为什么我的波前 obj 文件解析器不能正确排序顶点？

Question

解析法线和顶点仅正确渲染正面。这只是顶点，法线代码的工作方式相同：

for(i = 0; i < vertexsize; i += 3){
    verticesind[i] = verticesout[vertexindices[i] - 1];
    verticesind[i + 1] = verticesout[vertexindices[i + 1] - 1];
    verticesind[i + 2] = verticesout[vertexindices[i + 2] - 1];
    verticessize += sizeof(verticesind[i]) + sizeof(verticesind[i + 1]) + sizeof(vertices[i + 2]);
}

模型.obj：

# Blender v2.93.8 OBJ File: ''
# www.blender.org
o Cube
v 0.500000 0.500000 -0.500000
v 0.500000 -0.500000 -0.500000
v 0.500000 0.500000 0.500000
v 0.500000 -0.500000 0.500000
v -0.500000 0.500000 -0.500000
v -0.500000 -0.500000 -0.500000
v -0.500000 0.500000 0.500000
v -0.500000 -0.500000 0.500000
vt 0.875000 0.500000
vt 0.625000 0.750000
vt 0.625000 0.500000
vt 0.375000 1.000000
vt 0.375000 0.750000
vt 0.625000 0.000000
vt 0.375000 0.250000
vt 0.375000 0.000000
vt 0.375000 0.500000
vt 0.125000 0.750000
vt 0.125000 0.500000
vt 0.625000 0.250000
vt 0.875000 0.750000
vt 0.625000 1.000000
vn 0.0000 1.0000 0.0000
vn 0.0000 0.0000 1.0000
vn -1.0000 0.0000 0.0000
vn 0.0000 -1.0000 0.0000
vn 1.0000 0.0000 0.0000
vn 0.0000 0.0000 -1.0000
s off
f 5/1/1 3/2/1 1/3/1
f 3/2/2 8/4/2 4/5/2
f 7/6/3 6/7/3 8/8/3
f 2/9/4 8/10/4 6/11/4
f 1/3/5 4/5/5 2/9/5
f 5/12/6 2/9/6 6/7/6
f 5/1/1 7/13/1 3/2/1
f 3/2/2 7/14/2 8/4/2
f 7/6/3 5/12/3 6/7/3
f 2/9/4 4/5/4 8/10/4
f 1/3/5 3/2/5 4/5/5
f 5/12/6 1/3/6 2/9/6

顶部三角形之一应该是：

-0.5, 0.5, -0.5,
 0.5, 0.5,  0.5,
 0.5, 0.5, -0.5

一个完整的三角形，但它们变成了：

-0.5, -0.5, 0.5,
-0.5,  0.5, 0.5,
 0.5, -0.5, 0.5

我的功能：

int load_obj(const char* filename, float* vertices, float* texcoords, float* normals, unsigned int* vertexindexsize, unsigned int* texcoordindexsize, unsigned int* normalindexsize){
    FILE* file = fopen(filename, "r");
    char lineheader[128];
    int res;
    int i = 0;
    int f = 0;
    int d = 0;
    int g = 0;
    unsigned int vertexsize = 0;
    unsigned int texcoordsize = 0;
    unsigned int normalsize = 0;
    unsigned int verticessize = 0;
    unsigned int texturecoordsize = 0;
    unsigned int normalssize = 0;
    float verticesout[500];
    float texcoordsout[500];
    float normalsout[500];
    float verticesind[500];
    float texturecoordsind[500];
    float normalsind[500];
    unsigned int vertexindex[3];
    unsigned int texindex[3];
    unsigned int normalindex[3];
    vec3 vertex;
    vec2 texcoord;
    vec3 normal;
    int vertexindices[500];
    int texindices[500];
    int normalindices[500];
    if(file == NULL){
        printf("Failed to open file!\n");
        return 1;
    }
    while(1){
        res = fscanf(file, "%s", lineheader);
        if(res == EOF){
            break;
        }
        if(strcmp(lineheader, "v") == 0){
            fscanf(file, "%f %f %f\n", &vertex[0], &vertex[1], &vertex[2]);
            verticesout[i] = vertex[0];
            verticesout[i + 1] = vertex[1];
            verticesout[i + 2] = vertex[2];
            i += 3;
        }else if(strcmp(lineheader, "vt") == 0){
            fscanf(file, "%f %f\n", &texcoord[0], &texcoord[1]);
            texcoordsout[f] = texcoord[0];
            texcoordsout[f + 1] = texcoord[1];
            f += 2;
        }else if(strcmp(lineheader, "vn") == 0){
            fscanf(file, "%f %f %f\n", &normal[0], &normal[1], &normal[2]);
            normalsout[d] = normal[0];
            normalsout[d + 1] = normal[1];
            normalsout[d + 2] = normal[2];
            d += 3;
        }else if(strcmp(lineheader, "f") == 0){
            fscanf(file, "%d/%d/%d %d/%d/%d %d/%d/%d\n", &vertexindex[0], &texindex[0], &normalindex[0], &vertexindex[1], &texindex[1], &normalindex[1], &vertexindex[2], &texindex[2], &normalindex[2]);
            vertexindices[g] = vertexindex[0];
            vertexindices[g + 1] = vertexindex[1];
            vertexindices[g + 2] = vertexindex[2];
        vertexsize += 3;
            texindices[g] = texindex[0];
            texindices[g + 1] = texindex[1];
            texindices[g + 2] = texindex[2];
        texcoordsize += 3;
            normalindices[g] = normalindex[0];
            normalindices[g + 1] = normalindex[1];
            normalindices[g + 2] = normalindex[2];
        normalsize += 3;
            g += 3;
        }
    }
    for(i = 0; i < vertexsize; i += 3){
        verticesind[i] = verticesout[vertexindices[i] - 1];
        verticesind[i + 1] = verticesout[vertexindices[i + 1] - 1];
        verticesind[i + 2] = verticesout[vertexindices[i + 2] - 1];
        verticessize += sizeof(verticesind[i]) + sizeof(verticesind[i + 1]) + sizeof(vertices[i + 2]);
    }
    for(i = 0; i < texcoordsize; i++){
        texturecoordsind[i] = texcoordsout[texindices[i] - 1];
        texturecoordsize += sizeof(texturecoordsind[i]);
    }
    for(i = 0; i < normalsize; i += 3){
        normalsind[i] = normalsout[normalindices[i] - 1];
        normalsind[i + 1] = normalsout[normalindices[i + 1] - 1];
        normalsind[i + 2] = normalsout[normalindices[i + 2] - 1];
        normalssize += sizeof(normalsind[i]) + sizeof(normalsind[i + 1]) + sizeof(normalsind[i + 2]);
    }
    memcpy(vertices, verticesind, sizeof(verticesind));
    memcpy(texcoords, texturecoordsind, sizeof(texturecoordsind));
    memcpy(normals, normalsind, sizeof(normalsind));
    *vertexindexsize = verticessize;
    *texcoordindexsize = texturecoordsize;
    *normalindexsize = normalssize;
    return 0;
}

Answer 1

我稍微改变了函数，因为它没有正确使用索引：

for(i = 0; i < vertexsize; i++){
      verticesind[i * 3] = verticesout[(vertexindices[i] - 1) * 3];
      verticesind[i * 3 + 1] = verticesout[(vertexindices[i] - 1) * 3 + 1];
      verticesind[i * 3 + 2] = verticesout[(vertexindices[i] - 1) * 3 + 2];
      verticessize += sizeof(verticesind[i]) * 3;
}

现在它可以正确加载顶点和法线。