我正在使用 OpenGL 制作一个程序，该程序在 GPU 中渲染帧，然后将其传输到内存，以便我可以在另一个程序中使用它们。我不需要窗口或渲染到屏幕，因此我使用 GLFW，但带有隐藏的窗口和上下文。在 opengl-tutorial.com 之后，我设置了一个带有纹理和深度渲染缓冲区的帧缓冲区，这样我就可以渲染到纹理，然后读取它的像素。只是为了检查我可以使窗口可见，并且我正在四边形上将纹理渲染回屏幕上并使用直通着色器。
我的问题是，当我直接渲染到屏幕(没有帧缓冲区或纹理)时，图像看起来很棒且平滑。但是，当我渲染到纹理然后将纹理渲染到屏幕时，它看起来呈锯齿状。我认为问题不在于将纹理渲染到屏幕上，因为我还将读取的像素保存到 .jpg 中，并且那里看起来也有锯齿状。
窗口和纹理的大小均为 512x512 像素。
这是我设置帧缓冲区的代码:
FramebufferName = 0;
glGenFramebuffers(1, &FramebufferName);
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
//GLuint renderedTexture;
glGenTextures(1, &renderedTexture);
glBindTexture(GL_TEXTURE_2D, renderedTexture);
glTexImage2D(GL_TEXTURE_2D, 0, textureFormat, textureWidth, textureHeight, 0, textureFormat, GL_UNSIGNED_BYTE, 0);
numBytes = textureWidth * textureHeight * 3; // RGB
pixels = new unsigned char[numBytes]; // allocate image data into RAM
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//GLuint depthrenderbuffer;
glGenRenderbuffers(1, &depthrenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, textureWidth, textureHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);
DrawBuffers[0] = GL_COLOR_ATTACHMENT0;
glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
std::cout << "Couldn't set up frame buffer" << std::endl;
}
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(-1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(1.0f);
g_quad_vertex_buffer_data.push_back(0.0f);
//GLuint quad_vertexbuffer;
glGenBuffers(1, &quad_vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, g_quad_vertex_buffer_data.size() * sizeof(GLfloat), &g_quad_vertex_buffer_data[0], GL_STATIC_DRAW);
// PBOs
glGenBuffers(cantPBOs, pboIds);
for(int i = 0; i < cantPBOs; ++i) {
glBindBuffer(GL_PIXEL_PACK_BUFFER, pboIds[i]);
glBufferData(GL_PIXEL_PACK_BUFFER, numBytes, 0, GL_DYNAMIC_READ);
}
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
index = 0;
nextIndex = 0;
这是我渲染纹理的代码:
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
glViewport(0,0,textureWidth,textureHeight); // Render on the whole framebuffer, complete from the lower left corner to the upper right
// Clear the screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
for(int i = 0; i < geometriesToDraw.size(); ++i) {
geometriesToDraw[i]->draw(program);
}
其中draw(ShaderProgram)是调用glDrawArrays的函数。这是我将纹理渲染到屏幕的代码:
// Render to the screen
glBindFramebuffer(GL_FRAMEBUFFER, 0);
// Render on the whole framebuffer, complete from the lower left corner to the upper right
glViewport(0,0,textureWidth,textureHeight);
// Clear the screen
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(shaderTexToScreen.getProgramID());
// Bind our texture in Texture Unit 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, renderedTexture);
// Set our "renderedTexture" sampler to user Texture Unit 0
glUniform1i(shaderTexToScreen.getUniformLocation("renderedTexture"), 0);
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
glVertexAttribPointer(
0,
3,
GL_FLOAT,
GL_FALSE,
0,
(void*)0
);
glDrawArrays(GL_TRIANGLES, 0, 6);
glDisableVertexAttribArray(0);
这是我直接将场景渲染到屏幕时得到的结果:
这就是我将场景渲染到纹理时得到的结果:
我可以包含用于将纹理渲染到屏幕的顶点和片段着色器的代码，但当我直接从纹理读取像素数据并将其写入文件时，它看起来仍然是锯齿状的，我不这样做认为这就是问题所在。如果您希望我添加任何其他内容，请告诉我!
我想可能是在渲染纹理时存在一些隐藏的缩放，所以 GL_NEAREST 使它看起来很糟糕，但如果它确实是像素到像素(窗口和纹理大小相同)，那么应该'那里不会有问题吧？
最佳答案
正如 genpfault 和 Frischer Hering 所指出的，渲染到普通纹理时没有抗锯齿功能。但是，您可以渲染为多重采样纹理，它将保存您请求的尽可能多的样本的信息。要将其渲染到屏幕上，您需要对纹理进行采样以获得每个像素的一种颜色，这可以通过调用 glBlitFramebuffer 来完成。根据glBlitFramebuffer的OpenGL引用:
If SAMPLE_BUFFERS for the read framebuffer is greater than zero and SAMPLE_BUFFERS for the draw framebuffer is zero, the samples corresponding to each pixel location in the source are converted to a single sample before being written to the destination.
这两个链接也非常有帮助:
http://www.learnopengl.com/#!Advanced-OpenGL/Anti-aliasing http://ake.in.th/2013/04/02/offscreening-and-multisampling-with-opengl/
这是我的解决方案，创建对象:
/// FRAMEBUFFER MULTISAMPLE
framebufferMS = 0;
glGenFramebuffers(1, &framebufferMS);
glBindFramebuffer(GL_FRAMEBUFFER, framebufferMS);
glGenTextures(1, &renderedTextureMS);
glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, renderedTextureMS);
glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, SAMPLES, textureFormat, textureWidth, textureHeight, GL_TRUE);
glGenRenderbuffers(1, &depthrenderbufferMS);
glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbufferMS);
glRenderbufferStorageMultisample(GL_RENDERBUFFER, SAMPLES, GL_DEPTH24_STENCIL8, textureWidth, textureHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbufferMS);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTextureMS, 0);
DrawBuffersMS[0] = GL_COLOR_ATTACHMENT0;
glDrawBuffers(1, DrawBuffersMS);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
std::cout << "Couldn't set up frame buffer" << std::endl;
}
/// FRAMEBUFFER SIMPLE
framebuffer = 0;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glGenTextures(1, &renderedTexture);
glBindTexture(GL_TEXTURE_2D, renderedTexture);
glTexImage2D(GL_TEXTURE_2D, 0, textureFormat, textureWidth, textureHeight, 0, textureFormat, GL_UNSIGNED_BYTE, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);
DrawBuffers[0] = GL_COLOR_ATTACHMENT0;
glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
std::cout << "Couldn't set up frame buffer" << std::endl;
}
以及渲染过程:
// Render to framebuffer multisample
glBindFramebuffer(GL_FRAMEBUFFER, framebufferMS);
glViewport(0,0,textureWidth,textureHeight);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
for(int i = 0; i < geometriesToDraw.size(); ++i) {
geometriesToDraw[i]->draw(program);
}
// Sample to normal texture
glBindFramebuffer(GL_READ_FRAMEBUFFER, framebufferMS);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, framebuffer);
glBlitFramebuffer(0, 0, textureWidth, textureHeight, 0, 0, textureWidth, textureHeight, GL_COLOR_BUFFER_BIT, GL_NEAREST);
您还可以在 stackoverflow 上找到有关该主题的更多问题，我错过了这些问题，因为我搜索的是“锯齿状”等术语，而不是多重采样:P
非常感谢您的帮助!
关于c++ - OpenGL 渲染到纹理看起来呈锯齿状，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40405614/