[英]OpenGL Offscreen Rendering Returning Clear Color
我有一个简单的函数,该函数应该接收OpenGL中存在的现有纹理并将其调整大小/缩小到给定的宽度和高度,并返回新纹理ID的ID。
第一次,它运行良好,代码可以在相同的源纹理甚至结果纹理上多次运行(循环)。 但是,一旦帧通过,该代码将不再起作用。 一旦函数损坏,结果将是具有正确宽度和高度输入的纹理,但是它根本不使用输入纹理,并且输出像素是使用glClearColor(0, 1, 1, 1);
像素glClearColor(0, 1, 1, 1);
。 使用旧版OpenGL代码显示彩色四边形也可以运行一次,然后停止工作,这提示我问题不在于输入纹理,而几何图形未在FBO中绘制。
GLuint Texture::Downsample(int width, int height, GLuint source)
{
// Use the largest values
width = Max(16, width);
height = Max(16, height);
// Create a frame buffer object
GLuint fbo, rbo, target_texture;
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glGenTextures(1, &target_texture); // Create the target texture
GLenum status;
// : Target Texture :
glBindTexture(GL_TEXTURE_2D, target_texture); // Bind the texture position unit to be used as a buffer
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(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);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_SHORT, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, target_texture, 0); // Setup the Framebuffer
status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE) throw;
glGenRenderbuffers(1, &rbo);
glBindRenderbuffer(GL_RENDERBUFFER, rbo);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, rbo);
status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE) throw;
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
// Use the FBO to draw to the color attachment
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
glDrawBuffer(GL_COLOR_ATTACHMENT0);
glPushAttrib(GL_VIEWPORT_BIT | GL_COLOR_BUFFER_BIT);
glViewport(0, 0, width, height);
glClearColor(0, 1, 1, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDisable(GL_DEPTH_TEST);
// : Draw the original texture
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
//this->Bind(GL_TEXTURE0);
glEnable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, source);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glDisable(GL_DEPTH_TEST); // Disable Depth Testing
glDisable(GL_CULL_FACE);
// Geometry Data
const float uvdata[] = { 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f };
const float geometrydata[] = { -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, 1.0f, 1.0f, 0.0f, -1.0f, 1.0f, 0.0f };
const unsigned char indices[] = { 0, 1, 2, 2, 3, 0 };
glEnableClientState(GL_VERTEX_ARRAY); // Enable Client Vertex Arrays
glEnableClientState(GL_TEXTURE_COORD_ARRAY); // Enable Client Texture Coordinate Arrays
glVertexPointer(3, GL_FLOAT, 0, &geometrydata[0]); // Pass the geometry data into the Vertex Array
glTexCoordPointer(2, GL_FLOAT, 0, &uvdata[0]); // Pass the UV data into the Texture Coordinate Array
// Draw the geometry using the indices
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices);
glDisableClientState(GL_TEXTURE_COORD_ARRAY); // Disable Client Texture Coordinate Arrays
glDisableClientState(GL_VERTEX_ARRAY); // Disable Client Vertex Arrays
glPopAttrib();
glDeleteTextures(1, &source); // Delete the old texture
glDrawBuffer(GL_NONE);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glDeleteFramebuffers(1, &fbo);
glDeleteRenderbuffers(1, &rbo);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, target_texture);
int w, h;
int miplevel = 0;
glGetTexLevelParameteriv(GL_TEXTURE_2D, miplevel, GL_TEXTURE_WIDTH, &w);
glGetTexLevelParameteriv(GL_TEXTURE_2D, miplevel, GL_TEXTURE_HEIGHT, &h);
return target_texture;
}
找到了答案(按照我提出问题的10分钟的常规方法)。 我正在运行OpenGL的多上下文实现。 因此,在函数返回后立即使用了输入的纹理ID,但是GPU尚未完成处理。
只需在返回之前添加glFinish()
并创建互斥锁方案就可以了。 然后,当访问纹理时,将在互斥锁上尝试锁,以确定是否正在使用该纹理。
例如。 Mutex.Instance.lock(); TextureID_Internal = Downsample(128,128, TextureID_Internal); Mutex.Instance.unlock();
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