3_t mesh_vertices[N_MESH_VERTICES] = {
+        {.x = -1, .y = -1, .z = -1},
+        {.x = -1, .y = 1, .z = -1},
+        {.x = 1, .y = 1, .z = -1},
+        {.x = 1, .y = -1, .z = -1},
+        {.x = 1, .y = 1, .z = 1},
+        {.x = 1, .y = -1, .z = 1},
+        {.x = -1, .y = 1, .z = 1},
+        {.x = -1, .y = -1, .z = 1},
+};
+
+face_t mesh_faces[N_MESH_FACES] = {
+        //              Front
+        {.a = 1, .b = 2, .c = 3},
+        {.a = 1, .b = 3, .c = 4},
+        //              right
+        {.a = 4, .b = 3, .c = 5},
+        {.a = 4, .b = 5, .c = 6},
+        //              back
+        {.a = 6, .b = 5, .c = 7},
+        {.a = 6, .b = 7, .c = 8},
+        //              left
+        {.a = 8, .b = 7, .c = 2},
+        {.a = 8, .b = 2, .c = 1},
+        //              top
+        {.a = 2, .b = 7, .c = 5},
+        {.a = 2, .b = 5, .c = 3},
+        //              bottom
+        {.a = 6, .b = 8, .c = 1},
+        {.a = 6, .b = 1, .c = 4},
+};

src/mesh.h

@@ -0,0 +1,11 @@
+#ifndef RENDERER_MESH_H
+#define RENDERER_MESH_H
+#include "vector.h"
+#include "triangle.h"
+#define N_MESH_VERTICES 8
+#define N_MESH_FACES (6 * 2 )
+
+extern vec3_t mesh_vertices[N_MESH_VERTICES];
+extern face_t mesh_faces[N_MESH_FACES];
+
+#endif //RENDERER_MESH_H

src/triangle.c

@@ -0,0 +1,3 @@
+#include "triangle.h"
+
+// TODO

src/triangle.h

@@ -0,0 +1,16 @@
+#ifndef RENDERER_TRIANGLE_H
+#define RENDERER_TRIANGLE_H
+
+#include "vector.h"
+
+typedef struct {
+    int a;
+    int b;
+    int c;
+} face_t;
+
+typedef struct {
+    vec2_t points[3];
+} triangle_t;
+
+#endif //RENDERER_TRIANGLE_H

src/vector.c

@@ -1,3 +1,28 @@
+#include <math.h>
 #include "vector.h"
 
 // Implement all vector functons
+vec3_t vec3_rotate_x(vec3_t v, float angle){
+	vec3_t rotated_vector = {
+		.x = v.x,
+		.y = v.y * cos(angle) - v.z * sin(angle),
+		.z = v.y * sin(angle) + v.z * cos(angle)
+	};
+	return rotated_vector;
+}
+vec3_t vec3_rotate_y(vec3_t v, float angle) {
+	vec3_t rotated_vector = {
+		.x = v.x * cos(angle) - v.z * sin(angle),
+		.y = v.y,
+		.z = v.x * sin(angle) + v.z * cos(angle)
+	};
+	return rotated_vector;
+}
+vec3_t vec3_rotate_z(vec3_t v, float angle) {
+	vec3_t rotated_vector = {
+		.x = v.x * cos(angle) - v.y * sin(angle),
+		.y = v.x * sin(angle) + v.y * cos(angle),
+		.z = v.z
+	};
+	return rotated_vector;
+}

src/vector.h

@@ -13,6 +13,9 @@ typedef struct {
   float z;
 } vec3_t;
 
+vec3_t vec3_rotate_x(vec3_t v, float angle);
+vec3_t vec3_rotate_y(vec3_t v, float angle);
+vec3_t vec3_rotate_z(vec3_t v, float angle);
 
 
 #endif