Renderbuffers大于窗口大小-OpenGL

我正在尝试绘制一个大于屏幕大小（即320x480）的渲染缓冲区（512x512）

在执行glReadPixels后，图像看起来是正确的，除非图像的尺寸超过屏幕尺寸-在本例中，超过320水平和480垂直。是什么导致这种异常？有什么我遗漏的吗？ 当窗口大小>=renderbuffer的大小时，此代码工作得非常好

渲染到缓冲区的示例图像&glReadPixel'd:

答案是这样的

更改此行： bglBindFramebuffer（BGL_RENDERBUFFER，canvasFrameBuffer）

为此：

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bglBindFramebuffer（BGL_FRAMEBUFFER，canvasFrameBuffer）

有一个默认为窗口大小的剪切矩形。可能有一种方法可以改变它。参见这里的第10.040项：BGL的废话是什么？此外，这是关于OpenGL还是OpenGL ES的？bgl只是一个包装器，可以帮助避免不同类型驱动程序的EXT/ARB问题。这是桌面GL和GLE，但使用GLE子集。我想它可能也被剪掉了，但我已经把格洛托调好了。原来我在glBindFramebuffer上使用了GL_RENDERBUFFER而不是GL_FRAMEBUFFER。多简单啊P

unsigned int canvasFrameBuffer;
bglGenFramebuffers(1, &canvasFrameBuffer);
bglBindFramebuffer(BGL_RENDERBUFFER, canvasFrameBuffer);

// Attach renderbuffer
unsigned int canvasRenderBuffer;
bglGenRenderbuffers(1, &canvasRenderBuffer);
bglBindRenderbuffer(BGL_RENDERBUFFER, canvasRenderBuffer);
bglRenderbufferStorage(BGL_RENDERBUFFER, BGL_RGBA4, width, height);
bglFramebufferRenderbuffer(BGL_FRAMEBUFFER, BGL_COLOR_ATTACHMENT0, BGL_RENDERBUFFER, canvasRenderBuffer);

bglViewport(0, 0, width, height);

Matrix::matrix_t identity, colorMatrix;
Matrix::LoadIdentity(&identity);
Matrix::LoadIdentity(&colorMatrix);
bglClearColor(1.0f, 1.0f, 1.0f, 1.0f);
bglClear(BGL_COLOR_BUFFER_BIT);

Vector::vector_t oldPos, oldScale;
Vector::Copy(&oldPos, &pos);
Vector::Mul(&pos, 0.0f);
Vector::Copy(&oldScale, &scale);
Vector::Load(&scale, 1, 1, 1);
int oldHAlign = halignment;
int oldVAlign = valignment;
halignment = Font::HALIGN_LEFT;
valignment = Font::VALIGN_BOTTOM;
float oldXRatio = vid.xratio;
float oldYRatio = vid.yratio;
vid.xratio = 1;
vid.yratio = 1;
Drawing::Set2D(this->size.x, this->size.y); // glOrtho and setup projection/modelview matrices
Draw(&identity, &colorMatrix);
Vector::Copy(&pos, &oldPos);
Vector::Copy(&scale, &oldScale);
halignment = oldHAlign;
valignment = oldVAlign;
vid.xratio = oldXRatio;
vid.yratio = oldYRatio;

byte *buffer = (byte*)Z_Malloc(width * height * 3, ZT_STATIC);
bglPixelStorei(BGL_PACK_ALIGNMENT, 1);
bglReadPixels(0, 0, width, height, BGL_RGB, BGL_UNSIGNED_BYTE, buffer);

byte *final = RGBtoLuminance(buffer, width, height);

SaveTGA("canvas.tga", final, width, height, 1);

Z_Free(buffer);

// unbind frame buffer
bglBindRenderbuffer(BGL_RENDERBUFFER, 0);
bglBindFramebuffer(BGL_FRAMEBUFFER, 0);
bglDeleteRenderbuffers(1, &canvasRenderBuffer);
bglDeleteFramebuffers(1, &canvasFrameBuffer);

bglViewport(0, 0, vid.width, vid.height);