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OpenGL learning (III) glut two-dimensional image rendering
2022-07-24 18:46:00 【Pony Baby】
List of articles
1.Opengl Of Hello world
The most basic program , I drew a triangle , Please make sure you understand this procedure , The core is opengl Is a state machine . Think opengl It's a geometric sketchpad ,glBegin(GL_TRIANGLES); Click to draw triangle .glColor3f(1.0, 0.0, 0.0); Is to set the color to red . Then you point three points at three different positions .glFlush(); Save and submit to the screen . Then you get the result .
#include <gl/glut.h>
// When the window changes （ Such as changing the size ） Automatically call
void mydisplay()
{
// Clear color cache
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
// Two dimensional can also be used glVertex2f
// The first point is red
glColor3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
// Second, green
glColor3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
// The third point is blue
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
glFlush();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
// Initialize window name
glutCreateWindow("A Triangle");
// binding display function
glutDisplayFunc(mydisplay);
// Open window loop
glutMainLoop();
return 0;
}
2. initialization （ Adjustment attempt ）
Manually set the use RGB draw 、 Window position and size . And in init Function has been added glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0); Turn the image into the image (x,y,z) Respectively corresponding to the range (0-1,0-1,0-1) Section .
#include <gl/glut.h>
// When the window changes （ Such as changing the size ） Automatically call
void mydisplay()
{
// Clear color cache
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
// Two dimensional can also be used glVertex2f
// The first point is red
glColor3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
// Second, green
glColor3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
// The third point is blue
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
glFlush();
}
void init()
{
// The full screen color turns black
glClearColor(0.0, 0.0, 0.0, 1.0);
// Change the projection view ,
glMatrixMode(GL_PROJECTION);
//opengl Is a state machine , First clear the previous transformation matrix data , Therefore, each perspective operation must first be changed into an identity matrix
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
//GLUT_RGB Refers to the use RGB Drawing
glutInitDisplayMode(GLUT_RGB);
// Initialize window size
glutInitWindowSize(100, 100);
// Initialize window position
glutInitWindowPosition(100, 100);
// Set window name
glutCreateWindow("A Triangle");
// binding display function
glutDisplayFunc(mydisplay);
// Set up opengl The initial state
init();
// Open window loop
glutMainLoop();
return 0;
}
3. increase Reshape function
The function that will be called when changing the window . default reshape Function will stretch the graph directly .
We want the image not to be stretched , But keep the original size .
#include <gl/glut.h>
// Initial window size
int initW = 300;
int initH = 300;
// When the window changes （ Such as changing the size ） Automatically call
void mydisplay()
{
// Clear color cache
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
// Two dimensional can also be used glVertex2f
// The first point is red
glColor3f(1.0, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
// Second, green
glColor3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
// The third point is blue
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
glFlush();
}
// Initialization function , Generally, it includes perspective, etc
void init()
{
// The full screen color turns black
glClearColor(0.0, 0.0, 0.0, 1.0);
// Change the projection view ,
glMatrixMode(GL_PROJECTION);
//opengl Is a state machine , First clear the previous transformation matrix data
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
}
// Data called when the window size is changed
void myReshape(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho(0, 1.0, 0.0, (GLfloat)h / (GLfloat)w * 1.0, 0.0, 1.0);
else
glOrtho(0, (GLfloat)w / (GLfloat)h * 1.0, 0.0, 1.0, 0.0, 1.0);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
//GLUT_RGB Refers to the use RGB Drawing
glutInitDisplayMode( GLUT_RGB);
// Initialize window size
glutInitWindowSize(initW, initH);
// Initialize window position
glutInitWindowPosition(100, 100);
// Set window name
glutCreateWindow("A Triangle");
// binding display function
glutDisplayFunc(mydisplay);
// Set up opengl The initial state
init();
// Bind the function called when changing the window size
glutReshapeFunc(myReshape);
// Open window loop
glutMainLoop();
return 0;
}
3. event
Added left mouse click event mouse, Clicking will change the brightness of the image and output the click position
#include <gl/glut.h>
#include <iostream>
// Initial window size
int initW = 300;
int initH = 300;
// Color brightness
GLfloat brightness = 1.0;
GLfloat increment = -0.1;
// When the window changes （ Such as changing the size ） Automatically call
void mydisplay()
{
// Clear color cache
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
// Two dimensional can also be used glVertex2f
// The first point is red
glColor3f(brightness, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
// Second, green
glColor3f(0.0, brightness, 0.0);
glVertex3f(0.0, 1.0, 0.0);
// The third point is blue
glColor3f(0.0, 0.0, brightness);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
glFlush();
}
// Initialization function , Generally, it includes perspective, etc
void init()
{
// The full screen color turns black
glClearColor(0.0, 0.0, 0.0, 1.0);
// Change the projection view ,
glMatrixMode(GL_PROJECTION);
//opengl Is a state machine , First clear the previous transformation matrix data
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
}
// Data called when the window size is changed
void myReshape(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho(0, 1.0, 0.0, (GLfloat)h / (GLfloat)w * 1.0, 0.0, 1.0);
else
glOrtho(0, (GLfloat)w / (GLfloat)h * 1.0, 0.0, 1.0, 0.0, 1.0);
}
// Mouse events
void mouse(int btn, int state, int x, int y)
{
// Left click mouse , Adjust the brightness of the image
if (btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{
// Output location , Note that the origin of the mouse is in the upper left corner , The image origin is in the lower right corner , therefore y It's the opposite
std::cout << "x: " << x << " y: " << y << std::endl;
// Change the brightness
brightness += increment;
if (brightness >= 1.0 || brightness <= 0.0)
increment = -increment;
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
//GLUT_RGB Refers to the use RGB Drawing
glutInitDisplayMode( GLUT_RGB);
// Initialize window size
glutInitWindowSize(initW, initH);
// Initialize window position
glutInitWindowPosition(100, 100);
// Set window name
glutCreateWindow("A Triangle");
// binding display function
glutDisplayFunc(mydisplay);
// Set up opengl The initial state
init();
// Bind the function called when changing the window size
glutReshapeFunc(myReshape);
// Bind mouse events
glutMouseFunc(mouse);
// Open window loop
glutMainLoop();
return 0;
}
4. Animation
An animation using a timer , Image brightness changes with time
#include <gl/glut.h>
#include <iostream>
// Initial window size
int initW = 300;
int initH = 300;
// Color brightness
GLfloat brightness = 1.0;
GLfloat increment = -0.1;
// When the window changes （ Such as changing the size ） Automatically call
void mydisplay()
{
// Clear color cache
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_TRIANGLES);
// Two dimensional can also be used glVertex2f
// The first point is red
glColor3f(brightness, 0.0, 0.0);
glVertex3f(1.0, 0.0, 0.0);
// Second, green
glColor3f(0.0, brightness, 0.0);
glVertex3f(0.0, 1.0, 0.0);
// The third point is blue
glColor3f(0.0, 0.0, brightness);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
// Use DOUBLE_BUFFER after , Use the following code to swap the front and back memory
glutSwapBuffers();
}
// Functions called by timer
void changeColor(int x)
{
// Change the brightness
brightness += increment;
if (brightness >= 1.0 || brightness <= 0.0)
increment = -increment;
// Call again immediately display function , Otherwise, the image will not be drawn immediately
glutPostRedisplay();
// Set a new timer
glutTimerFunc(100, changeColor, 0);
}
// Initialization function , Generally, it includes perspective, etc
void init()
{
// The full screen color turns black
glClearColor(0.0, 0.0, 0.0, 1.0);
// Change the projection view ,
glMatrixMode(GL_PROJECTION);
//opengl Is a state machine , First clear the previous transformation matrix data
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
//GLUT_DOUBLE Double cache , Usually used in animation , It can make the animation smoother
//GLUT_RGB Refers to the use RGB Drawing
glutInitDisplayMode( GLUT_RGB|GLUT_DOUBLE);
// Initialize window size
glutInitWindowSize(initW, initH);
// Initialize window position
glutInitWindowPosition(100, 100);
// Set window name
glutCreateWindow("A Triangle");
// Set the timing function
glutTimerFunc(10, changeColor, 0);
// binding display function
glutDisplayFunc(mydisplay);
// Set up opengl The initial state
init();
// Open window loop
glutMainLoop();
return 0;
}
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