iOS GL ES exc_bad_access on glDrawElements - c++

Question

I'm trying to make a small application that loads and renders a model on iOS using assimp and GL ES. I've worked with OpenGL before but not GL ES; and never anything on iOS.
Currently I'm getting a EXC_BAD_ACCESS error upon calling glDrawElements; and I can't see what I'm doing wrong.
This is my Vertex type:
typedef struct {
float Position[3];
} Vertex;
And this is my Mesh type:
class Mesh {
public:
Vertex* vertices;
GLuint verticesCount;
GLubyte* indices;
GLuint indicesCount;
std::vector<Texture> textures;
GLuint vertexBuffer, indexBuffer;
Mesh(Vertex* vertices, GLubyte* indices, std::vector<Texture> textures);
};
I am pretty confident that I'm loading the models correctly through assimp as I've done it before and lifted this code from another project. So I'm using that data to pass into Mesh constructor and I am populating the VBO's using this:
glGenBuffers(1, &this->vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, this->vertexBuffer);
int sizeOfVerts = sizeof(Vertex) * this->verticesCount;
std::cout << "Size of verts in bytes " << unsigned(sizeOfVerts) << std::endl;
glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)sizeOfVerts, &this->vertices[0], GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glGenBuffers(1, &this->indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this->indexBuffer);
int sizeOfInd = sizeof(GLubyte) * this->indicesCount;
std::cout << "Size of inds in bytes " << unsigned(sizeOfInd) << std::endl;
glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)sizeOfInd, &this->indices[0], GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
With the projection and view model matricies already set up in a pre-render function I am then calling this to render my meshes:
- (void)renderMesh:(Mesh*)mesh
{
glBindBuffer(GL_ARRAY_BUFFER, mesh->vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh->indexBuffer);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
int meshSize = mesh->indicesCount;
glDrawElements(GL_TRIANGLES, meshSize, GL_UNSIGNED_BYTE, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}
With _positionSlot being an attrib location in my shader. I know my shader works as I have already used it to draw boring squared and such - so the error is definitely in the above code - somewhere.
Thanks in advance guys, I'll make sure I both upvote and accept :)

Answer 1

The reason this was happening is because I was using GLubyte for the Indices type; which is too small for my high poly model. Not sure why the error manifested itself with this error message though; on other platforms the same code would render a junk model. Perhaps iOS specific? Hopefully this can help someone else.