现代opengl 设计 多个着色器的使用
现代opengl 程序中，都有一个着色器，我就想是不是可以有多个着色器呢？这样就催生了本文，2个着色器的例子。
一个着色器包含顶点着色器和片段着色器。本文介绍2个着色器的使用例子，一个是纹理贴图，一个只是简单的长方体。
下面先看看效果：
现在把2个着色器代码展示出来：
纹理图的顶点着色器：
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoord;
out vec2 TexCoord;
uniform mat4 mvp;
void main()
{
gl_Position = mvp* vec4(aPos, 1.0f);
TexCoord = vec2(aTexCoord.x, aTexCoord.y);
}纹理图的片段着色器：
#version 330 core
out vec4 FragColor;
in vec2 TexCoord;
uniform sampler2D texture1;
void main()
{
FragColor = texture(texture1, TexCoord);
}
立方体的 顶点着色器：
#version 330 core
layout (location = 0) in vec3 aPos;
uniform mat4 mvp;
void main()
{
gl_Position = mvp*vec4(aPos, 1.0);
}立方体的 片段着色器：
#version 330 core
out vec4 FragColor;
uniform vec4 ourColor;
void main()
{
FragColor = ourColor;
}可以看到2个实体有不同的着色需求，纹理的需要vec3， vec2， 而后者只要一个vec3。
其实使用也很简单，先构建2个着色器，分别得到2个id， 在程序中依次使用
glUseProgram(ourShader.ID);
glUseProgram(ourShader2.ID);
整个程序附录于后。需要编译链接运行的话，你需要安装GLFW， glad， glm。
GLFW， glad 的安装设置请看 现代opengl 设计入门 准备第一个工程
GLM是OpenGL Mathematics的缩写，它是一个只有头文件的库，也就是说我们只需包含对应的头文件就行了，不用链接和编译。GLM可以在它们的网站上下载。把头文件的根目录复制到你的includes文件夹，然后你就可以使用这个库了。
程序中还用到了shader_s.h 可以在这里下载，stb_image.h可以在这里下载。
有了上面这些条件，建一个vc console工程，把下面代码复制过去就好了。还需要注意4个着色器文件的名字和路径要与程序一致，贴图文件你可以自己找个就好了，文件名和路径也要与程序中一致。也就是说程序中这5个文件的名字和路径要修改好。
程序在vc2010 上测试通过的，其他vc 应该也一样。
整个程序的代码也可以在我的网站www.liwensoft.com下载 ， 但GLFW， glad不包括在内。
#include
#include
#define STB_IMAGE_IMPLEMENTATION
#include
#include
#include
#include
#include
#include
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
int main()
{
// glfw: initialize and configure
// ------------------------------
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif
// glfw window creation
// --------------------
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "www.liwenz.com", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// glad: load all OpenGL function pointers
// ---------------------------------------
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// configure global opengl state
// -----------------------------
glEnable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// 使能深度检测，就是位置上前面能遮住后面的，而不是顺序上后面数据覆盖前面数据
// build and compile our shader zprogram
// ------------------------------------
Shader ourShader("D:\\study\\texture\\6.2.coordinate_systems.vs", "D:\\study\\texture\\6.2.coordinate_systems.fs");
Shader ourShader2("D:\\study\\texture\\vertex.vs", "D:\\study\\texture\\setcolor.fs");
// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
float vertices[] = {
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
0.5f, -0.5f, -0.5f, 1.0f, 1.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f
};
float vertices2[] = {
-0.6f, -0.6f, 0.6f,
0.6f, -0.6f, 0.6f,
-0.6f, 0.6f, 0.6f,
0.6f, 0.6f, 0.6f,
-0.6f, -0.6f, 0.8f,
0.6f, -0.6f, 0.8f,
-0.6f, 0.6f, 0.8f,
0.6f, 0.6f, 0.8f,
};
unsigned int indices[] = { // 注意索引从0开始!
0, 1, 2, // 第一个三角形
1, 2, 3, // 第二个三角形
4,5,6,5,6,7,
0,1,4,1,4,5,
2,3,6,3,6,7,
0,2,4,2,4,6,
1,3,4,3,4,7
};
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
// position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// texture coord attribute
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
// load and create a texture
// -------------------------
unsigned int texture1, texture2;
// texture 1
// ---------
glGenTextures(1, &texture1);
glBindTexture(GL_TEXTURE_2D, texture1);
// set the texture wrapping parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
// set texture filtering parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// load image, create texture and generate mipmaps
int width, height, nrChannels;
stbi_set_flip_vertically_on_load(true); // tell stb_image.h to flip loaded texture's on the y-axis.
unsigned char *data = stbi_load("lena.jpg", &width, &height, &nrChannels, 0);
if (data)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
glGenerateMipmap(GL_TEXTURE_2D);
}
else
{
std::cout << "Failed to load texture 1" << std::endl;
}
stbi_image_free(data);
// tell opengl for each sampler to which texture unit it belongs to (only has to be done once)
// -------------------------------------------------------------------------------------------
ourShader.use();
ourShader.setInt("texture1", 0);
//--------------------------------------------------
unsigned int m_iVBO2, m_iVAO2;
unsigned int m_iEBO;
glGenVertexArrays(1, &m_iVAO2);
glGenBuffers(1, &m_iVBO2);
glBindVertexArray(m_iVAO2);
glBindBuffer(GL_ARRAY_BUFFER, m_iVBO2);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glGenBuffers(1, &m_iEBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_iEBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
//--------------------------------------------------
// render loop
// -----------
while (!glfwWindowShouldClose(window))
{
// input
// -----
processInput(window);
// render
// ------
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // also clear the depth buffer now!
//着色前，清除深度缓冲 和颜色缓冲
glUseProgram(ourShader.ID);
// bind textures on corresponding texture units
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture1);
// create transformations 构造变换矩阵，先初始化为单位矩阵
glm::mat4 model = glm::mat4(1.0f); // make sure to initialize matrix to identity matrix first
glm::mat4 view = glm::mat4(1.0f);
glm::mat4 projection = glm::mat4(1.0f);
model = glm::rotate(model, (float)glfwGetTime(), glm::vec3(0.5f, 1.0f, 0.0f));//随时间旋转一个角度，构造model
//model = glm::rotate(model, glm::radians(55.0f), glm::vec3(1.0f, 0.0f, 0.0f));
view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));//将矩阵向我们要进行移动场景的反方向移动。构造view
projection = glm::perspective(glm::radians(45.0f), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);
glm::mat4 mvp=projection * view * model;
unsigned int mvpLoc = glGetUniformLocation(ourShader.ID, "mvp"); //从着色器获取 projection 地址
glUniformMatrix4fv(mvpLoc, 1, GL_FALSE, &mvp[0][0]);
// render box
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
glUseProgram(ourShader2.ID);
glUniformMatrix4fv(glGetUniformLocation(ourShader2.ID, "mvp"), 1, GL_FALSE, &mvp[0][0]);
glUniform4f(glGetUniformLocation(ourShader2.ID, "ourColor"), 0.2f, 0.5, 0.7f, 0.5f);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_iEBO);
glBindVertexArray(m_iVAO2);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);
// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
// -------------------------------------------------------------------------------
glfwSwapBuffers(window);
glfwPollEvents();
}
// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
glViewport(0, 0, width, height);
}