[squeak-dev] Re: Still pounding head against wall over
glReadPixels => external buffer
lenglish5 at cox.net
Thu Feb 11 15:45:27 UTC 2010
Hi Andreas. Even if I use a normally allocated bit of memory, I can't
get it to work:
xHandle := ExternalAddress allocate: 100 * 100 * 4. "create external
xData := ExternalData fromHandle: xHandle type: ExternalType void
asPointerType. "convert for use with glReadPixels"
ogl := OpenGL newIn: (0 at 0 extent:100 at 100). "create ogl context"
ogl glClearColor(0.2, 0.9, 0.7, 0.5). "set clear color"
ogl glClear(16r4000). "clear backbuffer"
ogl swapBuffers. "draw to screen"
ogl "read pixels into my buffer"
with: ogl imagePixelFormat32
with: ogl imagePixelType32
xHandle byteAt: 1000=> 0 "print byte value in my buffer???"
xHandle byteAt: 1000 put: 10 "manually set byte value in my buffer"
xHandle byteAt: 1000 => 10 "print byte value in my buffer???????"
Andreas Raab wrote:
> Lawson English wrote:
>> I'm still having problems with my external shared memory thingie. I
>> can evoke the unix shm* calls and obtain a reference to a shared
>> memory buffer and attach it to squeak's heap. I can write into it and
>> read back. I can even attach the same shared memory to two different
>> instances of squeak and write to the buffer in one and read it with
>> the other. What I still cannot figure out is how to take that
>> external buffer and direct the OpenGL>>glReadPixels call to it so
>> that I can draw using squeak and have it become a bitmap for a
>> different application.
> Post your code. Using glReadPixels is straightforward, so there must
> be something simple in your code that goes wrong. Simply speaking the
> following should work fine:
> "Allocate or obtain shared memory buffer"
> xHandle := ExternalHandle allocate: rect width * rect height * 4.
> "Convert it to ExternalData"
> xData := ExternalData fromHandle: xHandle type: ExternalType void
> "Call glReadPixels"
> glReadPixels: rect left
> with: ogl extent y - rect bottom
> with: rect width
> with: rect height
> with: ogl imagePixelFormat32
> with: ogl imagePixelType32
> with: xData.
> This should be all there is to it.
> - Andreas
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