在opengl中将金字塔更改为四面体

问题描述

首先，我对 openGL 很陌生，所以我还不知道所有“基本”的东西。我在一本书中做这个练习，我已经能够画一个金字塔，但我现在想画一个四面体。但我似乎无法理解它。我总是以奇怪或不完整的形状结束。如果我还没有做任何其他事情，请告诉我。 这是代码。任何帮助表示赞赏。

    float pt1 = 1.0f;
    float pt2 = 0.0f;
    glBegin(GL_TRIANGLES);
    // Front
    glColor3f(1.0f,0.0f,0.0f);     // Red
    glVertex3f(pt2,pt1,pt2);
    glVertex3f(-pt1,-pt1,pt1);
    glVertex3f(pt1,pt1);

    // Right
    glColor3f(0.0f,1.0f);     // Blue
    glVertex3f(pt2,pt2);
    glVertex3f(pt1,-pt1);

    // Back
    glColor3f(0.0f,1.0f,0.0f);     // Green
    glVertex3f(pt2,-pt1);
    glVertex3f(-pt1,-pt1);

    // Left
    glColor3f(1.0f,0.0f);       // Yellow
    glVertex3f(pt2,pt1);
    glEnd();

解决方法

Tetrahedron 由 4 个顶点组成：

const float s_8_9 = sqrt(0.8f / 0.9f); // = 0.9428f
const float s_2_9 = sqrt(0.2f / 0.9f); // = 0.4714f
const float s_2_3 = sqrt(0.2f / 0.3f); // = 0.8165f

float vertices[4][3] = {
    { 0.0f,0.0f,1.0f },{ s_8_9,-1.0f / 3.0f},{-s_2_9,s_2_3,-s_2_3,};

顶点形成 4 个三角形面：

int indices[4][3] = {{0,2,1},{0,3,2},{1,0},3}};

使用 vertices 和 indices 绘制四面体：

glBegin(GL_TRIANGLES);

// Front
glColor3f(1.0f,0.0f);     // Red
for (int i = 0; i < 3; i++)
    glVertex3fv(vertices[indices[0][i]]);

// Right
glColor3f(0.0f,1.0f);     // Blue
for (int i = 0; i < 3; i++)
    glVertex3fv(vertices[indices[1][i]]);

// Back
glColor3f(0.0f,1.0f,0.0f);     // Green
for (int i = 0; i < 3; i++)
    glVertex3fv(vertices[indices[2][i]]);

// Left
glColor3f(1.0f,0.0f);     // Yellow
for (int i = 0; i < 3; i++)
    glVertex3fv(vertices[indices[3][i]]);