Issues glVertexAttribPointer last 2 parameters?
- by NoobScratcher
Introduction
Hello I will start out by explaining my setup, showing samples as I go along explaining the situation.
I'm using these tools:
OpenGL 3.3
GLSL 330
C++
Problem
The problem is when I render the wavefront obj 3d model it gives a very weird visual glitch the model was supposed to be a square but instead its a triangluated mess with parts of the vertexes pointing in a stretched direction in massive amounts towards the bottom left side of the frustum....
Explanation:
I'm using std::vectors to store my wavefront .obj model data using sscanf to get the floating point values into the structure members x,y,z and store them into the Points structure variable p;
int index = IndexAssigner(1, 1);
ifstream file (list[index].c_str() );
points.push_back(Point());
Point p;
int face[4];
while (!file.eof() ) {
char modelbuffer[10000];
file.getline(modelbuffer, 10000);
switch(modelbuffer[0]) {
case 'v' :
sscanf(modelbuffer, "v %f %f %f", &p.x, &p.y, &p.z);
points.push_back(p);
break;
case 'f':
sscanf(modelbuffer, "f %d %d %d %d", face, face+1, face+2, face+3 );
faces.push_back(face[0]);
faces.push_back(face[1]);
faces.push_back(face[2]);
faces.push_back(face[3]);
}
//Turn on FileReader aka "RENDER CODE"
FileReader = true;
}
then I render the Points vector using the .data() member of std::vectors to the frustum.
Other declarations:
int numfloats = 4;
float* point=reinterpret_cast<float*>(&points[0]);
int num_bytes=numfloats*sizeof(float);
Vector declarations:
struct Point {float x, y , z; };
std::vector<int>faces;
std::vector<Point>points;
Render code:
glGenBuffers(1, &vertexbuffer);
glGenTextures(1, &ModelTexture);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBindTexture(GL_TEXTURE_3D, ModelTexture);
glTexImage2D(GL_TEXTURE_2D, 0,GL_RGBA, ModelSurface->w, ModelSurface->h, 0, GL_BGR, GL_UNSIGNED_BYTE, ModelSurface->pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glBufferData(GL_ARRAY_BUFFER, sizeof(points), points.data(), GL_STATIC_DRAW);
glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE,num_bytes ,points.data());
glEnableVertexAttribArray(3);
//Translation Process
GLfloat TranslationMatrix[] = {
1.0, 0.0, 0.0, 0.0,
0.0, 1.0, 0.0, 0.0,
0.0, 0.0, 1.0, 1.0,
0.0, 0.0, 0.0, 1.0
};
//Send Translation Matrix up to the vertex shader
glUniformMatrix4fv(translation, 1, TRUE, TranslationMatrix);
glDrawElements( GL_QUADS, faces.size(), GL_UNSIGNED_INT, faces.data());
I tried looking at what was causing this and went through every function every parameter ,etc looked at the man pages.
Then found out that it could be my glVertexAttribPointer.
Here are the man pages for glVertexAttribPointer
http://www.opengl.org/sdk/docs/man/xhtml/glVertexAttribPointer.xml
The last 2 parameters is my problem
How do I write those 2 last parameters do I try putting the data from Points into it?.
glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE,num_bytes ,points.data());
How does it work with vectors?
Is it fast?*
if you can not be bothered too look at the man pages here is the scripts coming from the man pages directly.
Stride
Specifies the byte offset between consecutive generic vertex attributes. If stride is 0, the generic vertex attributes are understood to be tightly packed in the array. The initial value is 0.
Pointer
Specifies a pointer to the first component of the first generic vertex attribute in the array. The initial value is 0.
If you want my full source - http://ideone.com/fPfkg
Thanks Again if you do read this.
