OSX Mountain Lion OpenGL - glDrawPixels() not working - macos

Question

I am trying to get some basic demos to work on OSX Mountain Lion for OpenGL. Some work, but the basic ones aren't working. Specifically, I am getting garbage out on my X window. Here's the code from a demo (sorry if formatting is messed up):
/* W B Langdon at MUN 10 May 2007
* Program to demonstarte use of OpenGL's glDrawPixels
*/
#ifdef _WIN32
#include <windows.h>
#endif
#include <GL/gl.h>
#include <GL/glext.h>
#include <GL/glut.h>
#include <iostream>
#include <sstream>
#include "math.h"
unsigned int window_width = 512, window_height = 512;
const int size=window_width*window_height;
struct rgbf {float r; float g; float b;};
//WBL 9 May 2007 Based on
//http://www.codeguru.com/cpp/w-d/dislog/commondialogs/article.php/c1861/
//Common.h
void toRGBf(const float h, const float s, const float v,
rgbf* rgb)
{
/*
RGBType rgb;
if(!h && !s)
{
rgb.r = rgb.g = rgb.b = v;
}
*/
//rgbf* rgb = (rgbf*) out;
double min,max,delta,hue;
max = v;
delta = max * s;
min = max - delta;
hue = h;
if(h > 300 || h <= 60)
{
rgb->r = max;
if(h > 300)
{
rgb->g = min;
hue = (hue - 360.0)/60.0;
rgb->b = ((hue * delta - min) * -1);
}
else
{
rgb->b = min;
hue = hue / 60.0;
rgb->g = (hue * delta + min);
}
}
else
if(h > 60 && h < 180)
{
rgb->g = max;
if(h < 120)
{
rgb->b = min;
hue = (hue/60.0 - 2.0 ) * delta;
rgb->r = min - hue;
}
else
{
rgb->r = min;
hue = (hue/60 - 2.0) * delta;
rgb->b = (min + hue);
}
}
else
{
rgb->b = max;
if(h < 240)
{
rgb->r = min;
hue = (hue/60.0 - 4.0 ) * delta;
rgb->g = (min - hue);
}
else
{
rgb->g = min;
hue = (hue/60 - 4.0) * delta;
rgb->r = (min + hue);
}
}
}
//Convert a wide range of data values into nice colours
void colour(const float data, float* out) {
//convert data to angle
const float a = atan2(data,1)/(2*atan2(1,1)); // -1 .. +1
const float angle = (1+a)*180; //red=0 at -1,+1
const float saturation = 1;
const float h = (data<-1||data>1)? 1 : fabs(data);
toRGBf(angle,saturation,h,(rgbf*)out);
}
void display()
{
//Create some nice colours (3 floats per pixel) from data -10..+10
float* pixels = new float[size*3];
for(int i=0;i<size;i++) {
colour(10.0-((i*20.0)/size),&pixels[i*3]);
}
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//http://msdn2.microsoft.com/en-us/library/ms537062.aspx
//glDrawPixels writes a block of pixels to the framebuffer.
glDrawPixels(window_width,window_height,GL_RGB,GL_FLOAT,pixels);
glFlush();
glutSwapBuffers();
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowSize(window_width, window_height);
glutCreateWindow("OpenGL glDrawPixels demo");
glutDisplayFunc(display);
//glutReshapeFunc(reshape);
//glutMouseFunc(mouse_button);
//glutMotionFunc(mouse_motion);
//glutKeyboardFunc(keyboard);
//glutIdleFunc(idle);
glEnable(GL_DEPTH_TEST);
glClearColor(0.0, 0.0, 0.0, 1.0);
//glPointSize(2);
glutMainLoop();
}
This is what I get:
wrong

Answer 1

Please consider glDrawPixels as not relevant anymore. It has been deprecated (read: do not use in new code) from OpenGL ever since version OpenGL-2. It has been depreciated (different word, note the 'i' – read: Has been removed) ever since OpenGL-3 core profile.
Use textured quads instead.