Setting up vertices using pointer not working - ios

Question

im currently working on some OpenGL Basics with OpenGL ES 2.0.
If i setup the vertices as constants in the top the triangle gets drawn; if i try to set them up in a method using a pointer, nothing is drawn.
What am I missing?
#import "CometGLViewController.h"
typedef struct {
float Position[3];
float Color[4];
} Vertex;
//vertices store information for each "point" used to draw a triangle
Vertex* Vertices; // NOT DRAWING
//const Vertex Vertices[] = {
// {{0, 0, 0},{0, 0, 0, 1}},
// {{1, 1, 0}, {1, 0, 0, 1}},
// {{0, 1, 0}, {1, 0, 0, 1}},
//}; // THIS WORKS
//Used to reuse vertices
const GLubyte Indices[] = {
0, 1, 2,
};
... some other stuff
- (void)viewDidLoad
{
[super viewDidLoad];
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
if (!self.context) {
NSLog(#"Failed to create ES context");
}
GLKView *view = (GLKView *)self.view;
view.context = self.context;
view.drawableMultisample = GLKViewDrawableMultisample4X;
[self setupVertices];
[self setupGL];
}
...
#pragma mark - GLKViewDelegate
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
glClearColor(_curRed, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
[self.effect prepareToDraw];
glBindVertexArrayOES(_vertexArray);
glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);
}
...
#pragma mark - OpenGL stuff
- (void)setupGL {
[EAGLContext setCurrentContext:self.context];
glEnable(GL_CULL_FACE);
glGenVertexArraysOES(1, &_vertexArray);
glBindVertexArrayOES(_vertexArray);
// ----- create new buffer, work with "vertexBuffer", glBufferData sends data for opengl usage
glGenBuffers(1, &_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
glGenBuffers(1, &_indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);
// ----- Setup vertices attributes
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
glEnableVertexAttribArray(GLKVertexAttribColor);
glVertexAttribPointer(GLKVertexAttribColor, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Color));
}
- (void)tearDownGL {
[EAGLContext setCurrentContext:self.context];
glDeleteBuffers(1, &_vertexBuffer);
glDeleteBuffers(1, &_indexBuffer);
glDeleteVertexArraysOES(1, &_vertexArray);
self.effect = nil;
}
- (void)setupVertices
{ // test
int points = 3;
Vertices = malloc(sizeof(Vertex) * points);
Vertex v = {{0, 0, 0}, {0, 0, 0, 1}};
Vertices[0] = v;
Vertex v1 = {{1, 1, 0}, {0, 1, 0, 1}};
Vertices[1] = v1;
Vertex v2 = {{0, 1, 1}, {1, 0, 0, 1}};
Vertices[2] = v2;
}
#end

Answer 1

Change
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
to
glBufferData(GL_ARRAY_BUFFER, sizeof(vertex) * 3, Vertices, GL_STATIC_DRAW);
Your problem is that sizeof(vertices) works differently for pointers than for arrays allocated on the stack.