CODEWITHSUNDEEP
iosopengl-es
Jakob
Jakob

Reputation: 982

OpenGL ES - updating the vertex array, adding/removing vertices

I want to implement functionality so that i can add/remove vertices to/from a vertex array during runtime. Is there a common way of doing this?

The recommended format for vertex data seems to be C arrays of structs, so i've tried the following. Keep a pointer to an array of Vertex structs as property:

@property Vertex *vertices;

and then make a new array and copy the data over

- (void) addVertex:(Vertex)newVertex
{
    int numberOfVertices = sizeof(vertices) / sizeof(Vertex);
    Vertex newArray[numberOfVertices + 1];

    for (int i = 0; i < numberOfVertices; i++) 
        newArray[i] = vertices[i];

    newArray[numberOfVertices] = newVertex;
    self.vertices = newArray;
}

but no luck. I'm not exactly confident in C so probably this is really trivial..

Upvotes: 1

Views: 1218

Answers (2)

Jakob
Jakob

Reputation: 982

here's how i do it now:

// re-allocate the array dynamically. 
// realloc() will act like malloc() if vertices == NULL
Vertex newVertex = {{x,y},{r,g,b,a}};
numberOfVertices++;
vertices = (Vertex *) realloc(vertices, sizeof(Vertex) * numberOfVertices);
if(vertices == NULL) NSLog(@"FAIL allocating memory for vertex array");
else vertices[numberOfVertices - 1] = newVertex;

// clean up memory once i don't need the array anymore
if(vertices != NULL) free(vertices);

i suppose icnivad's method above is more flexible since you can do more stuff with a NSMutableArray, but using plain C arrays with malloc/realloc should be (much?) faster .

Upvotes: 0

Todd Hopkinson
Todd Hopkinson

Reputation: 6903

This is how I just did it:

//verts is an NSMutableArray and I want to have an CGPoint c array to use with 
//  glVertexPointer(2, GL_FLOAT, 0, vertices);... so:

CGPoint vertices[[verts count]];
for(int i=0; i<[verts count]; i++)
{
    vertices[i] = [[verts objectAtIndex:i] CGPointValue];
}

Upvotes: 1

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