# opengl 学习 之 07 lesson

opengl 学习 之 07 lesson

简介

OBJ的使用

link

http://www.opengl-tutorial.org/uncategorized/2017/06/07/website-update/

TIPS

不同的obj有不同的格式

code

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <vector>

// Include GLEW
#include <GL/glew.h>

// Include GLFW
#include <GLFW/glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;

#include <common/shader.hpp>
#include <common/texture.hpp>
#include <common/controls.hpp>
#include <common/objloader.hpp>

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW
" );
		getchar();
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Tutorial 07 - Model Loading", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.
" );
		getchar();
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW
");
		getchar();
		glfwTerminate();
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    // Hide the mouse and enable unlimited mouvement
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    
    // Set the mouse at the center of the screen
    glfwPollEvents();
    glfwSetCursorPos(window, 1024/2, 768/2);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	glDepthFunc(GL_LESS); 

	// Cull triangles which normal is not towards the camera
	glEnable(GL_CULL_FACE);

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "TextureFragmentShader.fragmentshader" );

	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");

	// Load the texture
	GLuint Texture = loadDDS("uvmap.DDS");
	
	// Get a handle for our "myTextureSampler" uniform
	GLuint TextureID  = glGetUniformLocation(programID, "myTextureSampler");

	// Read our .obj file
	std::vector<glm::vec3> vertices;
	std::vector<glm::vec2> uvs;
	std::vector<glm::vec3> normals; // Won't be used at the moment.
	bool res = loadOBJ("cube.obj", vertices, uvs, normals);

	// Load it into a VBO

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec3), &vertices[0], GL_STATIC_DRAW);

	GLuint uvbuffer;
	glGenBuffers(1, &uvbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
	glBufferData(GL_ARRAY_BUFFER, uvs.size() * sizeof(glm::vec2), &uvs[0], GL_STATIC_DRAW);

	do{

		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// Compute the MVP matrix from keyboard and mouse input
		computeMatricesFromInputs();
		glm::mat4 ProjectionMatrix = getProjectionMatrix();
		glm::mat4 ViewMatrix = getViewMatrix();
		glm::mat4 ModelMatrix = glm::mat4(1.0);
		glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;

		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

		// Bind our texture in Texture Unit 0
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, Texture);
		// Set our "myTextureSampler" sampler to use Texture Unit 0
		glUniform1i(TextureID, 0);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// 2nd attribute buffer : UVs
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
		glVertexAttribPointer(
			1,                                // attribute
			2,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, vertices.size() );

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

	// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &uvbuffer);
	glDeleteProgram(programID);
	glDeleteTextures(1, &Texture);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}

# Blender3D v249 OBJ File: untitled.blend
# www.blender3d.org
mtllib cube.mtl
v 1.000000 -1.000000 -1.000000
v 1.000000 -1.000000 1.000000
v -1.000000 -1.000000 1.000000
v -1.000000 -1.000000 -1.000000
v 1.000000 1.000000 -1.000000
v 0.999999 1.000000 1.000001
v -1.000000 1.000000 1.000000
v -1.000000 1.000000 -1.000000
vt 0.748573 0.750412
vt 0.749279 0.501284
vt 0.999110 0.501077
vt 0.999455 0.750380
vt 0.250471 0.500702
vt 0.249682 0.749677
vt 0.001085 0.750380
vt 0.001517 0.499994
vt 0.499422 0.500239
vt 0.500149 0.750166
vt 0.748355 0.998230
vt 0.500193 0.998728
vt 0.498993 0.250415
vt 0.748953 0.250920
vn 0.000000 0.000000 -1.000000
vn -1.000000 -0.000000 -0.000000
vn -0.000000 -0.000000 1.000000
vn -0.000001 0.000000 1.000000
vn 1.000000 -0.000000 0.000000
vn 1.000000 0.000000 0.000001
vn 0.000000 1.000000 -0.000000
vn -0.000000 -1.000000 0.000000
usemtl Material_ray.png
s off
f 5/1/1 1/2/1 4/3/1
f 5/1/1 4/3/1 8/4/1
f 3/5/2 7/6/2 8/7/2
f 3/5/2 8/7/2 4/8/2
f 2/9/3 6/10/3 3/5/3
f 6/10/4 7/6/4 3/5/4
f 1/2/5 5/1/5 2/9/5
f 5/1/6 6/10/6 2/9/6
f 5/1/7 8/11/7 6/10/7
f 8/11/7 7/12/7 6/10/7
f 1/2/8 2/9/8 3/13/8
f 1/2/8 3/13/8 4/14/8

#version 330 core

// Input vertex data, different for all executions of this shader.
layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec2 vertexUV;

// Output data ; will be interpolated for each fragment.
out vec2 UV;

// Values that stay constant for the whole mesh.
uniform mat4 MVP;

void main(){

	// Output position of the vertex, in clip space : MVP * position
	gl_Position =  MVP * vec4(vertexPosition_modelspace,1);
	
	// UV of the vertex. No special space for this one.
	UV = vertexUV;
}

#version 330 core

// Interpolated values from the vertex shaders
in vec2 UV;

// Ouput data
out vec3 color;

// Values that stay constant for the whole mesh.
uniform sampler2D myTextureSampler;

void main(){

	// Output color = color of the texture at the specified UV
	color = texture( myTextureSampler, UV ).rgb;
}

#include <vector>
#include <stdio.h>
#include <string>
#include <cstring>

#include <glm/glm.hpp>

#include "objloader.hpp"

// Very, VERY simple OBJ loader.
// Here is a short list of features a real function would provide : 
// - Binary files. Reading a model should be just a few memcpy's away, not parsing a file at runtime. In short : OBJ is not very great.
// - Animations & bones (includes bones weights)
// - Multiple UVs
// - All attributes should be optional, not "forced"
// - More stable. Change a line in the OBJ file and it crashes.
// - More secure. Change another line and you can inject code.
// - Loading from memory, stream, etc

bool loadOBJ(
	const char * path, 
	std::vector<glm::vec3> & out_vertices, 
	std::vector<glm::vec2> & out_uvs,
	std::vector<glm::vec3> & out_normals
){
	printf("Loading OBJ file %s...
", path);

	std::vector<unsigned int> vertexIndices, uvIndices, normalIndices;
	std::vector<glm::vec3> temp_vertices; 
	std::vector<glm::vec2> temp_uvs;
	std::vector<glm::vec3> temp_normals;


	FILE * file = fopen(path, "r");
	if( file == NULL ){
		printf("Impossible to open the file ! Are you in the right path ? See Tutorial 1 for details
");
		getchar();
		return false;
	}

	while( 1 ){

		char lineHeader[128];
		// read the first word of the line
		int res = fscanf(file, "%s", lineHeader);
		if (res == EOF)
			break; // EOF = End Of File. Quit the loop.

		// else : parse lineHeader
		
		if ( strcmp( lineHeader, "v" ) == 0 ){
			glm::vec3 vertex;
			fscanf(file, "%f %f %f
", &vertex.x, &vertex.y, &vertex.z );
			temp_vertices.push_back(vertex);
		}else if ( strcmp( lineHeader, "vt" ) == 0 ){
			glm::vec2 uv;
			fscanf(file, "%f %f
", &uv.x, &uv.y );
			uv.y = -uv.y; // Invert V coordinate since we will only use DDS texture, which are inverted. Remove if you want to use TGA or BMP loaders.
			temp_uvs.push_back(uv);
		}else if ( strcmp( lineHeader, "vn" ) == 0 ){
			glm::vec3 normal;
			fscanf(file, "%f %f %f
", &normal.x, &normal.y, &normal.z );
			temp_normals.push_back(normal);
		}else if ( strcmp( lineHeader, "f" ) == 0 ){
			std::string vertex1, vertex2, vertex3;
			unsigned int vertexIndex[3], uvIndex[3], normalIndex[3];
			int matches = fscanf(file, "%d/%d/%d %d/%d/%d %d/%d/%d
", &vertexIndex[0], &uvIndex[0], &normalIndex[0], &vertexIndex[1], &uvIndex[1], &normalIndex[1], &vertexIndex[2], &uvIndex[2], &normalIndex[2] );
			if (matches != 9){
				printf("File can't be read by our simple parser :-( Try exporting with other options
");
				fclose(file);
				return false;
			}
			vertexIndices.push_back(vertexIndex[0]);
			vertexIndices.push_back(vertexIndex[1]);
			vertexIndices.push_back(vertexIndex[2]);
			uvIndices    .push_back(uvIndex[0]);
			uvIndices    .push_back(uvIndex[1]);
			uvIndices    .push_back(uvIndex[2]);
			normalIndices.push_back(normalIndex[0]);
			normalIndices.push_back(normalIndex[1]);
			normalIndices.push_back(normalIndex[2]);
		}else{
			// Probably a comment, eat up the rest of the line
			char stupidBuffer[1000];
			fgets(stupidBuffer, 1000, file);
		}

	}

	// For each vertex of each triangle
	for( unsigned int i=0; i<vertexIndices.size(); i++ ){

		// Get the indices of its attributes
		unsigned int vertexIndex = vertexIndices[i];
		unsigned int uvIndex = uvIndices[i];
		unsigned int normalIndex = normalIndices[i];
		
		// Get the attributes thanks to the index
		glm::vec3 vertex = temp_vertices[ vertexIndex-1 ];
		glm::vec2 uv = temp_uvs[ uvIndex-1 ];
		glm::vec3 normal = temp_normals[ normalIndex-1 ];
		
		// Put the attributes in buffers
		out_vertices.push_back(vertex);
		out_uvs     .push_back(uv);
		out_normals .push_back(normal);
	
	}
	fclose(file);
	return true;
}


#ifdef USE_ASSIMP // don't use this #define, it's only for me (it AssImp fails to compile on your machine, at least all the other tutorials still work)

// Include AssImp
#include <assimp/Importer.hpp>      // C++ importer interface
#include <assimp/scene.h>           // Output data structure
#include <assimp/postprocess.h>     // Post processing flags

bool loadAssImp(
	const char * path, 
	std::vector<unsigned short> & indices,
	std::vector<glm::vec3> & vertices,
	std::vector<glm::vec2> & uvs,
	std::vector<glm::vec3> & normals
){

	Assimp::Importer importer;

	const aiScene* scene = importer.ReadFile(path, 0/*aiProcess_JoinIdenticalVertices | aiProcess_SortByPType*/);
	if( !scene) {
		fprintf( stderr, importer.GetErrorString());
		getchar();
		return false;
	}
	const aiMesh* mesh = scene->mMeshes[0]; // In this simple example code we always use the 1rst mesh (in OBJ files there is often only one anyway)

	// Fill vertices positions
	vertices.reserve(mesh->mNumVertices);
	for(unsigned int i=0; i<mesh->mNumVertices; i++){
		aiVector3D pos = mesh->mVertices[i];
		vertices.push_back(glm::vec3(pos.x, pos.y, pos.z));
	}

	// Fill vertices texture coordinates
	uvs.reserve(mesh->mNumVertices);
	for(unsigned int i=0; i<mesh->mNumVertices; i++){
		aiVector3D UVW = mesh->mTextureCoords[0][i]; // Assume only 1 set of UV coords; AssImp supports 8 UV sets.
		uvs.push_back(glm::vec2(UVW.x, UVW.y));
	}

	// Fill vertices normals
	normals.reserve(mesh->mNumVertices);
	for(unsigned int i=0; i<mesh->mNumVertices; i++){
		aiVector3D n = mesh->mNormals[i];
		normals.push_back(glm::vec3(n.x, n.y, n.z));
	}


	// Fill face indices
	indices.reserve(3*mesh->mNumFaces);
	for (unsigned int i=0; i<mesh->mNumFaces; i++){
		// Assume the model has only triangles.
		indices.push_back(mesh->mFaces[i].mIndices[0]);
		indices.push_back(mesh->mFaces[i].mIndices[1]);
		indices.push_back(mesh->mFaces[i].mIndices[2]);
	}
	
	// The "scene" pointer will be deleted automatically by "importer"
	return true;
}

#endif