如何在OpenGL Core 3.3中使用正交投影绘制圆?

我对OpenGL编程是一个完全的初学者,我正在努力学习 learnopengl.com 但是我想把球画成一个实际的圆,而不是像乔伊建议的那样使用有纹理的四边形。然而,谷歌因为“DrawCircle opengl 3.3”或类似短语而向我抛出的每一个结果似乎都至少有几年的历史了,而且使用的API版本甚至比那个版本还要旧:-(

我找到的最接近的东西是 this SO question 当然,行动只是 使用自定义 VertexFormat 对象抽象了一些细节,没有分享他/她这样的实现!只是我的运气!:页

还有 this YouTube tutorial 它使用了一个看似较旧的API版本,但是逐字复制代码(除了最后几行代码看起来很旧)仍然让我一无所获。

我的版本 SpriteRenderer::initRenderData()

void SpriteRenderer::initRenderData() {
    GLuint vbo;

    auto attribSize = 0;
    GLfloat* vertices = nullptr;

    // Determine whether this sprite is a circle or
    // quad and setup the vertices array accordingly
    if (!this->isCircle) {
        attribSize = 4;
        vertices = new GLfloat[24] {...}   // works for rendering quads
    } else {
        // This code is adapted from the YouTube tutorial that I linked
        // above and is where things go pear-shaped for me...or at least
        // **not** circle-shaped :P
        attribSize = 3;

        GLfloat x = 0.0f;
        GLfloat y = 0.0f;
        GLfloat z = 0.0f;
        GLfloat r = 100.0f;

        GLint numSides = 6;
        GLint numVertices = numSides + 2;

        GLfloat* xCoords = new GLfloat[numVertices];
        GLfloat* yCoords = new GLfloat[numVertices];
        GLfloat* zCoords = new GLfloat[numVertices];

        xCoords[0] = x;
        yCoords[0] = y;
        zCoords[0] = z;

        for (auto i = 1; i < numVertices; i++) {
            xCoords[i] = x + (r * cos(i * (M_PI * 2.0f) / numSides));
            yCoords[i] = y + (r * sin(i * (M_PI * 2.0f) / numSides));
            zCoords[i] = z;
        }

        vertices = new GLfloat[numVertices * 3];
        for (auto i = 0; i < numVertices; i++) {
            vertices[i * 3] = xCoords[i];
            vertices[i * 3 + 1] = yCoords[i];
            vertices[i * 3 + 2] = zCoords[i];
        }
    }

    // This is where I go back to the learnopengl.com code. Once
    // again, the following works for quads but not circles!
    glGenVertexArrays(1, &vao);
    glGenBuffers(1, &vbo);

    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, 24 * sizeof(
        GLfloat), vertices, GL_STATIC_DRAW);

    glBindVertexArray(vao);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(0, attribSize, GL_FLOAT, GL_FALSE,
        attribSize * sizeof(GLfloat), (GLvoid*)0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

下面是 SpriteRenderer::DrawSprite() 方法(与原始方法的唯一区别是第24-28行):

void SpriteRenderer::Draw(vec2 position, vec2 size, GLfloat rotation, vec3 colour) {
    // Prepare transformations
    shader.Use();

    auto model = mat4(1.0f);
    model = translate(model, vec3(position, 0.0f));

    model = translate(model, vec3(0.5f * size.x, 0.5f * size.y, 0.0f));   // Move origin of rotation to center
    model = rotate(model, rotation, vec3(0.0f, 0.0f, 1.0f));              // Rotate quad
    model = translate(model, vec3(-0.5f * size.x, -0.5f * size.y, 0.0f)); // Move origin back

    model = scale(model, vec3(size, 1.0f)); // Lastly, scale

    shader.SetMatrix4("model", model);

    // Render textured quad
    shader.SetVector3f("spriteColour", colour);

    glActiveTexture(GL_TEXTURE0);
    texture.Bind();

    glBindVertexArray(vao);

    if (!isCircular) {
        glDrawArrays(GL_TRIANGLES, 0, 6);
    } else {
        glDrawArrays(GL_TRIANGLE_FAN, 0, 24);  // also tried "12" and "8" for the last param, to no avail
    }

    glBindVertexArray(0);
}

最后,着色器(与用于四边形的着色器不同):

// Vertex shader
#version 330 core

layout (location = 0) in vec3 position;

uniform mat4 model;
uniform mat4 projection;

void main() {
    gl_Position = projection * model *
        vec4(position.xyz, 1.0f);
}

// Fragment shader
#version 330 core

out vec4 colour;

uniform vec3 spriteColour;

void main() {    
    colour = vec4(spriteColour, 1.0);
}

全部的

P、 我刚意识到learnopengl.com网站这个网站有一个专门调试OpenGL应用程序的部分,所以我设置了这个部分,但是没有用:-(我认为我的驱动程序(inteluhdgraphics620最新的驱动程序)不支持错误处理,因为 GL_CONTEXT_FLAG_DEBUG_BIT 未按照说明进行设置:

在GLFW中请求一个调试上下文非常容易,因为我们所要做的就是向GLFW传递一个提示,表示我们想要一个调试输出上下文。在调用glfwCreateWindow之前,我们必须这样做:

glfwWindowHint(GLFW\u OPENGL\u DEBUG\u CONTEXT,GL\u TRUE);

一旦我们初始化GLFW,如果我们使用的是opengl4.3或更高版本,我们就应该有一个调试上下文,否则我们就必须冒险,希望系统仍然能够请求一个调试上下文。否则,我们必须使用OpenGL扩展请求调试输出。

要检查是否成功初始化调试上下文,可以查询OpenGL:

GLint flags;glGetIntegerv(GL\u CONTEXT\u flags,&flags);

if(标志和GL\u上下文\u标志\u调试\u位){

if 声明永远不会被输入!