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I draw many lines to form a grid. I want to see the grid rotated on its X-axis, but I never get the intended result. I tried glRotatef and gluLookAt which does not work the way I want. Please see the pictures below.
this is the grid
this is how I want to see it
Edit: geez, posting the code here is also hard, lol, anyway here it is.
Edit2: removed, only leave the code that has issues.
Please find the code below, no matter how I set the gluLookAt, the grid result won't be in the perspective I want.
#include <GL/glut.h>
void display() {
...
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);
for (int i = 0; i < 720; i += 3)
{
glColor3f(0, 1, 1);
glVertex3f(linePoints[i], linePoints[i + 1], linePoints[i + 2]);
}
glEnd();
glFlush();
}
void init() {
glClearColor(0.0, 0.0, 0.0, 1.0);
glColor3f(1.0, 1.0, 1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, 4.0 / 3.0, 1, 40);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0, -2, 1.25, 0, 0, 0, 0, 1, 0);
}
Lets assume, that you have a grid in the xy plane of the world:
glColor3f(0, 1, 1);
glBegin(GL_LINES);
for (int i = 0; i <= 10; i ++)
{
// horizontal
glVertex3f(-50.0f + i*10.0f, -50.0f, 0.0f);
glVertex3f(-50.0f + i*10.0f, 50.0f, 0.0f);
// vertical
glVertex3f(-50.0f, -50.0f + i*10.0f, 0.0f);
glVertex3f( 50.0f, -50.0f + i*10.0f, 0.0f);
}
glEnd();
Ensure that the distance of to the far plane of the projection is large enough (see gluPerspective). All the geometry which is not in between the near an far plane of the Viewing frustum is clipped.
Further more ensure that the aspect ratio (4.0 / 3.0) match the ratio of the viewport rectangle (window).
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, 4.0 / 3.0, 1, 200);
For the use of gluLookAt, the up vector of the view has to be perpendicular to the grid. If the grid is arranged parallel to the xy plane, then the up vector is z axis (0, 0, 1).
The target (center) is the center of the grid (0, 0, 0).
The point of view (eye position) is ought to be above and in front of the grid, for instance (0, -55, 50). Note the point of view is used for a grid with the bottom left of (-50, -50, 0) and a top right of (50, 50, 0).
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0, -55.0, 50.0, 0, 0, 0, 0, 0, 1);
I'm attempting to draw an eclipse-shaped object so I used a sphere and scaled it as necessary. I'm attempting to rotate this eclipse-shaped object with the following code but it won't budge (or at least it doesn't look like it's budging). I've tested by simply changing to another 3D shape and it rotates. Is there something I'm doing wrong? What's so different about a glutSolidSphere?
glPushMatrix();
glTranslatef(subx, suby + y, subz);
glScalef(9.0, 1.75, 1.75);
glRotatef(angle, 0, 1, 0);
glTranslatef(-subx, -suby, -subz);
glTranslatef(subx, suby, subz);
glutSolidSphere(1.0, 50, 50);
glPopMatrix();
Issue as pointed out above in comments was that I was rotating the sphere before I stretched it. Scaling and then rotating fixed the issue.
glPushMatrix();
glTranslatef(subx, suby + y, subz);
glRotatef(angle, 0, 1, 0);
glScalef(9.0, 1.75, 1.75);
glTranslatef(-subx, -suby, -subz);
glTranslatef(subx, suby, subz);
glutSolidSphere(1.0, 50, 50);
glPopMatrix();
#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 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).
Okay, so my program opens a file, reads in xyz-points, then draws a line strip out of it. I originally had this program written in SharpGL (implemnted as WPF window) and it worked, but not well due to using immediate mode, so I have moved onto OpenGL in C++. I have (somewhat) figured out VBO's and I now I am trying to add mouse functionality now. My problem is I can't move the picture with my mouse, I want to be able to click and 'drag' the picture. My mouseClickFunc and mouseMotion work (my cout statements execute), however it seems like my translate call is never being executed (i.e. the picture starts partially 'clipped' in the scene and I would like the ability to drag it and center it). I know this is a shot in the dark but I am really not sure what to do.
MotionFunc:
void mouseMotion(int x, int y)
{
if (moveable)
{
xMove += xTransform(x) - xTransform(xDown);
yMove += yTransform(y) - yTransform(yDown);
xDown = x;
yDown = y;
cout << yMove << "---" << xMove << endl;
glutSwapBuffers();
glutPostRedisplay();
}
}
Display Function:
void RenderFunction(void)
{
++FrameCount;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glOrtho(xMin - 1, xMax + 1, yMin - 1, yMax + 1, -diameter * zScale, diameter * zScale);
// Reset the modelview matrix.
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glTranslatef(xMove, -yMove, 0);
//glViewport((GLint)xMove*100, (GLint)-yMove*100, CurrentWidth, CurrentHeight);
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, 29000);
glPopMatrix();
glutSwapBuffers();
glutPostRedisplay();
}
I am sure there is more code that I need to show, this is just where I think the problem is. Any help would be greatly appreciated.
Here is a picture of a console output and the screen (OpenGL context) as I see it.
UPDATE: Updated my code. It looks like my coordinates are moving, but the picture is not if that makes sense. If you look at my output, if I keep 'dragging' the picture, you can see in the console that the variable xMove and yMove can get as large or small as they want, again translate is just never moving it.
You pop your matrix before drawing things, which resets the matrix to the state of last push matrix. Move glPopMatrix(); below draw call
You're popping the matrix before you call glDrawArrays(), so this naturally negates the effect of the translation. It also negates the glOrtho() call, but that should be issued on the projection matrix and not on the modelview matrix in the first place.
And, of course, the problem is in your code, and not in OpenGL.
In this code excerpt :
glLoadIdentity();
glPushMatrix();
glTranslatef(xMove, -yMove, 0);
//glViewport((GLint)xMove*100, (GLint)-yMove*100, CurrentWidth, CurrentHeight);
glOrtho(xMin - 1, xMax + 1, yMin - 1, yMax + 1, -diameter * zScale, diameter * zScale);
glPopMatrix();
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, 29000);
you are :
setting the identity as the view matrix
push it into the queue
modify it by glTranslate
pop it of the stack
render the image
Therefore, your translation is ignored.
This is correct operation :
glLoadIdentity();
glPushMatrix();
glTranslatef(xMove, -yMove, 0);
//glViewport((GLint)xMove*100, (GLint)-yMove*100, CurrentWidth, CurrentHeight);
glOrtho(xMin - 1, xMax + 1, yMin - 1, yMax + 1, -diameter * zScale, diameter * zScale);
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, 29000);
glPopMatrix();
You are multiplying projection before translation, remember to always read matrix transformation from bottome to top in OpenGL 1.1 which you should upgrade IMO. Another issue is that you are poping the matrix before drawing.
Correct code:
//glViewport((GLint)xMove*100, (GLint)-yMove*100, CurrentWidth, CurrentHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(xMin - 1, xMax + 1, yMin - 1, yMax + 1, -diameter * zScale, diameter * zScale);
// Reset the modelview matrix.
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();
glTranslatef(xMove, -yMove, 0);
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_LINE_STRIP, 0, 29000);
glPopMatrix();