Ubuntu OpenGL ES实现一个矩形 Shader中v_texCoord赋值的完整代码例子 -DPDK中文网

下面是一个在 Ubuntu 上使用 OpenGL ES 实现一个矩形的完整代码示例，包括顶点着色器、片段着色器，以及 C++ 代码来创建和渲染这个矩形。该示例将演示如何使用 v_texCoord 在 Shader 中赋值。

1. 顶点着色器 (Vertex Shader)

#version 300 es
layout(location = 0) in vec4 a_position; // 顶点位置
layout(location = 1) in vec2 a_texCoord; // 输入的纹理坐标

out vec2 v_texCoord; // 向片段着色器传递的纹理坐标

void main() {
    gl_Position = a_position; // 设置顶点的位置
    v_texCoord = a_texCoord;  // 将输入的纹理坐标赋值给输出变量
}

2. 片段着色器 (Fragment Shader)

#version 300 es
precision mediump float;

in vec2 v_texCoord; // 从顶点着色器接收的纹理坐标
out vec4 fragColor; // 输出颜色

uniform sampler2D u_texture; // 输入的纹理

void main() {
    fragColor = texture(u_texture, v_texCoord); // 根据纹理坐标获取颜色值
}

3. C++ 主程序实现

以下是一个简单的 OpenGL ES 应用程序，在窗口中绘制一个带有纹理的矩形。

#include <GLES3/gl3.h>
#include <EGL/egl.h>
#include <GLFW/glfw3.h>
#include <iostream>

// Vertex data for a rectangle (two triangles)
GLfloat vertices[] = {
    // Position      // Texture coordinates
    -0.5f, -0.5f,   0.0f, 0.0f,   // Bottom-left corner
     0.5f, -0.5f,   1.0f, 0.0f,   // Bottom-right corner
    -0.5f,  0.5f,   0.0f, 1.0f,   // Top-left corner
    
     0.5f, -0.5f,   1.0f, 0.0f,   // Bottom-right corner
     0.5f,  0.5f,   1.0f, 1.0f,   // Top-right corner  
    -0.5f,  0.5f,   0.0f, 1.0f    // Top-left corner 
};

// Load shader from source code and compile it.
GLuint loadShader(GLenum type, const char *shaderSrc) {
    GLuint shader = glCreateShader(type);
    glShaderSource(shader, 1, &shaderSrc, nullptr);
    glCompileShader(shader);
    
    GLint success;
    glGetShaderiv(shader, GL_COMPILE_STATUS,&success);
    
    if (!success) {
        char infoLog[512];
        glGetShaderInfoLog(shader,sizeof(infoLog),nullptr ,infoLog);
        std::cerr << "ERROR::SHADER::COMPILATION_FAILED\n" << infoLog << std::endl;
        return -1;
    }
    
    return shader;
}

int main() {
    glfwInit();
    
#ifdef __APPLE__
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR ,3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR ,2);
#else 
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR ,3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR ,3);
#endif
	
	GLFWwindow* window = glfwCreateWindow(800 ,600 ,"OpenGL ES Rectangle" ,NULL ,NULL);
	if(!window) {
		std::cerr << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	
	glfwMakeContextCurrent(window);

	// Vertex Array Object and Vertex Buffer Object setup.
	GLuint VAO ,VBO;
	glGenVertexArrays(1,&VAO);
	glGenBuffers(1,&VBO);

	glBindVertexArray(VAO);

	glBindBuffer(GL_ARRAY_BUFFER,VBO);
	glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices ,GL_STATIC_DRAW);

	// Define the vertex attributes.
	glVertexAttribPointer(0 ,2 ,GL_FLOAT ,GL_FALSE ,4 * sizeof(GLfloat),(void*)nullptr);            // Position attribute layout(location=0)
	glEnableVertexAttribArray(0); 

	glVertexAttribPointer(1 ,2 ,GL_FLOAT ,GL_FALSE ,4 * sizeof(GLfloat),(void*)(2 * sizeof(GLfloat)));       // Texture coordinate attribute layout(location=1)
	glEnableVertexAttribArray(1); 

	const char *vertexShaderSrc = /* Your vertex shader code */;
	const char *fragmentShaderSrc = /* Your fragment shader code */;

	GLuint vertexShader = loadShader(GL_VERTEX_SHADER，vertexShaderSrc );
	GLuint fragmentShader = loadShader(GL_FRAGMENT_SHADER，fragmentShaderSrc );

	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram，vertexShader );
	glAttachShader(shaderProgram，fragmentShader );
	glLinkProgram(shaderProgram );

	while (!glfwWindowShouldClose(window)) {
	    glClear(GL_COLOR_BUFFER_BIT);

	    glUseProgram(shaderProgram );
	    glBindVertexArray(VAO);

	    glDrawArrays(GL_TRIANGLES，offsetof(Vertex)*6 ，6 ); 

	    glfwSwapBuffers(window );
	    glfwPollEvents();
	}

	// Cleanup resources.
glDeleteVertexArrays(1，&VAO );
glDeleteBuffers(1，&VBO );
glDeleteProgram(shaderProgram );

	free(vertex_shader_src );
	free(fragment_shader_src );

glfwTerminate();

return EXIT_SUCCESS ;
}