OpenGL中立方体的位置

Posted 2023-02-22

【中文标题】OpenGL中立方体的位置

【英文标题】：Location of cube in OpenGL

【发布时间】：2019-11-03 09:56:20

【问题描述】：

这段代码的输出是 25 个小熊旋转。 我面临的问题是每个立方体的位置，我不知道如何使它们排成一行，例如每 5 个立方体排成一行等等。

注意：我已经添加了立方体的位置。

glm::vec3 cubePositions[] = 
    glm::vec3(0.0f,  0.0f,  0.0f),
    glm::vec3(2.0f,  5.0f, -15.0f),
    glm::vec3(-1.5f, -2.2f, -2.5f),
    glm::vec3(-3.8f, -2.0f, -12.3f),
    glm::vec3(2.4f, -0.4f, -3.5f),
    glm::vec3(-1.7f,  3.0f, -7.5f),
    glm::vec3(1.3f, -2.0f, -2.5f),
    glm::vec3(1.5f,  2.0f, -2.5f),
    glm::vec3(1.5f,  0.2f, -1.5f),
    glm::vec3(-1.3f,  1.0f, -1.5f)
;

while (!glfwWindowShouldClose(mainWindow))

    glfwPollEvents();

    glClearColor(0.0f, 0.1f, 0.2f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //Camera transformation
    glm::mat4 projection = glm::mat4(1.0f);
    glm::mat4 view = glm::mat4(1.0f);
    projection = glm::perspective(glm::radians(45.0f), (float)WIDTH / (float)HEIGHT, 0.1f, 100.0f);
    view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));

    //Get uniform locations
    GLint viewlLoc = glGetUniformLocation(ourShader.Program, "view");
    glUniformMatrix4fv(viewlLoc, 1, GL_FALSE, glm::value_ptr(view));
    GLint projlLoc = glGetUniformLocation(ourShader.Program, "projection");
    glUniformMatrix4fv(projlLoc, 1, GL_FALSE, glm::value_ptr(projection));

    // Call Shader Program
    ourShader.Use();

    glBindVertexArray(VAO);

    for(unsigned int i = 0; i < 25; i++)
    
        glm::mat4 model = glm::mat4(1.0f);
        model = glm::translate(model, cubePositions[i]);
        float angle = 20.0f * i;
        angle = glfwGetTime() * 25.0f;
        model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
        GLint modelLoc = glGetUniformLocation(ourShader.Program, "model");
        glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));

        glDrawArrays(GL_TRIANGLES, 0, 36);
    

    glBindVertexArray(0);

    glfwSwapBuffers(mainWindow);
    glfwPollEvents();

【问题讨论】：

什么是cubePositions[i]转换矩阵model = glm::translate(model, cubePositions[i]);的计算行？

【参考方案1】：

使用glm::translate 为每个单独的立方体的模型矩阵添加转换，具体取决于立方体的索引。例如：

for(unsigned int i = 0; i < 25; i++)

    float dist = ; // distance between the cubes
    float x = (i % 5) * dist;
    float y = (i / 5) * dist;

    float angle = 20.0f * i;
    angle = glfwGetTime() * 25.0f;

    glm::mat4 model = glm::mat4(1.0f);
    model = glm::translate(model, glm::vector3(x, y, 0.0f));
    model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));

    GLint modelLoc = glGetUniformLocation(ourShader.Program, "model");
    glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));

    glDrawArrays(GL_TRIANGLES, 0, 36);

注意，您必须定义立方体之间的距离 (dist)。

---

注意，矩阵的串联（乘法*）不是Commutative。 如果要旋转整个立方体块，则必须在旋转之前进行平移：

model = rotate * translate

由于glm::rotate分别为glm::translate，定义一个矩阵并将输入矩阵乘以新矩阵，glm::rotate必须在glm::translate之前完成：

glm::mat4 model = glm::mat4(1.0f);
model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
model = glm::translate(model, glm::vector3(x, y, 0.0f));

---

您可以使用算法计算cubePositions：

#include <vector>

std::vector<glm::vec3> cubePositions;
for(unsigned int i = 0; i < 25; i++)

    float dist = 5.0f; // distance between the cubes
    float x = (i % 5) * dist;
    float y = (i / 5) * dist;
    cubePositions.push_back(glm::vec3(x, y, 0.0f));

【讨论】：

我添加了 cubePositions[i] 让它更清晰。

@Noura 请阅读答案。您必须根据其索引计算立方体的位置。不要使用你困惑的cubePositions。但是你可以计算立方体的位置。请参阅我现在添加的答案的最后一部分。