OpenGL draws colored triangles

Use openGL Drawing graphics requires three steps ：
1. Create a VBO, Make the data in memory , Save to the graphics card cache ;VBO Our task is this one thing ;
2. Create a VAO, That is, the array of attributes , Be responsible for putting the existing data , Binding properties , Specify the rules for using data , Make the shader understand that those data are colors , Those are coordinates ;
3. Shader program , Running on the GPU in , Be responsible for putting the existing data , Calculate and render the image ;

Draw a triangle with different vertex colors , You need to set a color for every vertex of the triangle , This also requires some color data . We can define vertex data and color data separately .

    GLfloat ver[] = {
    
		// If there are two triangles , Conventional drawing method , Define the position points of two triangles 
		// The first triangle 
		0.0f,  0.5f, 0.0f,
		-0.5f, -0.5f, 0.0f,
		0.5f, -0.5f, 0.0f,
	};

	GLfloat verColor[] = {
    
		1.0f,  0.0f, 0.0f, 1.0f,
		0.0f,  1.0f, 0.0f, 1.0f,
		0.0f,  0.0f, 1.0f, 1.0f,
	};

Take a look at the painting effect ：

#pragma once
#include <QOpenGLWindow>
#include <QOpenGLShader>
#include <QOpenGLShaderProgram>
class QOpenGLFunctions_3_3_Core;

class HelloShaderSelf : public QOpenGLWindow {
    
	Q_OBJECT

public:
	HelloShaderSelf();
	~HelloShaderSelf();

private:
	void initializeGL();
	void resizeGL(int w, int h);
	void paintGL();

private:
	QOpenGLFunctions_3_3_Core* _openGLCore;
	GLuint _VBO;// Vertex Position VBO
	GLuint _VBOColor;// Vertex color VBO
	GLuint _VAO;
	QOpenGLShaderProgram _shaderProgram;// Shader program , All shaders in the system 
};

#include <QOpenGLFunctions_3_3_Core>
#include <QVector4D>
#include <QMath.h>
#include "HelloShaderSelf.h"

HelloShaderSelf::HelloShaderSelf() {
    
}

HelloShaderSelf::~HelloShaderSelf() {
    
}

void HelloShaderSelf::initializeGL() {
    
	_openGLCore = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_3_Core>();

	GLfloat ver[] = {
    
		// If there are two triangles , Conventional drawing method , Define the position points of two triangles 
		// The first triangle 
		0.0f,  0.5f, 0.0f,
		-0.5f, -0.5f, 0.0f,
		0.5f, -0.5f, 0.0f,
	};

	GLfloat verColor[] = {
    
		1.0f,  0.0f, 0.0f, 1.0f,
		0.0f,  1.0f, 0.0f, 1.0f,
		0.0f,  0.0f, 1.0f, 1.0f,
	};

	_openGLCore->glGenBuffers(1, &_VAO);
	_openGLCore->glGenBuffers(1, &_VBO);
	_openGLCore->glGenBuffers(1, &_VBOColor);

	_openGLCore->glBindVertexArray(_VAO);
	
	// Write the location data into the graphics card cache 
	_openGLCore->glBindBuffer(GL_ARRAY_BUFFER, _VBO);
	_openGLCore->glBufferData(GL_ARRAY_BUFFER, sizeof(ver), ver, GL_STATIC_DRAW);
	_openGLCore->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (void*)0);
	_openGLCore->glEnableVertexAttribArray(0);

	// Write vertex color data to the graphics card cache 
	_openGLCore->glBindBuffer(GL_ARRAY_BUFFER, _VBOColor);
	_openGLCore->glBufferData(GL_ARRAY_BUFFER, sizeof(verColor), verColor, GL_STATIC_DRAW);
	_openGLCore->glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (void*)0);
	_openGLCore->glEnableVertexAttribArray(1);

	_openGLCore->glBindVertexArray(0);

	QOpenGLShader vertexShager(QOpenGLShader::Vertex);// Vertex shader 
	vertexShager.compileSourceFile("E:/Projects/QtGuiTest/OPenGLApp/shader/HelloShaderSelf.vert");
	QOpenGLShader fragmentShager(QOpenGLShader::Fragment);// Fragment Shader 
	fragmentShager.compileSourceFile("E:/Projects/QtGuiTest/OPenGLApp/shader/HelloShaderSelf.frag");
	_shaderProgram.addShader(&vertexShager);
	_shaderProgram.addShader(&fragmentShager);

	_shaderProgram.link();
}

void HelloShaderSelf::resizeGL(int w, int h) {
    

}

void HelloShaderSelf::paintGL() {
    
	_openGLCore->glClearColor(0.6f, 0.6f, 0.6f, 1.0);
	_openGLCore->glClear(GL_COLOR_BUFFER_BIT);

	_shaderProgram.bind();

	
	_openGLCore->glBindVertexArray(_VAO);



	_openGLCore->glDrawArrays(GL_TRIANGLES, 0, 3);

	update();
}

Vertex shader ：

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec4 aColor;
out vec4 outColor;
void main(){
    
	gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
	outColor = aColor;
}

Chip shader ：

#version 330 core
out vec4 fragColor;
in vec4 outColor;// Color passed from vertex shader 

void main(){
    
	fragColor = outColor;
}

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