如何使用多个VAO和VBO在OpenGL中绘制多个对象？

Question

我正在尝试使用多个VAO和VBO在OpenGL中渲染多个对象。使用相同的顶点来渲染多个对象，但是我要为每个对象使用不同的顶点，例如绘制一个正方形和一个圆形。对于正方形，我仅需要6个顶点，对于圆形，我需要360。我在读取或创建着色器时出错。

这里是顶点着色器：

#version 330 core

layout (location = 0) in vec4 position;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

void main()
{
    gl_Position = projection * view * model * position;
}

片段着色器：

#version 330 core

layout(location = 0) out vec4 color;

uniform vec4 u_Color;

void main()
{
    color = u_Color;
}

VAO和VBO的生成和绑定

// Circle
std::vector<VertexFormat> vertices;

for (int i = 0; i < 360; i++)
{
    GLfloat angle = i * ((2.0f * 3.14159f) / 360);
    vertices.push_back(VertexFormat(glm::vec3(cos(angle) * 100.0f, sin(angle) * 100.0f, 0.0f)));
}

// Pipette object
std::vector<VertexFormat> pipetteVertices;
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 500.0f, injPipette.y + 500.0f, 0.0f))); // 0
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 700.0f, injPipette.y + 500.0f, 0.0f))); // 1
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 700.0f, injPipette.y + 700.0f, 0.0f))); // 2
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 500.0f, injPipette.y + 700.0f, 0.0f))); // 3
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 500.0f, injPipette.y + 500.0f, 0.0f)));
pipetteVertices.push_back(VertexFormat(glm::vec3(injPipette.x + 700.0f, injPipette.y + 700.0f, 0.0f)));

GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(VertexFormat) * 6, &pipetteVertices[0], GL_STATIC_DRAW);

//Position attribute
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(VertexFormat), (GLvoid *)0);

GLuint vao2;
glGenVertexArrays(1, &vao2);
glBindVertexArray(vao2);

GLuint vbo2;
glGenBuffers(1, &vbo2);
glBindBuffer(GL_ARRAY_BUFFER, vbo2);
glBufferData(GL_ARRAY_BUFFER, sizeof(VertexFormat) * 360, &vertices[0], GL_STATIC_DRAW);

//Position attribute
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(VertexFormat), (GLvoid *) 0);

glBindBuffer(GL_ARRAY_BUFFER, 0);

以及渲染循环中的绘制调用：

    //Get the uniform locations of model, view and projection matrices
    modelID = glGetUniformLocation(program, "model");
    viewID = glGetUniformLocation(program, "view");
    projectionID = glGetUniformLocation(program, "projection");

    //View transform
    glm::mat4 view = glm::lookAt(glm::vec3(0, 0, 2), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
    //Projection transform
    //glm::mat4 projection = glm::perspective(45.0f, (GLfloat)screenWidth / (GLfloat)screenHeight, 0.1f, 1000.0f);
    glm::mat4 projection = glm::ortho(0.0f, (GLfloat)screenWidth, 0.0f,  (GLfloat)screenHeight, 0.1f, 10.0f);

    {
        glUniformMatrix4fv(viewID, 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(projectionID, 1, GL_FALSE, glm::value_ptr(projection));

        glm::mat4 translate = glm::translate(glm::mat4(1.0), glm::vec3(100.0f + move_x, 100.0f + move_y, 0.0f));
        glm::mat4 rotate = glm::rotate(glm::mat4(1.0), 0.0f, glm::vec3(0.0f, 0.0f, 1.0f));
        glm::mat4 scale = glm::scale(glm::mat4(1.0), glm::vec3(1.0f, 1.0f, 2.0f));

        glm::mat4 model = translate * rotate * scale;
        glUniformMatrix4fv(modelID, 1, GL_FALSE, glm::value_ptr(model));

        glUniform4f(color, 0.0f, 0.0f, 1.0f, 1.0f);

        //Render
        glDrawArrays(GL_TRIANGLE_FAN, 0, 360);
    }

    {
        glUniformMatrix4fv(viewID, 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(projectionID, 1, GL_FALSE, glm::value_ptr(projection));

        glm::mat4 translate = glm::translate(glm::mat4(1.0), glm::vec3(300.0f + injPipette.x, 300.0f + injPipette.y, 0.0f));
        glm::mat4 rotate = glm::rotate(glm::mat4(1.0), 0.0f, glm::vec3(0.0f, 0.0f, 1.0f));
        glm::mat4 scale = glm::scale(glm::mat4(1.0), glm::vec3(1.0f, 1.0f, 2.0f));

        glm::mat4 model = translate * rotate * scale;
        glUniformMatrix4fv(modelID, 1, GL_FALSE, glm::value_ptr(model));

        glUniform4f(color, 1.0f, 0.0f, 0.0f, 0.5f);

        //Render
        glDrawArrays(GL_TRIANGLES, 0, 6);
    }

我重复，使用我已经完成过的相同顶点绘制多个对象。我需要知道如何使用相同的顶点和片段着色器但顶点数量不同来绘制多个对象。该项目很小，仅能以2D渲染最多10个对象。

Answer 1

[类似于glDrawArrays的绘制命令处理并绘制通用顶点属性数据的数组，这些数组在当前的glDrawArrays中说明。

这意味着您必须在进行绘制调用之前绑定适当的顶点数组对象：

Vertex Array Object