c++ - 渲染到帧缓冲区/纹理显示为空

Question

我正在尝试渲染到帧缓冲区(与窗口/屏幕大小相同)以进行后期处理。一切都是二维的，所以应该不会有太大的麻烦。直接渲染到屏幕上效果很好。但我只得到清晰的颜色和一个空的缓冲区。将任何内容渲染到其中的唯一方法是在位置 (0,0) 处渲染一个与缓冲区大小完全相同的矩形，这很奇怪。

我尝试将随机位置渲染到缓冲区中，但没有任何效果。将缓冲区显示/渲染到屏幕有效。

这是我创建缓冲区的方式:

    glGenFramebuffers(1, &fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
    std::cout << "frame buffer fbo: " << fbo << std::endl;

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
        std::cout << "error creating screen buffer width: " << width << " height: " << height << std::endl;
    }
    else {
        std::cout << "created screen buffer width: " << width << " height: " << height << std::endl;
    }

    glBindFramebuffer(GL_FRAMEBUFFER, 0);

顶点着色器:

#version 330 core

layout (location = 0) in vec2 vertex;
uniform mat4 projection;

void main() {
    gl_Position = projection * vec4(vertex.x, vertex.y, 0.0f, 1.0f);
}

片段着色器:

#version 330 core

uniform vec4 in_color;
out vec4 FragColor ;

void main() {
    FragColor = in_color;
}

渲染投影矩阵:

glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(this->width), static_cast<GLfloat>(this->height), 0.0f, -1.0f, 1.0f);

渲染到缓冲区的代码:

// binding and clearing the buffer to render into it
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glViewport(0, 0, width, height);
glClearColor(0.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);

// render the rectangle
renderer->drawRectangle(0, 0, 10, 10, glm::vec4(1.0f, 0.0f, 1.0f, 1.0f));

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glViewport(0, 0, resolutionWidth, resolutionHeight);

// rendering main screen showing the quad

结果是这样的(以一半大小呈现到屏幕的缓冲区): Empty Quad/framebuffer showing clear color

Answer 1

我在实现这个时遵循了本教程:https://learnopengl.com/Advanced-OpenGL/Framebuffers

作为我的解决方案，我只是更改了屏幕着色器以接受我的顶点/纹理数据。然后我注意到实际的缓冲区数据非常好......

顶点着色器:

#version 330 core
layout (location = 0) in vec4 aPos;

out vec2 TexCoords;

void main()
{
    TexCoords = aPos.zw;
    gl_Position = vec4(aPos.x, aPos.y, 0.0, 1.0);
} 

片段着色器:

#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D screenTexture;

void main()
{ 
    FragColor = texture(screenTexture, TexCoords);
}