QT中学习Opengl---（绘制练习部分）
前言：
本文的代码是 LearnOpenGL 中对应代码，这里提供学习，大家喜欢的可去官方网站去看看:
https://learnopengl-cn.readthedocs.io/zh/latest/
https://learnopengl-cn.readthedocs.io/zh/latest/本文是对应练习题目的三个代码部分。
- 尝试使用 glDrawArrays 以在你的数据中添加更多顶点的方式， 绘制两个彼此相连的三角
形 - 使用不同的VAO(和VBO)创建同样的2个三角形， 每个三角形的数据要不同(提示：
创建2个顶点数据数组， 而不是1个) - 创建连个着色器程序(Shader Program)， 第二个程序使用不同的片段着色器， 它输出黄
色； 绘制这两个三角形， 其中一个输出为黄色
题目1 ：
尝试使用 glDrawArrays 以在你的数据中添加更多顶点的方式， 绘制两个彼此相连的三角
形。
绘制结果：
代码部分：
#include "bkqopenglw.h"
#include
float vertices[] = {
// first triangle
-0.9f, -0.5f, 0.0f, // left
-0.0f, -0.5f, 0.0f, // right
-0.45f, 0.5f, 0.0f, // top
// second triangle
0.0f, -0.5f, 0.0f, // left
0.9f, -0.5f, 0.0f, // right
0.45f, 0.5f, 0.0f // top
};
//顶点着色器
const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
//片段着色器
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";
BKQOpenglW::BKQOpenglW(QWidget *parent) : QOpenGLWidget(parent)
{
}
void BKQOpenglW::initializeGL()
{
initializeOpenGLFunctions();
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), nullptr);
glEnableVertexAttribArray(0);
// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0);
// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
glBindVertexArray(0);
//创建顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader,1,&vertexShaderSource,(nullptr));
glCompileShader(vertexShader);
int success;
char infoLog[512];
glGetShaderiv(vertexShader,GL_COMPILE_STATUS,&success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//创建片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr);
glCompileShader(fragmentShader);
// check for shader compile errors
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//链接着色器
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram,vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
}
void BKQOpenglW::resizeGL(int w, int h)
{
glViewport(0,0,w,h);
}
void BKQOpenglW::paintGL()
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES,0,6);
}
就是改变了顶点，然后 glDrawArrays(GL_TRIANGLES,0,6); 3变成6就可以了。
题目2：
使用不同的VAO(和VBO)创建同样的2个三角形， 每个三角形的数据要不同(提示：
创建2个顶点数据数组， 而不是1个)
输出结果：
代码：
#include "bkqopenglw.h"
#include
float firstTriangle[] = {
-0.9f, -0.5f, 0.0f, // left
-0.0f, -0.5f, 0.0f, // right
-0.45f, 0.5f, 0.0f, // top
};
float secondTriangle[] = {
0.0f, -0.5f, 0.0f, // left
0.9f, -0.5f, 0.0f, // right
0.45f, 0.5f, 0.0f // top
};
//顶点着色器
const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
//片段着色器
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";
BKQOpenglW::BKQOpenglW(QWidget *parent) : QOpenGLWidget(parent)
{
}
void BKQOpenglW::initializeGL()
{
initializeOpenGLFunctions();
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangle), firstTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), nullptr);
glEnableVertexAttribArray(0);
glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangle), secondTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
glEnableVertexAttribArray(0);
// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0);
// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
glBindVertexArray(0);
//创建顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader,1,&vertexShaderSource,(nullptr));
glCompileShader(vertexShader);
int success;
char infoLog[512];
glGetShaderiv(vertexShader,GL_COMPILE_STATUS,&success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//创建片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr);
glCompileShader(fragmentShader);
// check for shader compile errors
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//链接着色器
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram,vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
}
void BKQOpenglW::resizeGL(int w, int h)
{
glViewport(0,0,w,h);
}
void BKQOpenglW::paintGL()
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
glBindVertexArray(VAO[0]);
glDrawArrays(GL_TRIANGLES,0,3);
glBindVertexArray(VAO[1]);
glDrawArrays(GL_TRIANGLES,0,3);
}
题目3：
创建连个着色器程序(Shader Program)， 第二个程序使用不同的片段着色器， 它输出黄
色； 绘制这两个三角形， 其中一个输出为黄色
输出结果：
代码部分：
#include "bkqopenglw.h"
#include
float firstTriangle[] = {
-0.9f, -0.5f, 0.0f, // left
-0.0f, -0.5f, 0.0f, // right
-0.45f, 0.5f, 0.0f, // top
};
float secondTriangle[] = {
0.0f, -0.5f, 0.0f, // left
0.9f, -0.5f, 0.0f, // right
0.45f, 0.5f, 0.0f // top
};
//顶点着色器
const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
//片段着色器
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";
const char *fragmentShader2Source = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 1.0f, 0.0f, 1.0f);\n"
"}\n\0";
BKQOpenglW::BKQOpenglW(QWidget *parent) : QOpenGLWidget(parent)
{
}
void BKQOpenglW::initializeGL()
{
initializeOpenGLFunctions();
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangle), firstTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), nullptr);
glEnableVertexAttribArray(0);
glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangle), secondTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 12, nullptr);
glEnableVertexAttribArray(0);
// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0);
// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
glBindVertexArray(0);
//创建顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader,1,&vertexShaderSource,(nullptr));
glCompileShader(vertexShader);
int success;
char infoLog[512];
glGetShaderiv(vertexShader,GL_COMPILE_STATUS,&success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//创建片段着色器
unsigned int fragmentShaderOrange = glCreateShader(GL_FRAGMENT_SHADER);
unsigned int fragmentShaderYellow = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShaderOrange, 1, &fragmentShaderSource, nullptr);
glShaderSource(fragmentShaderYellow, 1, &fragmentShader2Source, nullptr);
glCompileShader(fragmentShaderOrange);
glCompileShader(fragmentShaderYellow);
// check for shader compile errors
glGetShaderiv(fragmentShaderOrange, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShaderOrange, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//链接着色器
shaderProgramOrange = glCreateProgram();
shaderProgramYellow = glCreateProgram();
glAttachShader(shaderProgramOrange,vertexShader);
glAttachShader(shaderProgramYellow,vertexShader);
glAttachShader(shaderProgramOrange, fragmentShaderOrange);
glAttachShader(shaderProgramYellow, fragmentShaderYellow);
glLinkProgram(shaderProgramOrange);
glLinkProgram(shaderProgramYellow);
glGetProgramiv(shaderProgramOrange, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgramOrange, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(shaderProgramOrange);
}
void BKQOpenglW::resizeGL(int w, int h)
{
glViewport(0,0,w,h);
}
void BKQOpenglW::paintGL()
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgramOrange);
glBindVertexArray(VAO[0]);
glDrawArrays(GL_TRIANGLES,0,3);
glUseProgram(shaderProgramYellow);
glBindVertexArray(VAO[1]);
glDrawArrays(GL_TRIANGLES,0,3);
}
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