glDrawArrays(GL_POINTS, 0, vertexCount); draws only one point - objective-c

Question

I use a NSOpenGLView.
- (void)initGL
{
// Setup OpenGL states
[[self openGLContext] makeCurrentContext];
// Setup OpenGL states
glMatrixMode(GL_PROJECTION);
CGRect frame = self.bounds;
// Setup the view port in Pixels
glOrtho(0, frame.size.width, 0, frame.size.height, -1, 1);
glViewport(0, 0, frame.size.width, frame.size.height);
glMatrixMode(GL_MODELVIEW);
glDisable(GL_DITHER);
glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_VERTEX_ARRAY);
glEnable(GL_BLEND);
//glEnable(GL_LINE_SMOOTH);
glEnable(GL_POINT_SMOOTH);
glEnable(GL_POINT_SPRITE);
glTexEnvf(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);
self.pointSize = pointSizeForDrawing;
}
Framebuffer creation and binding.
- (BOOL)createFramebuffer
{
//Generating two buffers
glGenRenderbuffers( NumRenderbuffers, renderbuffer );
glBindRenderbuffer( GL_RENDERBUFFER, renderbuffer[Color]);
glRenderbufferStorage( GL_RENDERBUFFER, GL_RGBA, self.bounds.size.width, self.bounds.size.height);
glBindRenderbuffer( GL_RENDERBUFFER, renderbuffer[Depth] );
glRenderbufferStorage( GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, self.bounds.size.width, self.bounds.size.height);
//Generating framebuffer
glGenFramebuffers( 1, &framebuffer );
glBindFramebuffer( GL_DRAW_FRAMEBUFFER, framebuffer );
glFramebufferRenderbuffer( GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer[Color] );
glFramebufferRenderbuffer( GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderbuffer[Depth] );
glEnable( GL_DEPTH_TEST );
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
DLog(#"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
return NO;
}
return YES;
}
Line rendering
- (void)renderLineFromPoint:(CGPoint)start ToPoint:(CGPoint)end
{
GLsizei vertexCount = 0;
DLog(#"start: %# end %#", NSStringFromCGPoint(start), NSStringFromCGPoint(end));
// Add points to the buffer so there are drawing points every X pixels
int count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y - start.y) * (end.y - start.y)) / brushPixelStep), 1);
for(int i = 0; i < count; ++i)
{
if(vertexCount == vertexMax)
{
vertexMax = 2 * vertexMax;
vertexBuffer = realloc(vertexBuffer, vertexMax * 2 * sizeof(GLfloat));
}
vertexBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i / (GLfloat)count);
vertexBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i / (GLfloat)count);
vertexCount += 1;
}
// Render the vertex array
glBindFramebuffer( GL_DRAW_FRAMEBUFFER, framebuffer);
glClear(GL_DEPTH_BUFFER_BIT);
glVertexPointer(2, GL_FLOAT, 0, vertexBuffer);
glDrawArrays(GL_POINTS, 0, vertexCount);
}
And finally display buffer
- (void)displayBuffer
{
DLog(#"Display");
glBindFramebuffer( GL_READ_FRAMEBUFFER, framebuffer );
glBindFramebuffer( GL_DRAW_FRAMEBUFFER, 0 );
glViewport(0, 0, self.bounds.size.width, self.bounds.size.height);
glBlitFramebuffer( 0, 0, self.bounds.size.width, self.bounds.size.height, 0, 0, self.bounds.size.width, self.bounds.size.height, GL_COLOR_BUFFER_BIT, GL_NEAREST );
glSwapAPPLE();
}
It does not matter if I change line glDrawArrays(GL_POINTS, 0, vertexCount); to glDrawArrays(GL_POINTS, 0, 1);. The effect is still the same despite value of vertexCount different than 1. Any ideas?

Answer 1

First possible problem:
glVertexPointer(2, GL_FLOAT, 0, vertexBuffer);
As I understand vertexBuffer is an array of structures. So the error could be that the third parameter is 0 but it should be the size of this structure. For example:
CVertex3 v[3];
...
glVertexPointer(3,GL_FLOAT,sizeof(CVertex3),v);
Updated
Second possible problem:
try to remove glEnable(GL_DEPTH_TEST); it wouldn't work properly but I think I have seen the similar situation in Internet