2019/11/26
1 #include <glad/glad.h>
2 #include <GLFW/glfw3.h>
3
4 #include <iostream>
5
6 void framebuffer_size_callback(GLFWwindow* window, int width, int height);
7 void processInput(GLFWwindow *window);
8
9 // settings
10 const unsigned int SCR_WIDTH = 800;
11 const unsigned int SCR_HEIGHT = 600;
12
13 const char *vertexShaderSource = "#version 330 core\n"
14 "layout (location = 0) in vec3 aPos;\n"
15 "void main()\n"
16 "{\n"
17 " gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
18 "}\0";
19 const char *fragmentShaderSource = "#version 330 core\n"
20 "out vec4 FragColor;\n"
21 "void main()\n"
22 "{\n"
23 " FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
24 "}\n\0";
25
26 int main()
27 {
28 // glfw: initialize and configure
29 // ------------------------------
30 glfwInit();
31 glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
32 glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
33 glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
34
35 #ifdef __APPLE__
36 glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
37 #endif
38
39 // glfw window creation
40 // --------------------
41 GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
42 if (window == NULL)
43 {
44 std::cout << "Failed to create GLFW window" << std::endl;
45 glfwTerminate();
46 return -1;
47 }
48 glfwMakeContextCurrent(window);
49 glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
50
51 // glad: load all OpenGL function pointers
52 // ---------------------------------------
53 if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
54 {
55 std::cout << "Failed to initialize GLAD" << std::endl;
56 return -1;
57 }
58
59
60 // build and compile our shader program
61 // ------------------------------------
62 // vertex shader
63 int vertexShader = glCreateShader(GL_VERTEX_SHADER);
64 glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
65 glCompileShader(vertexShader);
66 // check for shader compile errors
67 int success;
68 char infoLog[512];
69 glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
70 if (!success)
71 {
72 glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
73 std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
74 }
75 // fragment shader
76 int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
77 glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
78 glCompileShader(fragmentShader);
79 // check for shader compile errors
80 glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
81 if (!success)
82 {
83 glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
84 std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
85 }
86 // link shaders
87 int shaderProgram = glCreateProgram();
88 glAttachShader(shaderProgram, vertexShader);
89 glAttachShader(shaderProgram, fragmentShader);
90 glLinkProgram(shaderProgram);
91 // check for linking errors
92 glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
93 if (!success) {
94 glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
95 std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
96 }
97 glDeleteShader(vertexShader);
98 glDeleteShader(fragmentShader);
99
100 // set up vertex data (and buffer(s)) and configure vertex attributes
101 // ------------------------------------------------------------------
102 float firstTriangle[] = {
103 -0.9f, -0.5f, 0.0f, // left
104 -0.0f, -0.5f, 0.0f, // right
105 -0.45f, 0.5f, 0.0f, // top
106 };
107 float secondTriangle[] = {
108 0.0f, -0.5f, 0.0f, // left
109 0.9f, -0.5f, 0.0f, // right
110 0.45f, 0.5f, 0.0f // top
111 };
112 unsigned int VBOs[2], VAOs[2];
113 glGenVertexArrays(2, VAOs); // we can also generate multiple VAOs or buffers at the same time
114 glGenBuffers(2, VBOs);
115 // first triangle setup
116 // --------------------
117 glBindVertexArray(VAOs[0]);
118 glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
119 glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangle), firstTriangle, GL_STATIC_DRAW);
120 glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); // Vertex attributes stay the same
121 glEnableVertexAttribArray(0);
122 // glBindVertexArray(0); // no need to unbind at all as we directly bind a different VAO the next few lines
123 // second triangle setup
124 // ---------------------
125 glBindVertexArray(VAOs[1]); // note that we bind to a different VAO now
126 glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]); // and a different VBO
127 glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangle), secondTriangle, GL_STATIC_DRAW);
128 glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0); // because the vertex data is tightly packed we can also specify 0 as the vertex attribute's stride to let OpenGL figure it out
129 glEnableVertexAttribArray(0);
130 // glBindVertexArray(0); // not really necessary as well, but beware of calls that could affect VAOs while this one is bound (like binding element buffer objects, or enabling/disabling vertex attributes)
131
132
133 // uncomment this call to draw in wireframe polygons.
134 //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
135
136 // render loop
137 // -----------
138 while (!glfwWindowShouldClose(window))
139 {
140 // input
141 // -----
142 processInput(window);
143
144 // render
145 // ------
146 glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
147 glClear(GL_COLOR_BUFFER_BIT);
148
149 glUseProgram(shaderProgram);
150 // draw first triangle using the data from the first VAO
151 glBindVertexArray(VAOs[0]);
152 glDrawArrays(GL_TRIANGLES, 0, 3);
153 // then we draw the second triangle using the data from the second VAO
154 glBindVertexArray(VAOs[1]);
155 glDrawArrays(GL_TRIANGLES, 0, 3);
156
157 // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
158 // -------------------------------------------------------------------------------
159 glfwSwapBuffers(window);
160 glfwPollEvents();
161 }
162
163 // optional: de-allocate all resources once they've outlived their purpose:
164 // ------------------------------------------------------------------------
165 glDeleteVertexArrays(2, VAOs);
166 glDeleteBuffers(2, VBOs);
167
168 // glfw: terminate, clearing all previously allocated GLFW resources.
169 // ------------------------------------------------------------------
170 glfwTerminate();
171 return 0;
172 }
173
174 // process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
175 // ---------------------------------------------------------------------------------------------------------
176 void processInput(GLFWwindow *window)
177 {
178 if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
179 glfwSetWindowShouldClose(window, true);
180 }
181
182 // glfw: whenever the window size changed (by OS or user resize) this callback function executes
183 // ---------------------------------------------------------------------------------------------
184 void framebuffer_size_callback(GLFWwindow* window, int width, int height)
185 {
186 // make sure the viewport matches the new window dimensions; note that width and
187 // height will be significantly larger than specified on retina displays.
188 glViewport(0, 0, width, height);
189 }