I am making 3d open gl project which contain camera object as a shooting bullet but it is render with very big size and contain whole screen in white lines like this
i want to display object as a center of camera with small size how to do this
code is here
static GLdouble ort1[] = { -200, 200, -33, 140 };
static GLdouble viewer[] = { 525, 25, -180 };
static GLdouble up[] = { 0, 1, 0 };
static GLdouble objec[] = { 525.0, 25, -350 };
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
gluLookAt(viewer[0], viewer[1], viewer[2], objec[0], objec[1], objec[2], 0, 1, 0);
glMatrixMode(GL_PROJECTION);
//glOrtho(-1, 1, -1, 1, -1, 100);
glLoadIdentity();
//gluPerspective(fov, 1.333, n, f);
gluPerspective(fov, 1, 0.001, 1000);
//gluPerspective(50, screenWidth / screenHeight, 0.000001, 2000);
glPointSize(2.0);
glMatrixMode(GL_MODELVIEW);
//cube.drawFace(10, 20, 10, 22);
drawFlorr();
glPushMatrix();
glTranslatef(viewer[0], viewer[1], viewer[2]); // Translation to the camera center
glRotatef(camAngle * 57.2957795, 0, 1, 0); // Rotate to correspond to the camera
//glTranslatef(0.016, 0, -0.05); // Offset to draw the object
glutWireCone(0.005, 1, 20, 20);
glPopMatrix();
i am new in game prgramming and stuck in this problem ?
You're not setting up the projection matrix correctly.
You need to set the mode to GL_PROJECTION, then set the projection matrix to look at the target (shooter's object of attention) and have a perspective correct with right field of view.
Then set the modelview matrix, mode GL_MODELVIEW.
The gun sight needs to be placed so that it is looking at the camera, and the camera is looking at it. So on the line between the shooter's eyes and his object of attention, perpendicular to it. Do this in the modelview matrix, and call gluLookAt again, on the model.
(Ultimately projection and modelview get multiplied, but Open GL handles that for you).
Related
I tried to draw a teapot and view it in 3D but when I ran the program, nothing showed up. There is nothing in the window. I know it has something to do with my gluLookAt() function but I am not sure how to fix it.
// helloteapot.cc
//#include <GLUT/gl.h>
#include <GLUT/glut.h>
#include "GL/glui.h"
void display () {
/* clear window */
glClear(GL_COLOR_BUFFER_BIT);
/* draw scene */
glColor3f(1.0, 0.0, 0.0);
glTranslatef(0.0, 0.5, 0.0);
glutSolidTeapot(0.15);
/* flush drawing routines to the window */
glFlush();
}
int main ( int argc, char * argv[] ) {
glutInit(&argc,argv);
/* setup the size, position, and display mode for new windows */
glutInitWindowSize(800,600);
glutInitWindowPosition(0,0);
glutInitDisplayMode(GLUT_RGB);
/* create and set up a window */
glutCreateWindow("hello, teapot!");
glutDisplayFunc(display);
/*GLfloat width = 800;
GLfloat height = 600;
GLfloat aspect = (GLfloat)width / (GLfloat)height;
// Set the viewport to cover the new window
glViewport(0, 0, width, height);*/
// Set the aspect ratio of the clipping volume to match the
viewport
glMatrixMode(GL_PROJECTION); // To operate on the Projection
matrix
glLoadIdentity(); // Reset
// Enable perspective projection with fovy, aspect, zNear and zFar
//luPerspective(45.0f, aspect, -100.0f, 100.0f);
gluLookAt(0, 0, 0, 0, 0.5, 0, 0, -1, 0);
/* tell GLUT to wait for events */
glutMainLoop();
}
You have asked GL to position the camera at the origin, aim the camera upwards towards the point (0, 0.5, 0), and have also specified (incorrectly) the up vector to be 0, -1, 0. The problem is that the camera's forward direction is (0, 1, 0) [as specified by your eye and aim positions], and this direction conflicts with the up vector or (0, -1, 0). Try using a vector at right angles to the forward direction instead! (e.g. [1, 0, 0], [0, 0, 1])
gluLookAt(
0, 0, 0, //< camera location
0, 0.5, 0, //< looking towards point
1, 0, 0); //< which direction is up?
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<GL/glut.h>
double cameraAngle;
void grid_and_axes() {
// draw the three major AXES
glBegin(GL_LINES);
//X axis
glColor3f(0, 1, 0); //100% Green
glVertex3f(-150, 0, 0);
glVertex3f(150, 0, 0);
//Y axis
glColor3f(0, 0, 1); //100% Blue
glVertex3f(0, -150, 0); // intentionally extended to -150 to 150, no big deal
glVertex3f(0, 150, 0);
//Z axis
glColor3f(1, 1, 1); //100% White
glVertex3f(0, 0, -150);
glVertex3f(0, 0, 150);
glEnd();
//some gridlines along the field
int i;
glColor3f(0.5, 0.5, 0.5); //grey
glBegin(GL_LINES);
for (i = -10; i <= 10; i++) {
if (i == 0)
continue; //SKIP the MAIN axes
//lines parallel to Y-axis
glVertex3f(i * 10, -100, 0);
glVertex3f(i * 10, 100, 0);
//lines parallel to X-axis
glVertex3f(-100, i * 10, 0);
glVertex3f(100, i * 10, 0);
}
glEnd();
}
void display() {
//codes for Models, Camera
//clear the display
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0, 0, 0, 0); //color black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //clear buffers to preset values
/***************************
/ set-up camera (view) here
****************************/
//load the correct matrix -- MODEL-VIEW matrix
glMatrixMode(GL_MODELVIEW); //specify which matrix is the current matrix
//initialize the matrix
glLoadIdentity(); //replace the current matrix with the identity matrix [Diagonals have 1, others have 0]
//now give three info
//1. where is the camera (viewer)?
//2. where is the camera looking?
//3. Which direction is the camera's UP direction?
//gluLookAt(0,-150,20, 0,0,0, 0,0,1);
gluLookAt(150 * sin(cameraAngle), -150 * cos(cameraAngle), 50, 0, 0, 0, 0, 0, 1);
/*************************
/ Grid and axes Lines
**************************/
grid_and_axes();
/****************************
/ Add your objects from here
****************************/
/*glColor3f(1, 0, 0);
glutSolidCone(20, 20, 20, 20);
glColor3f(0, 0, 1);
GLUquadricObj *cyl = gluNewQuadric();
gluCylinder(cyl, 10, 10, 50, 20, 20);
glTranslatef(0, 0, 50);
glColor3f(1, 0, 0);
glutSolidCone(10, 20, 20, 20);
*/
glColor3f(1, 0, 0);
glutSolidCube(1);
I am not getting any cube here.
However if I use any transformation property like scaling or rotate then I get the desired cube like
glColor3f(1, 0, 0);
glScalef(50,5,60);
glutSolidCube(1);
what is the problem?
Another problem I am facing that color doesn't work if i don't use transformation property like above mentioned. If I write:
glColor3f(1, 0, 0);
glutSolidCone(20, 20, 20, 20);
For above codes color doesn't work; i get the default colored cone
However if I change this two lines to these 3 lines then color works perfectly:
glColor3f(1,0,0);
glTranslatef(0, 0, 50);
glutSolidCone(10,20,20,20);
then color works; what is the problem? Please help
//ADD this line in the end --- if you use double buffer (i.e. GL_DOUBLE)
glutSwapBuffers();
}
void animate() {
//codes for any changes in Models, Camera
cameraAngle += 0.001; // camera will rotate at 0.002 radians per frame.
//codes for any changes in Models
//MISSING SOMETHING? -- YES: add the following
glutPostRedisplay(); //this will call the display AGAIN
}
void init() {
//codes for initialization
cameraAngle = 0; //angle in radian
//clear the screen
glClearColor(0, 0, 0, 0);
/************************
/ set-up projection here
************************/
//load the PROJECTION matrix
glMatrixMode(GL_PROJECTION);
//initialize the matrix
glLoadIdentity();
/*
gluPerspective() — set up a perspective projection matrix
fovy - Specifies the field of view angle, in degrees, in the y direction.
aspect ratio - Specifies the aspect ratio that determines the field of view in the x direction. The aspect ratio is the ratio of x (width) to y (height).
zNear - Specifies the distance from the viewer to the near clipping plane (always positive).
zFar - Specifies the distance from the viewer to the far clipping plane (always positive).
*/
gluPerspective(70, 1, 0.1, 10000.0);
}
int main(int argc, char **argv) {
glutInit(&argc, argv); //initialize the GLUT library
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
/*
glutInitDisplayMode - inits display mode
GLUT_DOUBLE - allows for display on the double buffer window
GLUT_RGBA - shows color (Red, green, blue) and an alpha
GLUT_DEPTH - allows for depth buffer
*/
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGB);
glutCreateWindow("Some Title");
init(); //codes for initialization
glEnable(GL_DEPTH_TEST); //enable Depth Testing
glutDisplayFunc(display); //display callback function
glutIdleFunc(animate); //what you want to do in the idle time (when no drawing is occuring)
glutMainLoop(); //The main loop of OpenGL
return 0;
}
I am not getting any cube here.
You do get a cube. It is just that tiny speck where the axis intersect. What else would you expect to see when you draw something 2 units big, ~160 units away, with a 70 degree field of view?
Another problem I am facing that color doesn't work if i don't use transformation property like above mentioned.
[...] I get the default colored cone.
I've no idea what you even mean by that. The "default color" would be the initial value of GL's builtin color attribute - which is (1, 1, 1, 1) - white. With the code you have set up, you will get the color which you set before. So the only guess I can make here is that you confused yourself by not properly taking GL's state machine into account.
But besides all that, you should not use that code at all - this is using the fixed function pipeline and immediate mode drawing - features which are deprecated since a decade now, and not supported at all by modern core profiles of OpenGL. Trying to learn that stuff in 2017 is a waste of time. And btw:
glutMainLoop(); //The main loop of OpenGL
Nope. Just NO!!!. OpenGL does not have a "main loop". GLUT is not OpenGL. Honestly, this is all just horrible.
I want to implement a camera that follows my 3D object (a car). To set the camera I use the following structure:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45, 1, -5, 5);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(pos_x + (cos(90)*0.5), pos_y + (0.5*sin(90)), 8, pos_x, pos_y, 6, 0, 1, 0);
//pos are the coordinates of the car
My problem is when I change to that camera, the camera doesn't stay behind the car, just on top of it. Why?
I am having an issue setting up the viewing projection. I am drawing a cube with the vertices (0, 0, 0) (0, 0, 1) (0, 1, 1) (0, 1, 0) (1, 0, 0) (1, 1, 0) (1, 1, 1) and (1, 0, 1). This is how I am initializing the view:
void initGL(int x,int y, int w, int h)
{
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowPosition( x, y );
glutInitWindowSize( w, h );
glutCreateWindow( "CSE328 Project 1" );
glutDisplayFunc(draw);
glFrontFace(GL_FRONT_AND_BACK);
glMatrixMode(GL_PROJECTION);
glFrustum(-10.0, 10.0, -10.0, 10.0, 2.0, 40.0);
glMatrixMode(GL_MODELVIEW);
gluLookAt(10, 10, 10, 0.5, 0.5, 0, 0, 1.0, 0);
glutMainLoop();
}
For some reason, the cube is filling the entire screen. I have tried changing the values of the frustum and lookAt methods, and either the cube is not visible at all, or it fills the entire viewport. In glLookAt I assume the 'eye' is positioned at (10, 10, 10) and looking at the point (0.5, 0.5, 0), which is on the surface of the cube. I thought this would give enough distance so the whole cube would be visible. Am i thinking about this in the wrong way? I have also tried moving the cube in the z direction so that it lies from z = 10 to z = 11, and so is in the clipping plane, but it gives similar results.
The cube has length 1, the viewing volume spans 20 units in x and y dimensions. The cube occupies some pixels in the middle even with orthographic projection; unless there is some other transformation applied during drawing.
I suggest making the frustum smaller (e.g. +/- 2.0f) and moving the camera closer; (4.0f, 4.0f, 4.0f).
Moving the eye position further from the cube by changing the first 3 parameters of gluLookAt() should make it smaller.
You could also replace your call to glFrustum() with a call to gluPerspective() which would make it easier to configure the perspective projection to your liking.
I have some code which draws a line along the x, y and z axes. My problem is that these lines are being clipped so that they are invisible near the origin:
This sounds like a far clipping plane issue, but I gave zFar=50 to gluPerspective, which should be plenty. Making it even larger doesn't seem to help. What else could be causing the clipping?
Here is my code:
import static org.lwjgl.opengl.GL11.*;
import org.lwjgl.opengl.*;
import org.lwjgl.util.glu.GLU;
public class Test {
static int width = 300, height = 200;
public static void main(String[] _) throws Exception {
Display.setDisplayMode(new DisplayMode(width, height));
Display.create();
glClear(GL_COLOR_BUFFER_BIT);
// projection matrix
glMatrixMode(GL_PROJECTION_MATRIX);
glLoadIdentity();
GLU.gluPerspective(50, width / (float) height, .1f, 50);
// modelview matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
GLU.gluLookAt(
.8f, .8f, .8f,
0, 0, 0,
0, 1, 0);
// draw a line for each axis
glBegin(GL_LINES);
// x axis in red
glColor3f(1, 0, 0);
glVertex3i(0, 0, 0);
glVertex3i(10, 0, 0);
// y axis in green
glColor3f(0, 1, 0);
glVertex3i(0, 0, 0);
glVertex3i(0, 10, 0);
// z axis in blue
glColor3f(0, 0, 1);
glVertex3i(0, 0, 0);
glVertex3i(0, 0, 10);
glEnd();
Display.update();
// wait for a close event
while (!Display.isCloseRequested()) {
Thread.sleep(20);
Display.processMessages();
}
Display.destroy();
}
}
Update - Removing glLoadIdentity(); after glMatrixMode(GL_MODELVIEW); gives the desired result, but I don't understand why. Isn't the default modelview matrix the identity matrix?
Update - I wrote a C version of the same code and it works as desired. Why the difference?
Indeed, after testing it, it turns out that glMatrixMode(GL_PROJECTION_MATRIX); should be glMatrixMode(GL_PROJECTION); instead.
So it seems that the modelview was active by default and glLoadIdentity() cleared the results of GLU.gluPerspective(50, width / (float) height, .1f, 50);
edit: Btw. in case you wonder what GL_PROJECTION_MATRIX is for, it's to retrieve the current matrix from the top of the matrix stack with glGetFloatv(GL_PROJECTION_MATRIX,output); or glGetDoublev(GL_PROJECTION_MATRIX,output);