opengl讀取灰度圖生成三維地形

准備第三方庫 glew、freeglut、glm、opencv

准備灰度圖片和草地貼圖

最終效果

代碼包括主程序源文件mainApp.cpp、頂點着色器shader.vs、片元着色器shader.fs

mainApp.cpp如下

#include <stdio.h>
#include <string.h> 
#include <iostream>
#include <fstream> 
#include <sstream>
#include <GL/glew.h>  
#include <GL/freeglut.h>   
#include <opencv2/core/core.hpp>  
#include <opencv2/highgui/highgui.hpp>  
#include <opencv2/imgproc/imgproc.hpp>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp> 

using namespace std; 
using namespace cv;
using namespace glm;

//shader文件
const char* vsShaderName = "shader.vs";//頂點着色器
const char* fsShaderName = "shader.fs";//片元着色器

GLuint VBO;//頂點緩沖對象
GLuint IBO;//索引緩沖對象
GLuint UVBO;//uv緩沖對象
GLuint TexBO;//貼圖對象
static  GLfloat *vertices;
static unsigned int *indices;
static  GLfloat *uvs;

GLuint ShaderProgram;
GLuint MatrixID;
GLuint TextureID;

int windowWidth = 800;
int windowHeight=800;
int imgWidth;
int imgHeihgt;
float verticeScale = 0.1f;
float ZScale = 5.0f;
//相機參數
glm::mat4 ViewMatrix;//視圖矩陣
glm::mat4 ProjectionMatrix; //投影矩陣
glm::mat4 MVP;//模型視圖矩陣
glm::mat4 ModelMatrix;//模型矩陣
glm::vec3 position = glm::vec3(5, 5, 5); //相機位置
float horizontalAngle = 3.14f; 
float verticalAngle = 0.0f; 
float initialFoV = 45.0f; //相機視場角
float speed = 0.05f; //平移速度
float mouseSpeed = 0.005f;
int mouseX, mouseY;//鼠標位置 窗口坐標


// 傳遞鍵盤事件
static void SpecialKeyboardCB(int Key, int x, int y)
{
	glm::vec3 direction(
		cos(verticalAngle) * sin(horizontalAngle),
		sin(verticalAngle),
		cos(verticalAngle) * cos(horizontalAngle)
	);
	glm::vec3 right = glm::vec3(
		sin(horizontalAngle - 3.14f / 2.0f),
		0,
		cos(horizontalAngle - 3.14f / 2.0f)
	);
	glm::vec3 up = glm::cross(right, direction);

	switch (Key) { 
	case GLUT_KEY_UP:
		position += direction  * speed;
		fprintf(stderr, "up key\n");
		break;
	case GLUT_KEY_RIGHT:
		position += right  * speed;
		fprintf(stderr, "right key\n");
		break;
	case GLUT_KEY_DOWN:
		position -= direction  * speed;
		fprintf(stderr, "down key\n");
		break;
	case GLUT_KEY_LEFT:
		position -= right  * speed;
		fprintf(stderr, "left key\n");
		break;
	case GLUT_KEY_F4:
		exit(1);
	default:
		fprintf(stderr, "Unimplemented GLUT key\n");
		//exit(1); 
	}

	float FoV = initialFoV;
	ProjectionMatrix = glm::perspective(glm::radians(FoV), 4.0f / 3.0f, 0.1f, 100.0f);
	ViewMatrix = glm::lookAt(
		position,          
		position + direction, 
		up                
	);
	ModelMatrix = glm::mat4(1.0);
	MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;  
	glutPostRedisplay();//設置窗口重繪
} 
//傳遞鼠標事件
static void PassiveMouseCB(int x, int y)
{  
	horizontalAngle += mouseSpeed * float(x-mouseX);
	verticalAngle += mouseSpeed * float(y-mouseY);
	mouseX = x;
	mouseY = y;
	SpecialKeyboardCB(0,0,0);
}

//渲染回調函數 
void RenderScenceCB() { 
	// 清空顏色緩存 
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	//傳遞mvp
	glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);   
	//傳遞頂點、索引、UV
	glEnableVertexAttribArray(0); //開啟頂點屬性
	glBindBuffer(GL_ARRAY_BUFFER, VBO); //綁定GL_ARRAY_BUFFER緩沖器 
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0); //告訴管線怎樣解析bufer中的數據  
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IBO);
	glEnableVertexAttribArray(1);
	glBindBuffer(GL_ARRAY_BUFFER, UVBO); 
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, 0);   
	//傳遞貼圖紋理
	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, TexBO);
	glUniform1i(TextureID, 0);  
	//繪制
	glDrawElements(GL_TRIANGLES, (imgWidth - 1)*(imgHeihgt - 1) * 6*4, GL_UNSIGNED_SHORT, 0); 
	glDisableVertexAttribArray(0);
	glDisableVertexAttribArray(1);
	 //交換前后緩存
	glutSwapBuffers();
} 

//創建頂點
static void CreateVertexBuffer()
{   
	//讀取圖片
	Mat img = imread("T2.png"); 
	int imgType = img.type();
#pragma region  灰度圖信息
	//  C1  C2 	C3 	C4
	//CV_8U 	0 	8 	16 	24
	//CV_8S 	1 	9 	17 	25
	//CV_16U 	2 	10 	18 	26
	//CV_16S 	3 	11 	19 	27
	//CV_32S 	4 	12 	20 	28
	//CV_32F 	5 	13 	21 	29
	//CV_64F 	6 	14 	22 	30 
	//fprintf(stderr, "Gray img type %d\n", imgType);  //16 即是CV_8UC3
	//imshow("grayImgTestShow",img); 
#pragma endregion  
	Mat resImg = Mat(img.rows, img.cols, imgType);
	resize(img, resImg, resImg.size(), 0, 0, INTER_LINEAR);
	Mat gImg = Mat(img.rows,img.cols,CV_8UC1); //灰度圖
	cv::cvtColor(resImg, gImg, CV_BGR2GRAY);//bgr轉灰度
	imgWidth = resImg.rows;
	imgHeihgt = resImg.cols; 
	//fprintf(stderr,"image gray type %d",resImg.type());
	vertices = new GLfloat[imgWidth*imgHeihgt*3];
	int k = 0; 
	for (int i = 0; i < imgWidth; i++)
	{
		for (int j = 0; j < imgHeihgt; j++)
		{
			vertices[k++] = verticeScale* (float)i;
			vertices[k++] = verticeScale*(float)j;  
			int c = (int)gImg.at<uchar>(i, j);
			//fprintf(stderr,"gray color %d  %d %d",i,j ,(int)gImg.at<uchar>(i, j));
			vertices[k++] = ZScale*(float)c / 255.0f;
		}
	}      
	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, imgWidth*imgHeihgt * 3*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
}
//創建索引
static void CreateIndexBuffer()
{ 
	indices = new unsigned int[(imgWidth-1)*(imgHeihgt-1) * 6];
	int k = 0; 

	for (int i = 0; i < imgWidth - 1; i++)
	{
		for (int j = 0; j < imgHeihgt - 1; j++)
		{
			indices[k++] = i*imgHeihgt + j;
			indices[k++] = i*imgHeihgt + j + 1;
			indices[k++] = i*imgHeihgt + j + imgHeihgt;
			indices[k++] = i*imgHeihgt + j + imgHeihgt;
			indices[k++] = i*imgHeihgt + j + 1;
			indices[k++] = i*imgHeihgt + j + imgHeihgt + 1;
		}
	}
	glGenBuffers(1, &IBO);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (imgWidth - 1)*(imgHeihgt - 1) * 6*sizeof(unsigned int), indices, GL_STATIC_DRAW);

 
}
//創建uv
static void CreateUVBuffer()
{
	uvs=new  GLfloat[imgWidth*imgHeihgt * 2];
	int k = 0;
	for (int i = 0; i < imgWidth; i++)
	{
		for (int j = 0; j < imgHeihgt; j++)
		{
			uvs[k++] = (float)i / (float)(imgWidth);
			uvs[k++] = (float)j / (float)(imgHeihgt);  
		}
	} 
	glGenBuffers(1, &UVBO);
	glBindBuffer(GL_ARRAY_BUFFER, UVBO);
	glBufferData(GL_ARRAY_BUFFER, imgWidth*imgHeihgt * 2 * sizeof(GLfloat), uvs, GL_STATIC_DRAW); 
}
 
//創建貼圖
static void CreateTexture()
{   
	Mat img = imread("grass.jpg");
	Mat resImg = Mat(256, 256, img.type());
	resize(img, resImg, resImg.size(), 0, 0, INTER_LINEAR);
	cv::cvtColor(resImg, resImg, CV_BGR2RGB);
	glGenTextures(1, &TexBO);
	glBindTexture(GL_TEXTURE_2D, TexBO); 
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, resImg.data);//設定紋理 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);//重復紋理
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);//濾波
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
	glGenerateMipmap(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, 0);   
	TextureID = glGetUniformLocation(ShaderProgram, "myTexture");  
}
// 使用shader文本編譯shader對象，並綁定shader到着色器程序中
static void AddShader(GLuint ShaderProgram, const char* pShaderText, GLenum ShaderType)
{
	// 根據shader類型參數定義兩個shader對象
	GLuint ShaderObj = glCreateShader(ShaderType);
	// 檢查是否定義成功
	if (ShaderObj == 0) {
		fprintf(stderr, "Error creating shader type %d\n", ShaderType);
		exit(0);
	}  
	// 定義shader的代碼源
	const GLchar* p[1];
	p[0] = pShaderText;
	GLint Lengths[1];
	Lengths[0] = strlen(pShaderText);
	glShaderSource(ShaderObj, 1, p, Lengths);
	glCompileShader(ShaderObj);// 編譯shader對象 
	 // 檢查和shader相關的錯誤
	GLint success;
	glGetShaderiv(ShaderObj, GL_COMPILE_STATUS, &success);
	if (!success) {
		GLchar InfoLog[1024];
		glGetShaderInfoLog(ShaderObj, 1024, NULL, InfoLog);
		fprintf(stderr, "Error compiling shader type %d: '%s'\n", ShaderType, InfoLog);
		exit(1);
	} 
	// 將編譯好的shader對象綁定到program object程序對象上
	glAttachShader(ShaderProgram, ShaderObj);
}

// 編譯着色器函數
static void CompileShaders()
{
	// 創建着色器程序
	ShaderProgram = glCreateProgram();
	// 檢查是否創建成功
	if (ShaderProgram == 0) {
		fprintf(stderr, "Error creating shader program\n");
		exit(1);
	}
	// 存儲着色器文本的字符串
	string vs, fs;
	// 分別讀取着色器文件中的文本到字符串
	std::ifstream VertexShaderStream(vsShaderName, std::ios::in);
	if (VertexShaderStream.is_open()) {
		std::stringstream sstr;
		sstr << VertexShaderStream.rdbuf();
		vs = sstr.str();
		VertexShaderStream.close();
	}
	else {
		printf("Error to open %s\n", vsShaderName);
		getchar(); 
		exit(0);
	} 
	std::ifstream FragmentShaderStream(fsShaderName, std::ios::in);
	if (FragmentShaderStream.is_open()) {
		std::stringstream sstr;
		sstr << FragmentShaderStream.rdbuf();
		fs = sstr.str();
		FragmentShaderStream.close();
	}

	// 添加頂點着色器和片段着色器
	AddShader(ShaderProgram, vs.c_str(), GL_VERTEX_SHADER);
	AddShader(ShaderProgram, fs.c_str(), GL_FRAGMENT_SHADER); 
	// 鏈接shader着色器程序，並檢查程序相關錯誤
	GLint Success = 0;
	GLchar ErrorLog[1024] = { 0 };
	glLinkProgram(ShaderProgram);
	glGetProgramiv(ShaderProgram, GL_LINK_STATUS, &Success);
	if (Success == 0) {
		glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
		fprintf(stderr, "Error linking shader program: '%s'\n", ErrorLog);
		exit(1);
	} 
	// 檢查驗證在當前的管線狀態程序是否可以被執行
	glValidateProgram(ShaderProgram);
	glGetProgramiv(ShaderProgram, GL_VALIDATE_STATUS, &Success);
	if (!Success) {
		glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
		fprintf(stderr, "Invalid shader program: '%s'\n", ErrorLog);
		exit(1);
	} 
	// 設置到管線聲明中來使用上面成功建立的shader程序
	glUseProgram(ShaderProgram);
    MatrixID = glGetUniformLocation(ShaderProgram, "gWVP");
}

int main(int argc, char ** argv) { 
	// 初始化GLUT
	glutInit(&argc, argv); 
	// 顯示模式：雙緩沖、RGBA
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA); 
	// 窗口設置
	glutInitWindowSize(windowWidth, windowHeight);      // 窗口尺寸
	glutInitWindowPosition(100, 100);  // 窗口位置
	glutCreateWindow("terrainTest1");   // 窗口標題 
								 
	GLenum res = glewInit();
	if (res != GLEW_OK) {
		fprintf(stderr, "Error: '%s'\n", glewGetErrorString(res));
		return 1;
	}

	// 開始渲染
	glutDisplayFunc(RenderScenceCB); 
	// 注冊鍵盤事件
	glutSpecialFunc(SpecialKeyboardCB);
	//注冊鼠標事件
	glutPassiveMotionFunc(PassiveMouseCB);
	mouseX = windowWidth / 2;
	mouseY = windowHeight / 2;
	// 緩存清空后的顏色值
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f); 
	//創建頂點
	CreateVertexBuffer();
	//創建索引
	CreateIndexBuffer();
	//創建uv
	CreateUVBuffer();
	//創建貼圖
	CreateTexture();
	// 編譯着色器
	CompileShaders();   
	//開啟深度測試
	glEnable(GL_DEPTH_TEST);
	// 通知開始GLUT的內部循環
	glutMainLoop();   
	delete vertices;
	return 0;
}

shader.vs 如下

#version 330 
layout (location = 0) in vec3 Position;
layout(location = 1) in vec2 vertexUV; 
// WVP標准
uniform mat4 gWVP; 
out vec2 UV; 
void main()
{
    gl_Position = gWVP * vec4(Position, 1.0);
    UV = vertexUV;
}

shader.fs如下

#version 330 
in vec2 UV; 
out vec3 FragColor; 
uniform sampler2D myTexture; 
void main()
{
    FragColor = texture( myTexture, UV ).rgb;  
}

參考鏈接

http://www.opengl-tutorial.org/

http://ogldev.atspace.co.uk/

https://learnopengl-cn.github.io/

本文鏈接

https://www.cnblogs.com/gucheng/p/10125162.html