Question

我一直致力于从OpenGL获取屏幕截图，然后在屏幕上呈现相同的屏幕截图。为此，我创建了两个帧缓冲区。 1用于渲染（ratinaFramebuffer）和1用于使用apple纹理缓存绘图（textureFramebuffer）。使用以下代码创建两者（变量名称除外）。

glGenFramebuffers(1, &ratinaFramebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, ratinaFramebuffer);

glGenRenderbuffers(1, &ratinaColorRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, ratinaColorRenderbuffer);
[_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:_eaglLayer];

glGenRenderbuffers(1, &ratinaDepthRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, ratinaDepthRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, ratinaDepthRenderbuffer);

GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER) ;
if(status != GL_FRAMEBUFFER_COMPLETE)
{
    NSLog(@"failed to make complete framebuffer object %x", status);
}

这是我的渲染代码的样子

glBindTexture(GL_TEXTURE_2D, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);

// Clear content
glBindFramebuffer(GL_FRAMEBUFFER, ratinaFramebuffer);
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

glBindFramebuffer(GL_FRAMEBUFFER, textureFramebuffer);
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Start drawing
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);

static int nColor = 104;


glClearColor(0, (++nColor & 0xff)/255.0, 55.0/255.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);

CC3GLMatrix *projection = [CC3GLMatrix matrix];
float h = 4.0f * self.frame.size.height / self.frame.size.width;
[projection populateFromFrustumLeft:-2 andRight:2 andBottom:-h/2 andTop:h/2 andNear:4 andFar:10];
glUniformMatrix4fv(_projectionUniform, 1, 0, projection.glMatrix);

CC3GLMatrix *modelView = [CC3GLMatrix matrix];
[modelView populateFromTranslation:CC3VectorMake(sin(CACurrentMediaTime()), 0, -7)];
_currentRotation += displayLink.duration * 90;
[modelView rotateBy:CC3VectorMake(_currentRotation, _currentRotation, 0)];
glUniformMatrix4fv(_modelViewUniform, 1, 0, modelView.glMatrix);

// 1
glViewport(0, 0, self.frame.size.width, self.frame.size.height);

glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);

// 2
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));

glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _floorTexture);
glUniform1i(_textureUniform, 0);

// 3
glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);

glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer2);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer2);

glActiveTexture(GL_TEXTURE0); // unneccc in practice
glBindTexture(GL_TEXTURE_2D, _fishTexture);
glUniform1i(_textureUniform, 0); // unnecc in practice

glUniformMatrix4fv(_modelViewUniform, 1, 0, modelView.glMatrix);

glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));
glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));

glDrawElements(GL_TRIANGLE_STRIP, sizeof(Indices2)/sizeof(Indices2[0]), GL_UNSIGNED_BYTE, 0);


// Get the image
CGImageRef cgImage = NULL;
UIImage *screenImageimage = nil;
OSStatus res = CreateCGImageFromCVPixelBuffer(renderTarget,&cgImage);
if (res == noErr)
{
    screenImageimage = [UIImage imageWithCGImage:cgImage scale:1.0 orientation:UIImageOrientationUp];

}

此时，图像被完美地绘制到纹理中。但是当我尝试在屏幕上渲染它时，相同的纹理，它不会被绘制:(。它显示了我用清晰的颜色给出的蓝色，但没有别的。

glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ratinaFramebuffer);
glBindTexture(GL_TEXTURE_2D, 0);
glClearColor(0, 255/255.0, 255/255.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);

glViewport(0, 0, self.frame.size.width, self.frame.size.height);


glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, renderTexture);


// Display the buffer
glBindRenderbufferOES(GL_RENDERBUFFER_OES, ratinaColorRenderbuffer);
[_context presentRenderbuffer:GL_RENDERBUFFER_OES];

Answer 1

当你绘制到单独的帧缓冲区时，你可以附加一个纹理，最后你可以有效地绘制到纹理本身。完成此绘图后，您可以像使用任何其他绘图一样使用纹理，包括将其绘制到主屏幕缓冲区。

这样做时应该检查几点：

切换
切换时必须根据绑定的帧缓冲区设置视口
可能您可能需要清除缓冲区
可能仅在缓冲区的一部分上绘制纹理，例如在1024x1024纹理上绘制600x600屏幕。在这种情况下，您需要生成范围[0,600 / 1024]中的顶点坐标以绘制它的正确部分。这可以通过比较纹理绑定帧缓冲区的视口值和纹理大小来检查。

很难说你现在缺少什么，但目前最好的镜头是检查视口。除此之外，如果您只是绘制全屏纹理，则无需使用主缓冲区复杂化。您可以禁用矩阵，只需使用默认的[-1,1]坐标系。

Answer 2

问题解决了，因为我是openGL的新手并且我没有绘制屏幕帧缓冲，我通过在屏幕调用的渲染中使用下面的代码来完成。如果有人需要在初级阶段查看，那就发布了

GLfloat     coordinates[] = { 0,    1,
                              1,    1,
                              0,    0,
                              1,    0 };

GLfloat     width = self.frame.size.width,
            height =  self.frame.size.height;

GLfloat     vertices[] = {  -width / 2 + point.x,   -height / 2 + point.y,  0.0,
                            width / 2 + point.x,    -height / 2 + point.y,  0.0,
                            -width / 2 + point.x,   height / 2 + point.y,   0.0,
                            width / 2 + point.x,    height / 2 + point.y,   0.0 };

glBindTexture(GL_TEXTURE_2D, CVOpenGLESTextureGetName(renderTexture));

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

glVertexPointer(3, GL_FLOAT, 0, vertices);
glTexCoordPointer(2, GL_FLOAT, 0, coordinates);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

虽然，这显示了纹理但是在另一个帧缓冲区中绘制的小盒子中。虽然顶点和坐标是完整的屏幕，但它不会绘制到完整的屏幕。如果我找到了，就会编辑这个。

纹理缓存不会渲染到iOS中的帧缓冲区对象中

2 个答案: