3

I am trying to integrate the Assimp loader to my framework. Everything is rendered fine, but in this spider model I'm rendering, its fangs are not being drawn as expected (see following picture).

spider

Below is the relevant code snippet:

//Storing the Indices
for (unsigned int t = 0; t < mesh->mNumFaces; ++t) {
    aiFace* face = &mesh->mFaces[t];
    memcpy(&faceArray[index], face->mIndices, 3*sizeof(unsigned int));
    index += 3;
}

//Storing the Vertices
for (unsigned int t = 0; t < mesh->mNumVertices; ++t) {
    aiVector3D vertex ;
    if (mesh->HasPositions()) {
        vertex = mesh->mVertices[t];
        memcpy(&vertexArray[index], &vertex,3*sizeof(float));
    }
    index += 3;          
}

//Render module
void model::helperDraw(GLuint vertexBufferID, GLuint indexBufferID, GLuint textureID)
{
    GLint indexSize;
    glBindBuffer(GL_ARRAY_BUFFER,vertexBufferID);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,indexBufferID);
    glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &indexSize);
    glBindTexture( GL_TEXTURE_2D, textureID);
    glDrawElements(GL_TRIANGLES, indexSize/sizeof(GLuint), GL_UNSIGNED_INT, 0);
}

What could be wrong with my code?

glampert
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proton
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    Are you sure that all your faces are triangles? In a general OBJ file, faces can be polygons with any number of vertices. – Reto Koradi Jul 06 '14 at 21:54
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    Yes, indeed, like @RetoKoradi said, the faces might actually be quads or tri-strips. Pass the `aiProcess_Triangulate` flag to assimp when loading the model to make sure all faces are triangulated. – glampert Jul 07 '14 at 02:24
  • Earlier the flag was aiProcessPreset_TargetRealtime_Quality changed the same to aiProcess_Triangulate and it worked – proton Jul 07 '14 at 17:04

1 Answers1

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There is nothing obviously wrong with your code. One possible cause for these rendering artefacts is that the OBJ model you load has some faces that are triangles an some faces that are not. You are rendering everything as GL_TRIANGLES, but the OBJ format can specify faces as quads, triangle-strips, triangles and even other more exotic things like patches.

Assimp has a mesh triangulation facility that can make your life a lot easier when dealing with these multi-format mesh files, such as the OBJ. Try passing the flag aiProcess_Triangulate to the load method of the importer or even to the post-processing method if you do post-processing as a separate step. This is likely to fix the issue.

glampert
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  • I am trying to use the tutorial [http://ogldev.atspace.co.uk/www/tutorial38/tutorial38.html] and add animation to my code. Could not figure out how to find the 4 bones + weights, guiding/related to a particular vertex in the animation. – proton Jul 31 '14 at 11:39
  • @ppu, I think asking a "real" question is in order, in case you need further help. Also, you might want to try the GameDev section: http://gamedev.stackexchange.com/ – glampert Jul 31 '14 at 18:37
  • "real" question [http://stackoverflow.com/questions/25063274/assimp-skeletal-animation-bones-associated-with-a-vertex] – proton Aug 01 '14 at 07:03