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c++ - 显示和移动正方形

转载 作者:行者123 更新时间:2023-11-30 04:53:55 25 4
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#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) {
glBegin(GL_POLYGON);
glColor3f(1.0, 0.0, 0.0); // set colour to red
glVertex2f(162, 50);
glVertex2f(162, 10);
glVertex2f(220, 10);
glVertex2f(220, 50);
glVertex2f(162, 50);
glTranslatef(squareX, squareY, squareZ); // moving it toward the screen a bit on creation
glEnd();
}

void initRendering() {
glEnable(GL_DEPTH_TEST);
}

// called when the window is resized
void handleResize(int w, int h) {
// tell OpenGL how to convert from coordinates to pixel values
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION); // switch to setting the camera perspective
// set the camera perspective
glLoadIdentity(); // reset the camera
gluPerspective(45.0, // the camera angle
(double)w / (double)h, // the width-to-height ratio
1.0, // the near z clipping coordinate
200.0); // the far z clipping coordinate
}

void drawScene() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
drawShape();
glutSwapBuffers();
}

// float _angle = 30.0f;
void update(int value) {
if (flag) {
squareY += 0.001f;
if (squareY > 0.3) {
flag = 0;
}
}
if (!flag) {
squareY -= 0.001f;
if (squareY < -0.3) {
flag = 1;
}
}
glutPostRedisplay(); // tell GLUT that the display has changed
// tell GLUT to call update again in 25 milliseconds
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);
}

我已经在代码中添加了注释,以便您可以理解它。我正在尝试创建一个移动到屏幕顶部的正方形,但我无法显示正方形。出于某种原因,当我运行代码时它没有出现。当我删除移动代码时,我只能显示正方形。如何显示正方形并使其上升?

最佳答案

请注意,几十年来,由 glBegin/glEnd 序列和固定功能流水线矩阵堆栈进行的绘制已被弃用。了解 Fixed Function Pipeline并查看 Vertex SpecificationShader最先进的渲染方式。


无论如何,glTranslatef 不允许出现在glBegin/glEnd 序列中。在 glBegin 之前执行:

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();
}

如果你想在窗口坐标中绘制四边形,那么你必须使用正交投影(glOrtho):

void handleResize(int w, int h) {

glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
/*
gluPerspective(45.0, // the camera angle
(double)w / (double)h, // the width-to-height ratio
1.0, // the near z clipping coordinate
200.0); // the far z clipping coordinate
*/

glOrtho( 0.0f, (float)w, 0.0f,(float)h, -1.0f, 1.0f );
}

并且您必须更改翻译量:

void update(int value) {
if (flag) {
squareY += 1.0f;
if (squareY > 350.0) {
flag = 0;
}
}
if (!flag) {
squareY -= 1.0f;
if (squareY < 0.0) {
flag = 1;
}
}
glutPostRedisplay();
glutTimerFunc(25, update, 0);
}

预览:

关于c++ - 显示和移动正方形,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/53749750/

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