实现渲染到顶点数组，glReadPixels 失败（无效操作）
我正在尝试将顶点数据从纹理复制到顶点缓冲区，然后绘制顶点缓冲区。据我所知，最好的方法是将纹理绑定到 fbo，并使用 glReadPixels 将其复制到 vbo。但是，我似乎无法正常工作：glReadPixels 失败并出现错误“无效操作”。
欢迎更正、示例和替代方法。 :)
这是相关代码：
glEnable(GL_TEXTURE_2D)
w, h = 32, 32
vbo = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, sizeof(c_float)*w*h*4, None, GL_STREAM_COPY)
glBindBuffer(GL_ARRAY_BUFFER, 0)
fbo = glGenFramebuffersEXT(1)
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo)
tex = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, tex)
# tex params here
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, w, h, 0, GL_RGBA, GL_FLOAT, None)
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0)
assert glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) == 36053
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT)
glBindBuffer(GL_PIXEL_PACK_BUFFER, vbo)
glReadPixels(0, 0, w, h, GL_RGBA, GL_FLOAT, None) # invalid operation?
I'm trying to copy vertex data from a texture to a vertex buffer, and then draw the vertex buffer. As far as I know the best way to do this is to bind the texture to a fbo, and use glReadPixels to copy it to a vbo. However, I can't seem to get this working: glReadPixels fails with the error "invalid operation".
Corrections, examples and alternate methods welcome. :)
Here's the relevant code:
glEnable(GL_TEXTURE_2D)
w, h = 32, 32
vbo = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, sizeof(c_float)*w*h*4, None, GL_STREAM_COPY)
glBindBuffer(GL_ARRAY_BUFFER, 0)
fbo = glGenFramebuffersEXT(1)
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo)
tex = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, tex)
# tex params here
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, w, h, 0, GL_RGBA, GL_FLOAT, None)
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, tex, 0)
assert glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) == 36053
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT)
glBindBuffer(GL_PIXEL_PACK_BUFFER, vbo)
glReadPixels(0, 0, w, h, GL_RGBA, GL_FLOAT, None) # invalid operation?
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我自己已经解决了这个问题。
在这种情况下，ReadPixels 的最后一个参数用作偏移量而不是指针，并且不会由 pyopengl 自动转换，请使用：
I've solved the issue myself.
The last argument to ReadPixels is used as an offset instead of a pointer in this case, and is not automatically cast by pyopengl, use: