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我有一个 txt 文件，其中的数据是顶部旋转的质心位置的时间函数（在 3D 中）。所以我想用一个圆锥体来表示这个顶部，我拥有的数据应该代表圆锥体基础的中心，及时围绕顶点旋转。

我有一个代表圆锥体的代码，我设法解决了如何围绕底座旋转它。但是我没有设法围绕它的 Vertex 旋转它。我也不知道如何用我的数据移动圆锥。

#include <GL\glut.h>

GLfloat xRotated, yRotated, zRotated;
// Cone
GLdouble base=1;
GLdouble height=1.5;
GLint slices =50;
GLint stacks =50;


void displayCone(void)
{
    glMatrixMode(GL_MODELVIEW);
    // clear the drawing buffer.
    glClear(GL_COLOR_BUFFER_BIT);
    // clear the identity matrix.
    glLoadIdentity();
    // traslate the draw by z = -4.0
    // Note this when you decrease z like -8.0 the drawing will looks       far , or smaller.
    glTranslatef(0.0,0.0,-4.5);
    // Red color used to draw.
    glColor3f(0.8, 0.2, 0.1); 
    // changing in transformation matrix.
    // rotation about X axis
    glRotatef(xRotated,1.0,0.0,0.0);
    // rotation about Y axis
    glRotatef(yRotated,0.0,1.0,0.0);
    // rotation about Z axis
    glRotatef(zRotated,0.0,0.0,1.0);
    // scaling transfomation 
    glScalef(1.0,1.0,1.0);
    // built-in (glut library) function , draw you a Cone.

    glutSolidCone(base,height,slices,stacks);
    // Flush buffers to screen

    glFlush();        
    // sawp buffers called because we are using double buffering 
    // glutSwapBuffers();
}


void idleCone(void)
{
    xRotated += 0.1;
    yRotated += 0.1;
    zRotated += 0.1; 

    displayCone();
}


int main (int argc, char **argv)
{
    //Initialize GLUT
    glutInit(&argc, argv);
    //double buffering used to avoid flickering problem in animation
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);  
    // window size
    glutInitWindowSize(400,350);
    // create the window 
    glutCreateWindow("Cone Rotating Animation");
    glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
    xRotated = yRotated = zRotated = 30.0;
    xRotated=33;
    yRotated=40;
    glClearColor(0.0,0.0,0.0,0.0);
    //Assign  the function used in events
    glutDisplayFunc(displayCone);
    glutReshapeFunc(reshapeCone);
    glutIdleFunc(idleCone);
    //Let start glut loop
    glutMainLoop();
    return 0;
}

我已经设法用 Gnuplot 表示质心在 3D 中移动，但是用 OpenGL 旋转的圆锥体来做会更漂亮

4

1 回答 1

0

如果要围绕其顶部旋转圆锥体，则必须以这种方式平移圆锥体，使圆锥体的顶部位于原点：

glTranslatef(0.0, 0.0, -height);

这必须在应用旋转和缩放之前完成。由于glTranslate（和其他矩阵变换）将当前矩阵乘以一个新的变换矩阵，glTranslate指令必须在其他模型变换之后完成，例如glRotate和glScale：

void displayCone(void)
{
    glMatrixMode(GL_MODELVIEW);
    // clear the drawing buffer.
    glClear(GL_COLOR_BUFFER_BIT);
    // clear the identity matrix.
    glLoadIdentity();
    // traslate the draw by z = -4.0
    // Note this when you decrease z like -8.0 the drawing will looks       far , or smaller.
    glTranslatef(0.0,0.0,-4.5);
    // Red color used to draw.
    glColor3f(0.8, 0.2, 0.1); 
    // changing in transformation matrix.
    // rotation about X axis
    glRotatef(xRotated,1.0,0.0,0.0);
    // rotation about Y axis
    glRotatef(yRotated,0.0,1.0,0.0);
    // rotation about Z axis
    glRotatef(zRotated,0.0,0.0,1.0);

    // scaling transfomation 
    glScalef(1.0,1.0,1.0);
    // built-in (glut library) function , draw you a Cone.

    // move the peak of the cone to the origin
    glTranslatef(0.0, 0.0, -height);

    glutSolidCone(base,height,slices,stacks);
    // Flush buffers to screen

    glFlush();        
    // sawp buffers called because we are using double buffering 
    // glutSwapBuffers();
}

根据评论扩展：

您能否添加一个简短的代码来帮助我理解如何使用存储在数组中的数据来旋转圆锥体？

了解如何在 C++ 中使用 ifstream逐行读取文件。在以下示例中，将数据存储到 a std::vector，其中每个元素由std::array3组成GLfloat： 

#include <vector>
#include <array>
#include <fstream>
#include <string>
#include <sstream>

void ReadData( const char *fileName, std::vector<std::array<GLfloat, 3>> &data )
{
    std::ifstream dataFile(fileName);
    std::string line;
    while (std::getline(dataFile, line))
    {
        std::istringstream insstr(line);
        GLfloat x, y, z;
        if (!(insstr >> x >> y >> z))
            break; // reading error

        data.push_back( { x, y, z } );
    }
}

读取数据并通过索引访问 3 个角度（例如j）：

std::vector<std::array<GLfloat, 3>> data;

ReadData( "mydata.txt", data );

xRotated = data[j][0];
yRotated = data[j][1];
zRotated = data[j][2];
于 2019-05-19T12:20:27.937 回答