opengl 画个立方体
opengl 画个立方体
使用opengl画立方体，实际是画多个三角形，让三角形最终拼接成一个立方体。
#include "glew.h"
#include
#include "common/loadShader.h"
#include "glm.hpp"
#include "ext.hpp"
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(480, 320, "Hello World", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
// Needed in core profile
if( glewInit() != GLEW_OK)
{
glfwTerminate();
return -1;
}
// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
static const GLfloat g_vertex_buffer_data[] = {
-1.0f,-1.0f,-1.0f, //triangle 1 : begin
-1.0f,-1.0f,1.0f,
-1.0f,1.0f,1.0f, //triangle 1 : end
1.0f, 1.0f,-1.0f, // triangle 2 : begin
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f,-1.0f, // triangle 2 : end
1.0f,-1.0f, 1.0f,
-1.0f,-1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, 1.0f,-1.0f,
1.0f,-1.0f, 1.0f,
-1.0f,-1.0f, 1.0f,
-1.0f,-1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f,-1.0f, 1.0f,
1.0f,-1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f,-1.0f,
1.0f,-1.0f,-1.0f,
1.0f, 1.0f, 1.0f,
1.0f,-1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f,-1.0f,
-1.0f, 1.0f,-1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f,-1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f,-1.0f, 1.0f
};
//This will identify our vertex buffer
GLuint vertexbuffer;
//Generate 1 buffer,put the resulting identifier in vertexbuffer
glGenBuffers(1,&vertexbuffer);
//The following commands will talk about our 'vertexbuffer' buffer
glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer);
//Give our vertices to OpenGL.
glBufferData(GL_ARRAY_BUFFER,sizeof(g_vertex_buffer_data),g_vertex_buffer_data,GL_STATIC_DRAW);
// One color for each vertex. They were generated randomly.
static const GLfloat g_color_buffer_data[] = {
0.583f, 0.771f, 0.014f,
0.609f, 0.115f, 0.436f,
0.327f, 0.483f, 0.844f,
0.822f, 0.569f, 0.201f,
0.435f, 0.602f, 0.223f,
0.310f, 0.747f, 0.185f,
0.597f, 0.770f, 0.761f,
0.559f, 0.436f, 0.730f,
0.359f, 0.583f, 0.152f,
0.483f, 0.596f, 0.789f,
0.559f, 0.861f, 0.639f,
0.195f, 0.548f, 0.859f,
0.014f, 0.184f, 0.576f,
0.771f, 0.328f, 0.970f,
0.406f, 0.615f, 0.116f,
0.676f, 0.977f, 0.133f,
0.971f, 0.572f, 0.833f,
0.140f, 0.616f, 0.489f,
0.997f, 0.513f, 0.064f,
0.945f, 0.719f, 0.592f,
0.543f, 0.021f, 0.978f,
0.279f, 0.317f, 0.505f,
0.167f, 0.620f, 0.077f,
0.347f, 0.857f, 0.137f,
0.055f, 0.953f, 0.042f,
0.714f, 0.505f, 0.345f,
0.783f, 0.290f, 0.734f,
0.722f, 0.645f, 0.174f,
0.302f, 0.455f, 0.848f,
0.225f, 0.587f, 0.040f,
0.517f, 0.713f, 0.338f,
0.053f, 0.959f, 0.120f,
0.393f, 0.621f, 0.362f,
0.673f, 0.211f, 0.457f,
0.820f, 0.883f, 0.371f,
0.982f, 0.099f, 0.879f
};
GLuint colorbuffer;
glGenBuffers(1,&colorbuffer);
glBindBuffer(GL_ARRAY_BUFFER,colorbuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(g_color_buffer_data),g_color_buffer_data,GL_STATIC_DRAW);
GLuint programID = LoadShaders("./shader/vertex.shader","./shader/fragment.shader");
glUseProgram(programID);
glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
/* Loop until the user closes the window */
// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit 100 units
//glm::mat4 Projection = glm::ortho(-4.0f/3.0f, 4.0f/3.0f, -1.0f, 1.0f, 0.1f, 100.0f);
glm::mat4 Projection = glm::perspective(45.0f,4.0f/3.0f,0.1f,100.f);
glm::mat4 View = glm::lookAt(
glm::vec3(4,3,-3), // Camera is at (4,3,3), in World Space
glm::vec3(0,0,0), // and looks at the origin
glm::vec3(0,1,0) // Head is up (set to 0,-1,0 to look upside-down)
);
//Model matrix : an identity matrix (model will be at the origin)
glm::mat4 Model = glm::mat4(1.0f);
// Our ModelViewProjection : multiplication of our 3 matrices
glm::mat4 MVP = Projection * View * Model;// Remember, matrix multiplication is the other way around
// Get a handle for our "MVP" uniform.
// Only at initialisation time.
GLuint MatrixID = glGetUniformLocation(programID,"MVP");
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
// For each model you render, since the MVP will be different (at least the M part)
glUniformMatrix4fv(MatrixID,1,GL_FALSE,&MVP[0][0]);
while (!glfwWindowShouldClose(window))
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer);
glVertexAttribPointer(
0, // attribute 0. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER,colorbuffer);
glVertexAttribPointer(
1, // attribute 0. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
glDrawArrays(GL_TRIANGLES,0,12*3);// Starting from vertex 0; 3 vertices total -> 1 triangle
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
} vertex.shader
version 330 core
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColor;
uniform mat4 MVP;
out vec3 fragmentColor;
void main(){
vec4 v = vec4(vertexPosition_modelspace,1);
gl_Position = MVP * v;
// The color of each vertex will be interpolated
// to produce the color of each fragment
fragmentColor = vertexColor;
}fragment.shader
out vec3 color;
in vec3 fragmentColor;
void main(){
color = fragmentColor;
}
首先，设置顶点位置，然后设置顶点颜色，glVertexAttribPointer将数据传入shader中，vertex.shader将顶点颜色输出到fragment.shader中。注意，glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LESS); 开启深度测试，最后的三角形会根据z轴位置确定遮挡关系，如果没有这句三角形会根据画的先后顺序确定遮挡关系。