I'm trying to code a camera with glTranslate/glRotate. To implement the look-up / look-down functions I need all the objects in my rendering space to rotate around a point (that is, where the "camera" is at), point which usually differs from the origin. Still, things keep rotating around the origin. Is there a way to specify a different point?
EDIT: Added code
Thanks for your fast reply. It seems that I can't get it working right no matter what, so I've decided to add my code; I'd much appreciate if someone could take a look at it and tell me what changes are needed in order to translate/rotate/translate back.
#include <iostream>
#include <cmath>
#include <GLUT/GLUT.h>
const double roaming_step = .13;
double z_offset = .0;
double y_offset = .0;
double x_offset = .0;
const double angle_step = 1.5;
double angle_xz = .0;
double angle_yz = .0;
bool keyStates[256] = { false };
void drawFloor()
{
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_QUADS);
glVertex3f(-3.0, -1.0, 3.0);
glVertex3f(-3.0, -1.0, -3.0);
glVertex3f(3.0, -1.0, -3.0);
glVertex3f(3.0, -1.0, 3.0);
glEnd();
}
void drawBalls()
{
glTranslatef(-3.0, -.5, -3.0);
glColor3f(.8, .1, .1);
for(int i = 0; i < 3; i++)
{
glPushMatrix();
glTranslatef(.0, -.5, i * 3);
for(int j = 0; j < 3; j++)
{
glPushMatrix();
glTranslatef(j * 3, .0, .0);
glutSolidSphere(.5, 20, 20);
glPopMatrix();
}
glPopMatrix();
}
}
void keyPressed(unsigned char key, int x, int y)
{
keyStates[key] = true;
}
void keyReleased(unsigned char key, int x, int y)
{
keyStates[key] = false;
}
void keyboardOperations()
{
if(keyStates['w'])
z_offset += roaming_step;
if(keyStates['s'])
z_offset -= roaming_step;
if(keyStates['a'])
x_offset += roaming_step;
if(keyStates['d'])
x_offset -= roaming_step;
if(keyStates['i'])
{
angle_xz -= angle_step;
if(angle_xz < .0)
angle_xz += 360.0;
}
if(keyStates['o'])
{
angle_xz += angle_step;
if(angle_xz >= 360.0)
angle_xz -= 360.0;
}
if(keyStates['u'])
{
angle_yz -= angle_step;
if(angle_yz < .0)
angle_yz += 360.0;
}
if(keyStates['j'])
{
angle_yz += angle_step;
if(angle_yz >= 360.0)
angle_yz -= 360.0;
}
if(keyStates['q'])
exit(0);
}
// I guess it has to be done in this function
// but didn't get how
void camera()
{
glLoadIdentity();
// Forward / Backward
glTranslated(.0, .0, z_offset);
// Left / Right
glTranslated(x_offset, .0, .0);
// XZ Rotation
glRotated(angle_xz, .0, 1.0, .0);
// YZ Rotation
glRotated(angle_yz, 1.0, .0, .0);
}
void display(void)
{
keyboardOperations();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
camera();
drawFloor();
drawBalls();
glutSwapBuffers();
}
void reshape(int width, int height)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, width, height);
GLdouble aspect = (GLdouble) width / (GLdouble) height;
gluPerspective(60, aspect, 1, 100);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutInitWindowPosition(0, 0);
glutCreateWindow("openGLtest3");
glClearColor(.0, .0, .0, .0);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_FLAT);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutIdleFunc(display);
glutIgnoreKeyRepeat(true);
glutKeyboardFunc(keyPressed);
glutKeyboardUpFunc(keyReleased);
glutMainLoop();
return 0;
}
In openGL, glRotation fuction takes origin as a reference. In order to rotate around a point (your camera coordinate in this case) you should translate your camera position to the origin (Translate all your objects accordingly) and then apply rotation function.And then you can translate your camera back (with all your objects)
lets say your camera position is (a,b,c) so your code should be something like :
foreach object
{
glPushMatrix();
glTranslate(a,b,c);
glRotate(...);
glTranslate(-a,-b,-c);
//render
glPopMatrix();
}
Related
#include <stdio.h> // this library is for standard input and output
#include "glut.h"// this library is for glut the OpenGL Utility Toolkit
#include <math.h>
float squareX = 0.0f;
float squareY = -0.3f;
float squareZ = 0.0f;
static int flag = 1;
void drawShape(void) {
glTranslatef(squareX, squareY, squareZ);
glBegin(GL_POLYGON);
glColor3f(1.0, 0.0, 0.0);
glVertex2f(162, 50);
glVertex2f(162, 10);
glVertex2f(220, 10);
glVertex2f(220, 50);
glVertex2f(162, 50);
glEnd();
}
void initRendering() {
glEnable(GL_DEPTH_TEST);
}
// called when the window is resized
void handleResize(int w, int h) {
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0f, (float)w, 0.0f, (float)h, -1.0f, 1.0f);
}
void drawScene() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
drawShape();
glutSwapBuffers();
}
// make the square go up
void update(int value) {
if (flag) {
squareY += 1.0f;
if (squareY > 400.0) {
flag = 0;
}
}
glutPostRedisplay();
glutTimerFunc(25, update, 0);
}
// make the square go right
/* void update(int value) {
if (flag) {
squareX += 1.0f;
if (squareX > 400.0) {
flag = 0;
}
}
glutPostRedisplay();
glutTimerFunc(25, update, 0);
} */
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(400, 400);
glutCreateWindow("Moving Square");
initRendering();
glutDisplayFunc(drawScene);
glutReshapeFunc(handleResize);
glutTimerFunc(25, update, 0);
glutMainLoop();
return(0);
}
I have uploaded this code before but this time I made the square go all the way up. The code just moves the square up, but I don't know how to position it on the left once it reaches the top, so then I can make it move to the right. I have uploaded a demonstration on how I want it to look below.
Preview:
What I want it to do next:
I recommend to initialize the variables squareX, squareY and squareZ with the start position of the rectangle:
float squareX = 162.0f;
float squareY = 0.0f;
float squareZ = 0.0f;
Do not draw a rectangle specific position, but draw a rectangle on the position (0,0) with a length (width, height). Let the model matrix (set by glTranslatef), do the job of the positioning:
void drawShape(void)
{
float width = 58.0f;
float height = 40.0f;
glTranslatef(squareX, squareY, squareZ);
glBegin(GL_POLYGON);
glColor3f(1.0, 0.0, 0.0);
glVertex2f(0, 0);
glVertex2f(width, 0);
glVertex2f(width, height);
glVertex2f(0, height);
glVertex2f(0, 0);
glEnd();
}
Use a variable state, which has stated the direction of the current movement:
int state = 1; // 0: stop; 1: move up; 2: move right
If the rectangle a certain position has reached, then the state has to be changed and a the new start position can be set. At the final position, the rectangle can stop or the process can even be restarted:
void update(int value)
{
if (state == 1) // 1 : move up
{
squareY += 1.0f;
if (squareY > 400.0)
{
state = 2;
squareX = 0.0f;
squareY = 180.0f;
}
}
else if (state == 2) // 2 : move right
{
squareX += 1.0f;
if (squareX > 400.0)
{
state = 0;
// restart
//state = 1;
//squareX = 162.0f;
//squareY = 0.0f;
}
}
glutPostRedisplay();
glutTimerFunc(25, update, 0);
}
I am trying to generate the Sierpinski Gasket using a function that draws dot patterns and will generate the gasket.
But when I compile and run the program it displays nothing but black screen. What's causing the problem?
Here is my code:
#include <Windows.h>
#include <gl/GL.h>
#include <glut.h>
void myInit(void) {
glClearColor(1.0, 1.0, 1.0, 0.0);
glColor3f(0.0f, 0.0f, 0.0f);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, 640.0, 0.0, 480.0);
}
class GLintPoint {
public:
GLint x, y;
};
int random(int m) {
return rand() % m;
}
void drawDot(GLint x, GLint y)
{
glBegin(GL_POINTS);
glVertex2i(x, y);
glEnd();
}
void Sierpinski(void) {
GLintPoint T[3] = {{ 10, 10 }, {300, 30}, {200, 300}};
int index = random(3);
GLintPoint point = T[index];
for (int i = 0; i < 1000; i++)
{
index = random(3);
point.x = (point.x + T[index].x) / 2;
point.y = (point.y + T[index].y) / 2;
drawDot(point.x, point.y);
}
glFlush();
}
void main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(640, 480);
glutInitWindowPosition(100, 150);
glutCreateWindow("Sierpinski Gasket");
glutDisplayFunc(drawDot);
myInit();
glutMainLoop();
}
If you want to draw black dots on a white background, then you have to clear glClear the background:
glClear( GL_COLOR_BUFFER_BIT );
Note, glClearColor sets the color which is used to clear the view port, but doesn't clear anything itself.
Your code should look somehow like this:
void drawDot(GLint x, GLint y)
{
glVertex2i(x, y);
}
void Sierpinski(void) {
GLintPoint T[3] = {{ 10, 10 }, {300, 30}, {200, 300}};
int index = random(3);
GLintPoint point = T[index];
glClearColor(1.0, 1.0, 1.0, 1.0); // set up white clear color
glClear( GL_COLOR_BUFFER_BIT ); // clear the back ground (white)
glMatrixMode( GL_MODELVIEW );
glPushMatrix(); // setup model matrix
glScalef( 1.5f, 1.5f, 1.0f ); // scale the point distribution
glColor3f( 0.0f, 0.0f, 0.0f ); // set black draw color
glPointSize( 5.0f ); // set the size of the points
glBegin(GL_POINTS);
for (int i = 0; i < 1000; i++)
{
index = random(3);
point.x = (point.x + T[index].x) / 2;
point.y = (point.y + T[index].y) / 2;
drawDot(point.x, point.y);
}
glEnd();
glPopMatrix(); // reset model matrix
glFlush();
}
I'm trying to draw simple circle with C++/OpenGl
my code is:
#include <GL/glut.h>
#include <math.h>
void Draw() {
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_QUADS);
glColor3f (0.0, 0.0, 0.0);
glVertex3f (0.1, 0.1, 0.0);
glVertex3f (0.9, 0.1, 0.0);
glVertex3f (0.9, 0.9, 0.0);
glVertex3f (0.1, 0.9, 0.0);
glEnd();
glFlush();
}
void DrawCircle(float cx, float cy, float r, int num_segments)
{
glBegin(GL_LINE_LOOP);
for(int ii = 0; ii < num_segments; ii++)
{
float theta = 2.0f * 3.1415926f * float(ii) / float(num_segments);//get the current angle
float x = r * cosf(theta);//calculate the x component
float y = r * sinf(theta);//calculate the y component
glVertex2f(x + cx, y + cy);//output vertex
}
glEnd();
}
void Initialize() {
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
int main(int iArgc, char** cppArgv) {
glutInit(&iArgc, cppArgv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(950, 500);
glutInitWindowPosition(200, 200);
glutCreateWindow("Universum");
Initialize();
glutDisplayFunc(Draw);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 1.0, 1.0);
DrawCircle(0.5, 0.5, 0.2, 5);
glutMainLoop();
return 0;
}
I'm beginner with OpenGL and now i'm starting to learn,
Can someone please explain me why i don't get the circle (i only see the black box),
Thanks!
It looks like immediately after you draw the circle, you go into the main glut loop, where you've set the Draw() function to draw every time through the loop. So it's probably drawing the circle, then erasing it immediately and drawing the square. You should probably either make DrawCircle() your glutDisplayFunc(), or call DrawCircle() from Draw().
#include <Windows.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define window_width 1080
#define window_height 720
void drawFilledSun(){
//static float angle;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0, 0, -10);
int i, x, y;
double radius = 0.30;
//glColor3ub(253, 184, 19);
glColor3ub(255, 0, 0);
double twicePi = 2.0 * 3.142;
x = 0, y = 0;
glBegin(GL_TRIANGLE_FAN); //BEGIN CIRCLE
glVertex2f(x, y); // center of circle
for (i = 0; i <= 20; i++) {
glVertex2f (
(x + (radius * cos(i * twicePi / 20))), (y + (radius * sin(i * twicePi / 20)))
);
}
glEnd(); //END
}
void DrawCircle(float cx, float cy, float r, int num_segments) {
glBegin(GL_LINE_LOOP);
for (int ii = 0; ii < num_segments; ii++) {
float theta = 2.0f * 3.1415926f * float(ii) / float(num_segments);//get the current angle
float x = r * cosf(theta);//calculate the x component
float y = r * sinf(theta);//calculate the y component
glVertex2f(x + cx, y + cy);//output vertex
}
glEnd();
}
void main_loop_function() {
int c;
drawFilledSun();
DrawCircle(0, 0, 0.7, 100);
glutSwapBuffers();
c = getchar();
}
void GL_Setup(int width, int height) {
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glEnable(GL_DEPTH_TEST);
gluPerspective(45, (float)width / height, .1, 100);
glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitWindowSize(window_width, window_height);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutCreateWindow("GLUT Example!!!");
glutIdleFunc(main_loop_function);
GL_Setup(window_width, window_height);
glutMainLoop();
}
This is what I did. I hope this helps. Two types of circle are here. Filled and unfilled.
There is another way to draw a circle - draw it in fragment shader.
Create a quad:
float right = 0.5;
float bottom = -0.5;
float left = -0.5;
float top = 0.5;
float quad[20] = {
//x, y, z, lx, ly
right, bottom, 0, 1.0, -1.0,
right, top, 0, 1.0, 1.0,
left, top, 0, -1.0, 1.0,
left, bottom, 0, -1.0, -1.0,
};
Bind VBO:
unsigned int glBuffer;
glGenBuffers(1, &glBuffer);
glBindBuffer(GL_ARRAY_BUFFER, glBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(float)*20, quad, GL_STATIC_DRAW);
and draw:
#define BUFFER_OFFSET(i) ((char *)NULL + (i))
glEnableVertexAttribArray(ATTRIB_VERTEX);
glEnableVertexAttribArray(ATTRIB_VALUE);
glVertexAttribPointer(ATTRIB_VERTEX , 3, GL_FLOAT, GL_FALSE, 20, 0);
glVertexAttribPointer(ATTRIB_VALUE , 2, GL_FLOAT, GL_FALSE, 20, BUFFER_OFFSET(12));
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
Vertex shader
attribute vec2 value;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
varying vec2 val;
void main() {
val = value;
gl_Position = projectionMatrix*viewMatrix*vertex;
}
Fragment shader
varying vec2 val;
void main() {
float R = 1.0;
float R2 = 0.5;
float dist = sqrt(dot(val,val));
if (dist >= R || dist <= R2) {
discard;
}
float sm = smoothstep(R,R-0.01,dist);
float sm2 = smoothstep(R2,R2+0.01,dist);
float alpha = sm*sm2;
gl_FragColor = vec4(0.0, 0.0, 1.0, alpha);
}
Don't forget to enable alpha blending:
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
UPDATE: Read more
We will find the value of X and Y from this image. We know, sinθ=vertical/hypotenuse and cosθ=base/hypotenuse from the image we can say X=base and Y=vertical. Now we can write X=hypotenuse * cosθ and Y=hypotenuse * sinθ.
Now look at this code
void display(){
float x,y;
glColor3f(1, 1, 0);
for(double i =0; i <= 360;){
glBegin(GL_TRIANGLES);
x=5*cos(i);
y=5*sin(i);
glVertex2d(x, y);
i=i+.5;
x=5*cos(i);
y=5*sin(i);
glVertex2d(x, y);
glVertex2d(0, 0);
glEnd();
i=i+.5;
}
glEnd();
glutSwapBuffers();
}
glBegin(GL_POLYGON); // Middle circle
double radius = 0.2;
double ori_x = 0.0; // the origin or center of circle
double ori_y = 0.0;
for (int i = 0; i <= 300; i++) {
double angle = 2 * PI * i / 300;
double x = cos(angle) * radius;
double y = sin(angle) * radius;
glVertex2d(ori_x + x, ori_y + y);
}
glEnd();
Here is a code to draw a fill elipse, you can use the same method but replacing de xcenter and y center with radius
void drawFilledelipse(GLfloat x, GLfloat y, GLfloat xcenter,GLfloat ycenter) {
int i;
int triangleAmount = 20; //# of triangles used to draw circle
//GLfloat radius = 0.8f; //radius
GLfloat twicePi = 2.0f * PI;
glBegin(GL_TRIANGLE_FAN);
glVertex2f(x, y); // center of circle
for (i = 0; i <= triangleAmount; i++) {
glVertex2f(
x + ((xcenter+1)* cos(i * twicePi / triangleAmount)),
y + ((ycenter-1)* sin(i * twicePi / triangleAmount))
);
}
glEnd();
}
I have done it using the following code,
glBegin(GL.GL_LINE_LOOP);
for(int i =0; i <= 300; i++){
double angle = 2 * Math.PI * i / 300;
double x = Math.cos(angle);
double y = Math.sin(angle);
gl.glVertex2d(x,y);
}
glEnd();
glBegin(GL_POLYGON);
double x = 2;
double y = 2;
for (int i = 0; i <= 360; i++) {
glVertex2d(x * sin(i), y * cos(i));
}
glEnd();
I have to make a bowling game in openGL. This is the code I have so far. What it does that it draws a ball and is moved accordingly when an arrow key is pressed.
So far, I have that ball moving, that is fine. What I want to do that other point I have created, that should not be moved. Because, when that ball reaches to that point, it should be drop or something I will make that obstacle is dropped.
The code is written in Eclipse IDE.
#include <stdio.h>
#include <GL/glut.h>
#include <math.h>
#include <stdio.h> /* printf, scanf, puts, NULL */
float posX = 0, posY = -0.1, posZ = 0;
GLfloat rotation = 90.0;
double x, y, angle;
#define PI 3.1415926535898
GLint circle_points = 50;
void reshape(int width, int heigth) {
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//clip the windows so its shortest side is 2.0
if (width < heigth) {
glOrtho(-2.0, 2.0, -2.0 * (GLfloat) heigth / (GLfloat) width,
2.0 * (GLfloat) heigth / (GLfloat) width, 2.0, 2.0);
} else {
glOrtho(-2.0, 2.0, -2.0 * (GLfloat) width / (GLfloat) heigth,
2.0 * (GLfloat) width / (GLfloat) heigth, 2.0, 2.0);
}
// set viewport to use the entire new window
glViewport(0, 0, width, heigth);
}
void circ() {
glColor3f(0.0, 0.0, 1.0);
glPointSize(11.0);
glBegin(GL_POINTS);
glVertex3f(0.1, 0.1, 0.0);
glEnd();
glBegin(GL_TRIANGLE_FAN);
for (int i = 0; i <= 300; i++) {
angle = 2 * PI * i / 300;
x = cos(angle) / 20;
y = sin(angle) / 20;
glVertex2d(x, y);
}
glEnd();
}
void display() {
//Clear Window
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glTranslatef(posX, posY, posZ);
circ();
glPopMatrix();
glFlush();
}
void init() {
// set clear color to black
glClearColor(1.0, 1.0, 1.0, 0.0);
// set fill color to white
glColor3f(1.0, 1.0, 1.0);
//This is the default view and these statements could be removed
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-1.0, 1.0, -1.0, 1.0);
}
float move_unit = 0.02f;
void keyboardown(int key, int x, int y) {
switch (key) {
case GLUT_KEY_RIGHT:
posX += move_unit;
break;
case GLUT_KEY_LEFT:
posX -= move_unit;
break;
case GLUT_KEY_UP:
posY += move_unit;
break;
case GLUT_KEY_DOWN:
posY -= move_unit;
break;
default:
break;
}
glutPostRedisplay();
}
int main(int argc, char** argv) {
//initialize mode and open a windows in upper left corner of screen
//Windows tittle is name of program
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(600, 500);
glutInitWindowPosition(0, 0);
glutCreateWindow("Practice 1");
glutDisplayFunc(display);
init();
glutSpecialFunc(keyboardown);
glutMainLoop();
}
Modern graphics APIs simulating finite state machine. That means that before Draw calls you must fully configure (or leave default) graphics pipeline "machine":
SetStates(); // Configure pipeline state: set geometry, textures, matrices, etc.
Begin();
Draw(); // Render frame according to current pipeline configuration (state)
End(); // Swap screen buffers
In case of many objects, you can just wrap all stuff with for loop:
for( each_object )
{
SetStates(); // current object's vertex/index buffer, texture, matrices, etc.
Begin();
Draw();
End();
}
Not very efficient. Next step of improvement might include: frustum culling, instancing, vertex buffers merging, texture atlases, draw calls sorting, etc.
BTW, consider using Vertex Buffer Objects (VBOs), instead of Begin/glVertex2d/End which is deprecated
Try this:
#include <GL/glut.h>
#include <cmath>
float posX = 0, posY = -0.1, posZ = 0;
GLfloat rotation = 90.0;
double x, y, angle;
#define PI 3.1415926535898
GLint circle_points = 50;
void point()
{
glColor3f(0.0, 0.0, 1.0);
glPointSize(11.0);
glBegin(GL_POINTS);
glVertex3f(0.1, 0.1, 0.0);
glEnd();
}
void circ()
{
glColor3f(0.0, 0.0, 1.0);
glBegin(GL_TRIANGLE_FAN);
for (int i = 0; i <= 300; i++)
{
angle = 2 * PI * i / 300;
x = cos(angle) / 20;
y = sin(angle) / 20;
glVertex2d(x, y);
}
glEnd();
}
void display()
{
glClearColor(1.0, 1.0, 1.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
point();
glPopMatrix();
glPushMatrix();
glTranslatef(posX, posY, posZ);
circ();
glPopMatrix();
glutSwapBuffers();
}
float move_unit = 0.02f;
void keyboardown(int key, int x, int y)
{
switch (key)
{
case GLUT_KEY_RIGHT:
posX += move_unit;
break;
case GLUT_KEY_LEFT:
posX -= move_unit;
break;
case GLUT_KEY_UP:
posY += move_unit;
break;
case GLUT_KEY_DOWN:
posY -= move_unit;
break;
default:
break;
}
glutPostRedisplay();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(600, 500);
glutInitWindowPosition(0, 0);
glutCreateWindow("Practice 1");
glutDisplayFunc(display);
glutSpecialFunc(keyboardown);
glutMainLoop();
}
this is my cube. Once created, it has a random x position on either -2, -1, 0, 1, or 2.
void cube(void)
{
srand (time(0));
int cube_posX;
int lowv = -2;
int highv = 2;
cube_posX = rand() % (highv - lowv + 1) + lowv;
glTranslatef(cube_posX, 0.0, cube_angle);
glRotatef(cube_angle, 90.0, 0.0, 1.0);
glutSolidCube(0.25);
}
and this is how I move the cube slowly forward
void MOVE_CUBE(int value)
{
cube_posZ = cube_posZ - 0.01;
glutPostRedisplay();
glutTimerFunc(25, MOVE_CUBE, 0);
}
and finally putting them in display:
void init(void)
{
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}
float cam_eyeX = 0.0, cam_eyeY = 1.5, cam_eyeZ = 5.0;
float cam_centerX = 0.0, cam_centerY = 0.0, cam_centerZ = 0.0;
void display(void)
{
glClearColor(1.0,1.0,1.0,1.0); //to add background color (white)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluLookAt(cam_eyeX, cam_eyeY, cam_eyeZ, cam_centerX, cam_centerY, cam_centerZ, 0.0, 1.0, 0.0); //camera! (cam position X, cam position Y, cam position Z, cam target X, cam target Y, cam target Z, up position X, up position Y, up position Z)
cube();
glutSwapBuffers();
angle += 0.05; //to affect the glRotate function
glFlush();
}
void reshape(int w, int h)
{
glViewport (0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
glMatrixMode (GL_MODELVIEW);
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH); // Set up display buffer
glutInitWindowSize(750, 500); //window's size
glutInitWindowPosition(100, 100); //window's position
glutCreateWindow("Hendra Ganteng!"); //window's title
init();
glutDisplayFunc(display);
glutIdleFunc (display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard_Handler);
MOVE_CUBE(0);
glutMainLoop();
return 0;
}
But when I see it in action, the cube moves forward flawlessly, but keeps changing x position onto those 5 possibilities (-2,-1,0,1,2) every 0.5 to 1 second. If I disable the srand(time(0)), the cube changes its x position rapidly. I just want to make it stay in 1 x position so then I can call more cubes in different x position. Could someone please kindly what's wrong in my code?
How is that behaviour not expected? You are generating a random X position every time you display your cube. If you re-seed the random number generator using the time, then it will be start a different sequence whenever the time changes (once per second).
Instead, you should pre-generate your cube(s). How about this:
// Global cube data
struct Cube {
int x;
double angle;
};
vector<Cube> cubes;
const int num_cubes = 1;
// Example initialisation...
void InitCubes()
{
cubes.reserve(num_cubes);
for( int i = 0; i < num_cubes; i++ )
{
Cube cube;
cube.x = rand() % (highv - lowv + 1) + lowv;
cube.angle = 0.0;
cubes.push_back(cube);
}
}
Now the update/display cycles simply need to modify the angle, but not the x-position.
void UpdateCube( Cube & cube )
{
cube.angle += 0.05;
}
void DisplayCube( Cube & cube )
{
glTranslatef((double)cube.x, 0.0, cube.angle);
glRotatef(cube.angle, 90.0, 0.0, 1.0);
glutSolidCube(0.25);
}
In your main function, call InitCubes() during startup.
In your display function, do this:
void display(void)
{
glClearColor(1.0,1.0,1.0,1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluLookAt(cam_eyeX, cam_eyeY, cam_eyeZ, cam_centerX, cam_centerY, cam_centerZ, 0.0, 1.0, 0.0);
// Display cubes
for( int i = 0; i < cubes.size(); i++ ) DisplayCube( cubes[i] );
glutSwapBuffers();
glFlush();
// Update cubes for next render cycle.
for( int i = 0; i < cubes.size(); i++ ) UpdateCube( cubes[i] );
}