OpenGL & Xcode Colour Issue - c++

Moving from Visual Studio to Xcode to code in OpenGL and C++ I have come across an issue.
Trying to draw a simple cube in Xcode there is an issue (possibly with the depth buffer) that means the rendering of the cube is p
I have created a function that draws the cube panels using quads. My code runs and on Visual Studio displays the cube correctly. In Xcode, however, it seems to give priority to the latest drawn quad so that a panel of the cube appears to be in front of a panel it is behind. Attached is an example of the display I am getting in Xcode. Also, the code I have written.
The question I am asking is if anyone has had this issue before? Further, if anyone knows what is causing this issue and if there is a solution?
#include <stdlib.h>
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include <GLUT/GLUT.h>
#include <math.h>
char rendermode; // global variable for current rendering mode
/*
* Scene initialisation
*/
void InitGL(GLvoid)
{
glShadeModel(GL_SMOOTH); // Enable smooth shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black background
glClearDepth(1.0f); // Depth buffer setup
glEnable(GL_DEPTH_TEST); // Enables depth testing
glDepthFunc(GL_LEQUAL); // The type of depth testing to do
glEnable(GL_COLOR_MATERIAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}
void drawCube(float size){
glBegin(GL_QUADS);
//Front Panel (Black)
glColor3f(0.0, 0.0, 0.0);
glVertex3f(size, size, size);
glVertex3f(-size, size, size);
glVertex3f(-size, -size, size);
glVertex3f(size, -size, size);
//Back Panel (Blue)
glColor3f(0.0, 0.0, 1.0);
glVertex3f(size, size, -size);
glVertex3f(-size, size, -size);
glVertex3f(-size, -size, -size);
glVertex3f(size, -size, -size);
//Left Panel (Yellow)
glColor3f(1.0, 1.0, 0.0);
glVertex3f(-size, size, size);
glVertex3f(-size, -size, size);
glVertex3f(-size, -size, -size);
glVertex3f(-size, size, -size);
//Right Panel (Green)
glColor3f(0.0, 1.0, 0.0);
glVertex3f(size, size, size);
glVertex3f(size, -size, size);
glVertex3f(size, -size, -size);
glVertex3f(size, size, -size);
//Bottom Panel (Light Blue)
glColor3f(0.0, 1.0, 1.0);
glVertex3f(size, -size, size);
glVertex3f(-size, -size, size);
glVertex3f(-size, -size, -size);
glVertex3f(size, -size, -size);
//Top Panel (Pink)
glColor3f(1.0, 0.0, 1.0);
glVertex3f(size, size, size);
glVertex3f(-size, size, size);
glVertex3f(-size, size, -size);
glVertex3f(size, size, -size);
glEnd();
}
void idle (void)
{
glutPostRedisplay(); // trigger display callback
}
void display (void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
// set the camera
gluLookAt(5.0f, 5.0f, 10.0f,
0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f);
//TO DO: Draw a cube rather than a square
// different render mode
switch ( rendermode ) {
case 'f': // to display faces
drawCube(2);
break;
case 'v': // to display points
glBegin(GL_POINTS);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glEnd();
glPointSize(5);
break;
case 'e': // to display edges
glBegin(GL_LINES);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f( -1.0f, 1.0f,1.0f);
glVertex3f( -1.0f, -1.0f,1.0f);
glVertex3f( -1.0f, 1.0f,1.0f);
glVertex3f( 1.0f, 1.0f,1.0f);
glVertex3f( -1.0f, -1.0f,1.0f);
glVertex3f( 1.0f, -1.0f,1.0f);
glVertex3f( 1.0f, -1.0f,1.0f);
glVertex3f( 1.0f, 1.0f,1.0f);
glEnd();
break;
}
glutSwapBuffers();
}
/*
* The reshape function sets up the viewport and projection
*/
void reshape ( int width, int height )
{
// Prevent a divide by zero error by making height equal 1
if (height==0)
{
height=1;
}
glViewport(0,0,width,height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Need to calculate the aspect ratio of the window for gluPerspective
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
// Return to ModelView mode for future operations
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
/*
* Callback for standard keyboard presses
*/
void keyboard ( unsigned char key, int x, int y )
{
switch(key) {
// Exit the program when escape is pressed
case 27:
exit(0);
break;
// Switch render mode for v,e,f
case 'v':
rendermode='v';
break;
case 'e':
rendermode='e';
break;
case 'f':
rendermode='f';
break;
default:
break;
}
glutPostRedisplay();
}
// Arrow keys need to be handled in a separate function from other keyboard presses
void arrow_keys ( int a_keys, int x, int y )
{
switch ( a_keys ) {
case GLUT_KEY_UP:
glutFullScreen();
break;
case GLUT_KEY_DOWN:
glutReshapeWindow(500, 500);
break;
default:
break;
}
}
void mouseButton(int button, int state, int x, int y)
{
}
void mouseMove(int x, int y)
{
}
/*
* Entry point to the application
*/
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
glutInitWindowSize(500, 500);
glutCreateWindow("CW1 OpenGL Framework");
// glutFullScreen(); // Uncomment to start in full screen
InitGL();
rendermode='f';
// Callback functions
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutSpecialFunc(arrow_keys); // For special keys
glutMouseFunc(mouseButton);
glutMotionFunc(mouseMove);
glutIdleFunc(idle);
glutMainLoop();
}

glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
...
glEnable(GL_DEPTH_TEST);
You kinda need a depth buffer for GL_DEPTH_TEST to work. The OS isn't required to give you a depth buffer if you don't ask for one.
If you capital-N Need a depth buffer make sure explicitly request one:
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
^^^^^^^^^^

Related

Opengl/Glut keyboard input trouble

i have an assignment to draw a pyramid onto the screen and then rotate after i press the 'k' key in my keyboard.
Everything works ok, except the rotation part as the program doesn't seem to be noting me pressing the key. The code goes as follows:
void changeSize(int w, int h) {
if(h == 0)
h = 1;
float ratio = w * 1.0 / h;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, w, h);
// Set perspective
gluPerspective(45.0f ,ratio, 1.0f ,1000.0f);
// return to the model view matrix mode
glMatrixMode(GL_MODELVIEW);
}
void renderScene(void) {
// clear buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// set the camera
glLoadIdentity();
gluLookAt(5.0,5.0,5.0,
0.0,0.0,0.0,
0.0f,2.0f,0.0f);
// put the geometric transformations here
// put drawing instructions here
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
glBegin(GL_LINES);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-100.0f, 0.0f, 0.0f);
glVertex3f( 100.0f, 0.0f, 0.0f);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(0.0f, -100.0f, 0.0f);
glVertex3f(0.0f, 100.0f, 0.0f);
glColor3f(0.0f, 0.0f, 1.0f);
glVertex3f(0.0f, 0.0f, -100.0f);
glVertex3f(0.0f, 0.0f, 100.0f);
glEnd();
//triangulos da base
glBegin(GL_TRIANGLES);
glColor3f(255.0f,255.0f,255.0f);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glEnd();
//triangulos das faces
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(1.0f,0.0f,1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,-1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(-1.0f,0.0f,-1.0f);
glVertex3f(0.0f,2.0f,0.0f);
glVertex3f(-1.0f,0.0f,1.0f);
glEnd();
// End of frame
glutSwapBuffers();
}
// write function to process keyboard events
void rotate (unsigned char key, int x, int y) {
if (key == 'k')
glRotatef(45,1.0,1.0,0.0);
glutPostRedisplay();
}
int main(int argc, char **argv) {
// init GLUT and the window
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH|GLUT_DOUBLE|GLUT_RGBA);
glutInitWindowPosition(100,100);
glutInitWindowSize(1200,1200);
glutCreateWindow("CG#DI-UM");
// Required callback registry
glutDisplayFunc(renderScene);
glutReshapeFunc(changeSize);
// put here the registration of the keyboard callbacks
glutKeyboardFunc(rotate);
// OpenGL settings
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
// enter GLUT's main cycle
glutMainLoop();
return 0;
}
It seems that my program is not noting me pressing the key even tho i am. Im tried only printing the keys that are being pressed, and that works, so i'm really lost here.
glRotatef seem to have no effect in rotate, because glLoadIdentity() is called at the begin of renderScene. Actually glRotatef changes the current matrix, but when the scene is rendered (renderScene), then glLoadIdentity() loads the Identity matrix to the current matrix.
Anyway it is a bad style to do changes to the current matrix in input event callbacks. Change states and values of variables in the input events and use the variables to set the current model view matrix before the scene is rendered in renderScene.
Add a global variable angle:
float angle = 0.0f;
Change the value of the variable in renderScene. e.g:
void rotate (unsigned char key, int x, int y) {
if (key == 'k') {
angle += 45.0f;
glutPostRedisplay();
}
}
And apply the rotation to the current matrix in renderScene:
void renderScene(void) {
// clear buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// set the camera
glLoadIdentity();
gluLookAt(5.0,5.0,5.0,
0.0,0.0,0.0,
0.0f,2.0f,0.0f);
// apply rotation
glRotatef(angle, 1.0f, 1.0f, 0.0f);
// [...]
}

Zooming Issues with glutMouseWheelFunc

I tired implementing a simple zoom in/out using the glutMouseWheelFunc in VC++. I am able to achieve the zooming in/out but while doing so, the axes(GLlines) tend to disappear after zooming more than a certain level.
Am using the glutMouseWheelFunc to increase/decrease z- axis value in glTranslatef.
I have defined 'z' of glTranslatef for as camera distance:
float cDist= 30.0f; // camera distance
Then used it in glTranslatef as,
glTranslatef(0.0f, 0.0f, -cDist);
in display function below.
void display(void) {
glClearColor(0.0, 0.0, 0.0, 1.0); //clear the screen to black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);//clear the color buffer and the depth buffer
enable();
glLoadIdentity();
glTranslatef(0.0f, 0.0f, -cDist);
glRotatef(xrot, 1.0, 0.0, 0.0);
---------------
glBegin(GL_LINES);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f(-500, 0, 0);
glVertex3f(500, 0, 0);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(0, -500, 0);
glVertex3f(0, 500, 0);
glColor3f(0.0f, 0.0f, 1.0f);
glVertex3f(0, 0, -500);
glVertex3f(0, 0, 500);
glTranslated(-xpos, 0.0f, -zpos); //translate the screento the position of our camera
glColor3f(1.0f, 1.0f, 1.0f);
glutSwapBuffers();
}
Afterwards, I defined wheelfunc as,
void mouseWheel(int button, int dir, int x, int y)
{
if (dir > 0)
{
cDist = cDist++;
}
else
{
cDist= cDist--;
}
return;
}
and called it in main function with glutMouseWheelFunc(mouseWheel);
int main(int argc, char **argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_MULTISAMPLE);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow("Window");
glutDisplayFunc(display);
glutIdleFunc(display);
glutReshapeFunc(reshape);
glutMotionFunc(mouseMovement);
glutMouseWheelFunc(mouseWheel);---- here
-----
---
glutMainLoop();
return 0;
}
Is this approach of zooming in proper? if not, what could be the alternative ? Also how can I define axes(lines I drew) to full extent of the screen?
thanks for the help. Seems like I missed up setting up proper depth value for gluPerspective. Once I increased the depth value, zoom out/in was working fine

Entire object rotates

The idea from this code is to let a windmill like structure to rotate, the problem is that the entire object rotates instead of the windmill fan itself (not the red triangles only). here is the code (I use the keys to control speed)
#include <windows.h> // for MS Windows
#include <GL/glut.h> // GLUT, include glu.h and gl.h
float angle = 0.00002f;
int refreshMills = 30;
void initGL() {
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Black and opaque
}
void Timer(int value) {
glutPostRedisplay(); // Post re-paint request to activate display()
glutTimerFunc(refreshMills, Timer, 0); // next Timer call milliseconds later
}
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
glColor3f(1.0f, 0.0f, 0.0f)
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, 0.2f);
glVertex2f(-0.2f, 0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(0.4f, -0.2f);
glVertex2f(0.2f, -0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, -0.2f)
glVertex2f(-0.2f, -0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(0.4f, 0.2f);
glVertex2f(0.2f, 0.4f);
glEnd();
glRotatef(angle, 0.0f, 0.0f, 1.0f);
angle=angle+0.000002f;
glutPostRedisplay();
glBegin(GL_TRIANGLES);
glColor3f(1.0f, 1.0f, 1.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, -0.6f);
glVertex2f(0.4f, -0.6f);
glEnd();
glFlush();
glutSwapBuffers();
}
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 'a':{
angle+=1;
glutPostRedisplay();
}
case 's':
angle+=2;
glutPostRedisplay();
case 'd':
angle+=3
glutPostRedisplay();
case 'f':
angle=0;
}
}
}
int main(int argc, char** argv) {
glutInit(&argc, argv); // Initialize GLUTx
glutCreateWindow("Windmill"); // Create window with the given title
glutInitWindowSize(320, 320); // Set the window's initial width & height
glutInitWindowPosition(50, 50); // Position the window's initial top-left corner
glutDisplayFunc(display);
glutTimerFunc(0, Timer, 0);
glutSpecialFunc(specialKeys);
glutKeyboardFunc(keyboard);
initGL(); // Our own OpenGL initialization
glutMainLoop(); // Enter the event-processing loop
return 0;
}
You need to implement some sort of hierarchy(commonly a scene graph) here that uses transformation matrixes to do your transformations.
Basically, create a "Windmill" object that has its own transformation matrix. Then create a "Windmill Fan" object that has its own. Make the fan a child of the parent. The transformations essentially propagate down. Transform the Windmill, then transform the Windmill Fan.
Post on Scene Graphs
You may also want to check out the Game Development section of stackoverflow. These questions are usually not met with open arms here.
You need to clear your transformations before trying to draw a new frame. So, put a glLoadIdentity() after you glClear function.
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity(); // <-- put it here
glBegin(GL_TRIANGLES);
...
You need to call glRotate before drawing the rotating object. And before that, you need to push the current model view matrix onto the stack with glPushMatrix, then pop it with glPopMatrix before drawing the rest of the windmill.
Once you have a more complex scene you might consider using a scene graph. Note that the matrix functions like glRotate are now deprecated. You might consider switching to e.g. glm as soon as possible.
Try this:
#include <GL/glut.h> // GLUT, include glu.h and gl.h
void Timer(int value)
{
glutPostRedisplay(); // Post re-paint request to activate display()
glutTimerFunc(16, Timer, 0); // next Timer call milliseconds later
}
float rate = 1.0f;
void keyboard(unsigned char key, int x, int y)
{
switch (key)
{
case 'a':
rate=2;
break;
case 's':
rate=3;
break;
case 'd':
rate=4;
break;
case 'f':
rate=0;
break;
}
glutPostRedisplay();
}
float angle = 0.0f;
void display()
{
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Black and opaque
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
// base
glPushMatrix();
glBegin(GL_TRIANGLES);
glColor3f(1.0f, 1.0f, 1.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, -0.6f);
glVertex2f(0.4f, -0.6f);
glEnd();
glPopMatrix();
// prop
glPushMatrix();
glRotatef(angle, 0.0f, 0.0f, 1.0f);
angle=angle+rate;
glBegin(GL_TRIANGLES);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, 0.2f);
glVertex2f(-0.2f, 0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(0.4f, -0.2f);
glVertex2f(0.2f, -0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(-0.4f, -0.2f);
glVertex2f(-0.2f, -0.4f);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glVertex2f(0.4f, 0.2f);
glVertex2f(0.2f, 0.4f);
glEnd();
glPopMatrix();
glutSwapBuffers();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv); // Initialize GLUTx
glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
glutInitWindowSize(320, 320); // Set the window's initial width & height
glutInitWindowPosition(50, 50); // Position the window's initial top-left corner
glutCreateWindow("Windmill"); // Create window with the given title
glutDisplayFunc(display);
glutTimerFunc(0, Timer, 0);
glutKeyboardFunc(keyboard);
glutMainLoop(); // Enter the event-processing loop
return 0;
}

OpenGL Plane not showing up

I'm making a particle fountain in openGL, I have the particles functioning properly. I decided to add a plane to make it look like they are bouncing off from it. What I'm trying to get is something like this
Unfortunately what I'm getting is this
the plain doesn't seem to be appearing at all. I tried messing with the co-ordinates and that doesn't seem to do anything. This is the image I'm using as the texture, it's a 256 X 256 24bit bmp.
I load the texture in the init function, then call it before I render the particles in the following function
void Load_Plane(){
glEnable(GL_BLEND);
glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_SRC_ALPHA);
glColor4f(0.0f, 0.2f, 0.2f, 0.5f);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, txPlane);
glBegin(GL_QUADS);
glNormal3f(-10.0f, 0.0f, -10.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-10.0f, 0.0f, 10.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( 10.0f, 0.0f, 10.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( 10.0f, 0.0f, -10.0f);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-10.0f, 0.0f, -10.0f);
glEnd();
}
full code
// particle_fountain.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include<stdlib.h>
#include <stdio.h>
#include<Windows.h>
#include <time.h>
#include <GL\glut.h>
#include<GL\GLU.h>
#define MAX_PARTICLES 200 //max number of particles
#define MAX_BOUNCE_COUNT 5 //number of times a particle should bounce
#define MAX_PARTICLE_AGE 95
//Colours
float R = 0.8f;
float G = 0.2f;
float B = 0.0f;
float cR = 0.001f;
float cG = 0.002f;
float cB = 0.003f;
float Size = 0.02f; //size for points
GLuint txParticle;
GLuint txPlane;
struct PARTICLE {
float X,Y,Z; // Current position
float sX,sY,sZ; // Current Speed/Movement
float tX,tY,tZ; // Target Speed/Movement
float R,B,G; // Particle Colour
bool Active; // Is particle Active
int Age; // Age of the particle
int MaxAge; // Maximum Age before particle dies
int BounceCount;
} Particles[MAX_PARTICLES];
void Init_Particles();
void Activate_Particles();
void Adjust_Particles();
void Render_Particles();
bool LoadBitmapTexture(char * FileName, GLuint &texid);
void timer(int extra);
void Load_Plane();
void DrawGLscene();
void Reshape(GLsizei w, GLsizei h);
int main(int argc, char** argv){
glutInit(&argc,argv);
glutInitDisplayMode( GLUT_RGBA| GLUT_DOUBLE );
glutInitWindowSize( 640, 480 );
glutCreateWindow("Particle fountain");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-1.0, 1.0, -1.0, 1.0, 1.0, 10.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, -0.9, -3.0);
Init_Particles();
glutDisplayFunc(DrawGLscene);
glutTimerFunc(0, timer, 0);
glutMainLoop();
}
void timer(int extra)
{
glutPostRedisplay();
glutTimerFunc(20, timer, 0);
}
void Load_Plane(){
glEnable(GL_BLEND);
glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_SRC_ALPHA);
glColor4f(0.0f, 0.2f, 0.2f, 0.5f);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, txPlane);
glBegin(GL_QUADS);
glNormal3f(-10.0f, 0.0f, -10.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-10.0f, 0.0f, 10.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( 10.0f, 0.0f, 10.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( 10.0f, 0.0f, -10.0f);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-10.0f, 0.0f, -10.0f);
glEnd();
}
void DrawGLscene(){
Load_Plane();
glPushMatrix();
glScalef(1.0f, -1.0f, 1.0f);
Render_Particles();
glPopMatrix();
Render_Particles();
}
void Init_Particles(){
LoadBitmapTexture("./Particle.bmp", txParticle); //load the particle texture
LoadBitmapTexture("./Plain.bmp",txPlane); //load the plain texture
int p;
srand((int)time(NULL));
for(p=0; p<MAX_PARTICLES; p++){
Particles[p].Active = FALSE;
Particles[p].tX = 0.0f;
Particles[p].tY = -0.1f;
Particles[p].tZ = 0.0f;
}
}
void Activate_Particles(){
int p;
for(p=0; p<MAX_PARTICLES; p++){
if(!Particles[p].Active){
// Start the particle at 0,0,0 origin
Particles[p].X = 0.0f;
Particles[p].Y = 0.0f;
Particles[p].Z = 0.0f;
// The following lines set a random speed value
Particles[p].sX = (((float)((rand() % 100) + 1)) /
1000.0f) - 0.05f;
Particles[p].sY = (((float)((rand() % 100) + 50)) /
500.0f);
Particles[p].sZ = (((float)((rand() % 100) + 1)) /
1000.0f) - 0.05f;
// We also activate the particle
Particles[p].Active = true;
// Set it's Age to zero
Particles[p].Age = 0;
// We also assign a max age to the particles
Particles[p].MaxAge = MAX_PARTICLE_AGE;
// We Also reset the bouncecount to zero
Particles[p].BounceCount = 0;
//Adding the colours
Particles[p].R = R;
Particles[p].G = G;
Particles[p].B = B;
R+=cR;
G+=cG;
B+=cB;
if(R>1.0f){R=1.0f; cR=-cR;}
if(R<0.0f){R=0.0f; cR=-cR;}
if(G>1.0f){G=1.0f; cG=-cG;}
if(G<0.0f){G=0.0f; cG=-cG;}
if(B>1.0f){B=1.0f; cB=-cB;}
if(B<0.0f){B=0.0f; cB=-cB;}
return;
}
}
}
void Adjust_Particles(){
int p;
for(p=0; p<MAX_PARTICLES; p++){
// We move the speed towards the target speed by 1/20 (5%)
Particles[p].sX+= (Particles[p].tX - Particles[p].sX) / 20.0f;
Particles[p].sY+= (Particles[p].tY - Particles[p].sY) / 20.0f;
Particles[p].sZ+= (Particles[p].tZ - Particles[p].sZ) / 20.0f;
// Then we adjust the position of
// the particle by the new speed
Particles[p].X+= Particles[p].sX;
Particles[p].Y+= Particles[p].sY;
Particles[p].Z+= Particles[p].sZ;
// Now for the bounce code.
if(Particles[p].Y < 0.0f){
Particles[p].Y = 0.0f;
Particles[p].sY = -Particles[p].sY;
Particles[p].BounceCount++;
if(Particles[p].BounceCount > MAX_BOUNCE_COUNT){
Particles[p].Active = FALSE;
}
}
// And finally the age check
Particles[p].Age++;
if(Particles[p].Age > Particles[p].MaxAge){
Particles[p].Active = FALSE;
}
}
}
void Render_Particles(){
Activate_Particles();
Adjust_Particles();
glClear( GL_COLOR_BUFFER_BIT );
int p;
// Enable textures and bind our particle texture
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, txParticle);
// Disable Depth testing.
glDisable(GL_DEPTH_TEST);
// Enable blending
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR,GL_ONE);
for(p=0; p<MAX_PARTICLES; p++){
if(Particles[p].Active){
glColor4f(Particles[p].R,
Particles[p].G,
Particles[p].B, 1.0f);
glPushMatrix();
glTranslatef(Particles[p].X,
Particles[p].Y,
Particles[p].Z);
glBegin(GL_QUADS);
glNormal3f(0.0f, 0.0f, 1.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-Size, -Size, 0.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f(Size, -Size, 0.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f(Size, Size, 0.0f);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-Size, Size, 0.0f);
glEnd();
glPopMatrix();
}
}
glEnable(GL_DEPTH_TEST);
glutSwapBuffers();
}
bool LoadBitmapTexture(char * FileName, GLuint &texid){
HBITMAP hBMP; // Handle Of The Bitmap
BITMAP BMP; // Bitmap Structure
glGenTextures(1, &texid); // Create The Texture
hBMP=(HBITMAP)LoadImage(GetModuleHandle(NULL),
FileName,
IMAGE_BITMAP, 0, 0,
LR_CREATEDIBSECTION | LR_LOADFROMFILE
);
if (!hBMP) // Does The Bitmap Exist?
return FALSE; // If Not Return False
GetObject(hBMP, sizeof(BMP), &BMP); // Get The Object
// hBMP: Handle To Graphics Object
// sizeof(BMP): Size Of Buffer For Object Information
// &BMP: Buffer For Object Information
glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
// Pixel Storage Mode (Word Alignment / 4 Bytes)
// Typical Texture Generation Using Data From The Bitmap
glBindTexture(GL_TEXTURE_2D, texid);// Bind To The Texture ID
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_LINEAR); // Linear Min Filter
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
GL_LINEAR); // Linear Mag Filter
glTexImage2D(GL_TEXTURE_2D, 0, 3, BMP.bmWidth, BMP.bmHeight,
0, GL_BGR_EXT, GL_UNSIGNED_BYTE, BMP.bmBits);
DeleteObject(hBMP); // Delete The Object
return TRUE; // Loading Was Successful
}
It could be that you're not clearing the depth buffer.
It doesn't affect any of the particles because you are disabling depth test when you render them, but when you render the plane, depth test is enabled, and since the depth buffer has not been cleared it has a spaz and doesn't render the plane.
Do
glClear(GL_DEPTH_BUFFER_BIT);
before you render the plane to clear the depth buffer.
EDIT:
This must be it-
You are calling
glClear(GL_COLOR_BUFFER_BIT);
after you render the plane. Look at your DrawGLScene function:
Load_Plane(); // you are drawing the plane here
glPushMatrix();
glScalef(1.0f, -1.0f, 1.0f);
Render_Particles(); // this function calls "glClear( GL_COLOR_BUFFER_BIT );"
// so anything that you rendered before is now removed.
glPopMatrix();
Render_Particles(); // same goes for here.
The solution would be to remove the call to glClear from your Render_Particles function,
and add it to the top of DrawGLScene:
(New DrawGLScene Code)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
Load_Plane();
glPushMatrix();
glScalef(1.0f, -1.0f, 1.0f);
Render_Particles();
glPopMatrix();
Render_Particles();
EDIT #2:
You're calling glutSwapBuffers in the Render_Particles function.
Don't call it there. Call it at the end of DrawGLScene:

OpenGL texture inverted

I'm trying to map the input from my webcam to a plane in OpenGL. I'm using OpenCV to get the images from the webcam.
The problem I have is that the texture is vertically inverted, if my texture is "v", the current result is "^".
I want to fit the image taken from the webcam to my plane (2x2). Its lower left corner is -1, -1 and the upper right corner is 1,1.
The code is:
const int VIEWPORT_WIDTH = 640;
const int VIEWPORT_HEIGHT = 480;
const int KEY_ESCAPE = 27;
CvCapture* g_Capture;
IplImage* image;
GLint g_hWindow;
GLvoid InitGL();
GLvoid OnDisplay();
GLvoid OnReshape(GLint w, GLint h);
GLvoid OnKeyPress (unsigned char key, GLint x, GLint y);
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowPosition(100, 100);
glutInitWindowSize(VIEWPORT_WIDTH, VIEWPORT_HEIGHT);
g_hWindow = glutCreateWindow("Image");
image = cvLoadImage("average.jpg", 1);
gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB, image->width, image->height, GL_RGB, GL_UNSIGNED_BYTE, image->imageData);
InitGL();
glutMainLoop();
return 0;
}
GLvoid InitGL()
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glutDisplayFunc(OnDisplay);
glutReshapeFunc(OnReshape);
glutKeyboardFunc(OnKeyPress);
}
GLvoid OnDisplay(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
glPushMatrix();
glTranslatef(0.0f, 0.0f, -2.5f);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glEnd();
glPopMatrix();
glutSwapBuffers();
}
GLvoid OnReshape(GLint width, GLint height)
{
if (height==0)
height=1;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, width, height);
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height, 1.0f, 10.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt( 0.0, 0.0, 0.0, 0.0, 0.0, -6.0, 0.0f, 1.0f, 0.0f);
}
GLvoid OnKeyPress(unsigned char key, int x, int y)
{
switch (key) {
case KEY_ESCAPE:
cvReleaseImage(&image);
glutDestroyWindow(g_hWindow);
exit(0);
break;
}
glutPostRedisplay();
}
BTW. In this code I'm loading an image instead of getting from the webcam.
Any suggestion?
Flip the texture coordinates on the quad you're rendering. OpenGL does store texture "upside-down" from how most people assume they'd be, so the simplest way to handle it is just work with OGL.
glTexCoord2f(0.0f, 1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glTexCoord2f(1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glTexCoord2f(1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glTexCoord2f(0.0f, 0.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
should do it, I think.