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使用ASSIMP和OpenGL加载3D模型时纹理错误

c++openglglut
7

我正在尝试修改包含在ASSIMP的示例代码中的加载3D模型的样例代码，使用GLUT代替WGL。然而，我遇到了一个贴图问题，如下所示：

loaded 3d model

虽然它应该如下所示：

original 3d model

以下是绘制3D模型的代码：

void recursive_render (const struct aiScene *sc, const struct aiNode* nd, float scale){
unsigned int i;
unsigned int n=0, t;
struct aiMatrix4x4 m = nd->mTransformation;
m.Scaling(aiVector3D(scale, scale, scale), m);
// update transform
m.Transpose();
glPushMatrix();
glMultMatrixf((float*)&m);
// draw all meshes assigned to this node
for (; n < nd->mNumMeshes; ++n){
    const struct aiMesh* mesh = scene->mMeshes[nd->mMeshes[n]];
    apply_material(sc->mMaterials[mesh->mMaterialIndex]);
    if(mesh->mNormals == NULL){
        glDisable(GL_LIGHTING);
    }
    else {
        glEnable(GL_LIGHTING);
    }
    if(mesh->mColors[0] != NULL) {
        glEnable(GL_COLOR_MATERIAL);
    }
    else {
        glDisable(GL_COLOR_MATERIAL);
    }

    for (t = 0; t < mesh->mNumFaces; ++t) {
        const struct aiFace* face = &mesh->mFaces[t];
        GLenum face_mode;
        switch(face->mNumIndices) {
            case 1: face_mode = GL_POINTS; break;
            case 2: face_mode = GL_LINES; break;
            case 3: face_mode = GL_TRIANGLES; break;
            default: face_mode = GL_POLYGON; break;
        }
        glBegin(face_mode);
        for(i = 0; i < face->mNumIndices; i++){
            int vertexIndex = face->mIndices[i];    // get group index for current index
            if(mesh->mColors[0] != NULL)
                Color4f(&mesh->mColors[0][vertexIndex]); 
            if(mesh->mNormals != NULL)
                if(mesh->HasTextureCoords(0)){  
                    glTexCoord2f(mesh->mTextureCoords[0][vertexIndex].x, 1- mesh->mTextureCoords[0][vertexIndex].y);                    
                }
                glNormal3fv(&mesh->mNormals[vertexIndex].x);
                glVertex3fv(&mesh->mVertices[vertexIndex].x);
        }
        glEnd();
    }
}
// draw all children
for (n = 0; n < nd->mNumChildren; ++n)  {
    recursive_render(sc, nd->mChildren[n], scale);
}
glPopMatrix();

}

apply_material函数，几乎与ASSIMP提供的示例完全相同。

void apply_material(const struct aiMaterial *mtl)
{
float c[4];
GLenum fill_mode;
int ret1, ret2;
struct aiColor4D diffuse;
struct aiColor4D specular;
struct aiColor4D ambient;
struct aiColor4D emission;
float shininess, strength;
int two_sided;
int wireframe;
unsigned int max;   // changed: to unsigned
int texIndex = 0;
aiString texPath;   //contains filename of texture
if(AI_SUCCESS == mtl->GetTexture(aiTextureType_DIFFUSE, texIndex, &texPath))    {
    unsigned int texId = textureIdMap[texPath.data];
    glBindTexture(GL_TEXTURE_2D, texId);
}

set_float4(c, 0.8f, 0.8f, 0.8f, 1.0f);
if(AI_SUCCESS == aiGetMaterialColor(mtl, AI_MATKEY_COLOR_DIFFUSE, &diffuse))
    color4_to_float4(&diffuse, c);
glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, c);
set_float4(c, 0.2f, 0.2f, 0.2f, 1.0f);
if(AI_SUCCESS == aiGetMaterialColor(mtl, AI_MATKEY_COLOR_AMBIENT, &ambient))
    color4_to_float4(&ambient, c);
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, c);
set_float4(c, 0.0f, 0.0f, 0.0f, 1.0f);
if(AI_SUCCESS == aiGetMaterialColor(mtl, AI_MATKEY_COLOR_SPECULAR, &specular))
    color4_to_float4(&specular, c);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, c);
set_float4(c, 0.0f, 0.0f, 0.0f, 1.0f);
if(AI_SUCCESS == aiGetMaterialColor(mtl, AI_MATKEY_COLOR_EMISSIVE, &emission)) 
    color4_to_float4(&emission, c);
glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, c);

max = 1;
ret1 = aiGetMaterialFloatArray(mtl, AI_MATKEY_SHININESS, &shininess, &max);
max = 1;
ret2 = aiGetMaterialFloatArray(mtl, AI_MATKEY_SHININESS_STRENGTH, &strength, &max);
if((ret1 == AI_SUCCESS) && (ret2 == AI_SUCCESS))
    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, shininess * strength);
else {
    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 0.0f);
    set_float4(c, 0.0f, 0.0f, 0.0f, 0.0f);
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, c);
}

max = 1;
if(AI_SUCCESS == aiGetMaterialIntegerArray(mtl, AI_MATKEY_ENABLE_WIREFRAME, &wireframe, &max))
    fill_mode = wireframe ? GL_LINE : GL_FILL;
else
    fill_mode = GL_FILL;
glPolygonMode(GL_FRONT_AND_BACK, fill_mode);

max = 1;
if((AI_SUCCESS == aiGetMaterialIntegerArray(mtl, AI_MATKEY_TWOSIDED, &two_sided, &max)) && two_sided)
    glEnable(GL_CULL_FACE);
else
    glDisable(GL_CULL_FACE);
}

而且loadGLtextures函数，我不认为它与剔除有关。
int LoadGLTextures(const aiScene* scene) {
ILboolean success;
/* initialization of DevIL */
ilInit(); 
/* scan scene's materials for textures */
for (unsigned int m=0; m<scene->mNumMaterials; ++m) {
    int texIndex = 0;
    aiString path;  // filename
    aiReturn texFound = scene->mMaterials[m]->GetTexture(aiTextureType_DIFFUSE, texIndex, &path);
    while (texFound == AI_SUCCESS) {
        //fill map with textures, OpenGL image ids set to 0
        textureIdMap[path.data] = 0; 
        // more textures?
        texIndex++;
        texFound = scene->mMaterials[m]->GetTexture(aiTextureType_DIFFUSE, texIndex, &path);
    }
}

int numTextures = textureIdMap.size();
/* create and fill array with DevIL texture ids */
ILuint* imageIds = new ILuint[numTextures];
ilGenImages(numTextures, imageIds); 
/* create and fill array with GL texture ids */
GLuint* textureIds = new GLuint[numTextures];
glGenTextures(numTextures, textureIds); /* Texture name generation */

/* get iterator */
std::map<std::string, GLuint>::iterator itr = textureIdMap.begin();
printf("TextureIDMap Begin %i\n", textureIdMap.begin());
int i=0;
for (; itr != textureIdMap.end(); ++i, ++itr) {
    //save IL image ID
    std::string filename = (*itr).first;  // get filename
    (*itr).second = textureIds[i];    // save texture id for filename in map
    printf("Texture loaded: %s\n",filename.c_str());
    printf("Texture ID Map End: %i\n",textureIdMap.end());
    ilBindImage(imageIds[i]); /* Binding of DevIL image name */
    ilEnable(IL_ORIGIN_SET);
    ilOriginFunc(IL_ORIGIN_LOWER_LEFT); 
    success = ilLoadImage((ILstring)filename.c_str());

    if (success) {
        /* Convert image to RGBA */
        ilConvertImage(IL_RGBA, IL_UNSIGNED_BYTE); 

        /* Create and load textures to OpenGL */
        glBindTexture(GL_TEXTURE_2D, textureIds[i]); 
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ilGetInteger(IL_IMAGE_WIDTH),
            ilGetInteger(IL_IMAGE_HEIGHT), 0, GL_RGBA, GL_UNSIGNED_BYTE,
            ilGetData()); 
    }
    else 
        printf("Couldn't load Image: %s\n", filename.c_str());
}
/* Because we have already copied image data into texture data  we can release memory used by image. */
ilDeleteImages(numTextures, imageIds); 
//Cleanup
delete [] imageIds;
delete [] textureIds;
//return success;
return true;
}

Lighthouse 3D提供了一个示例，用于实现此操作，但目前我无法将GLSL和VAO应用到我的程序中。有什么解决方案吗？提前致谢。
我可能错了，但问题可能不在纹理上，而是在材质上。 - Salvatore Previti
你有任何想法是什么导致了这个材料的问题吗？谢谢。 - fatarms
我尝试了Lighthouse 3D的教程，但是我无法加载模型。 - user868935
4个回答
9

我已找到解决方法。我使用以下代码更改了在recursive_render函数中访问纹理的方式：

glTexCoord2f(mesh->mTextureCoords[0][vertexIndex].x,  mesh->mTextureCoords[0][vertexIndex].y);

替代：

glTexCoord2f(mesh->mTextureCoords[0][vertexIndex].x,  1-mesh->mTextureCoords[0][vertexIndex].y);
我正在使用Assimp和GLSL，我提供给Assimp的模型中的UV纹理仅在我使用glTexCoord2f(mesh->mTextureCoords[0][vertexIndex].x, 1-(mesh->mTextureCoords[0][vertexIndex].y));时才起作用。否则，我会遇到奇怪的纹理行为。我认为只有少数模型需要1-y。 - 2am
2
这不是贴图的问题。你的问题来自于背面剔除（至少看起来是这样，因为你可以看到鸭子的内部）。要么你的多边形顺序错了，要么你的背面剔除设置不正确。如果你发布设置背面剔除的代码，我们就能看到问题出在哪里。
还有可能是你的一些法线朝向内部（这也可能是由于多边形顺序导致的）。这就解释了为什么你鸭子的嘴巴是漆黑的。
感谢您的回答。启用/禁用剔除是在“apply_material”函数的末尾设置的。我不确定问题是否与剔除有关，因为即使我已经禁用了剔除，纹理仍然无法正确加载（如果我有所误解，请指正）。我已经编辑了代码。 - fatarms
你尝试过完全禁用剔除吗？即删除if语句，只需放置glDisable(GL_CULL_FACE)。 - NickLH
1

我相信问题在于纹理沿Y轴被“翻转”了。这就是为什么你的“1-y”起作用。可以通过在加载时翻转纹理来解决这个问题。虽然我还不确定原因，因为今天才偶然发现了这个问题。

1

我不确定这是否有帮助，但你可以在导入模型时翻转UV坐标。

const aiScene* scene = importer.ReadFile(path, aiProcess_FlipUVs);
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