OpenGL -- OBJ 模型加载

使用:

// Read our .obj file

std::vector vertices;

std::vector uvs;

std::vector normals;

bool res = loadOBJ(“suzanne.obj”, vertices, uvs, normals);

实现:

#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...\n", 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\n");
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\n", &vertex.x, &vertex.y, &vertex.z );
temp_vertices.push_back(vertex);
}
else if ( strcmp( lineHeader, "vt" ) == 0 )
{
glm::vec2 uv;
fscanf(file, "%f %f\n", &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\n", &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\n", &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\n");
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;
}