On 13.04.2017 18:39, gregory hainaut wrote:
On Thu, 13 Apr 2017 18:31:06 +0200
Nicolai Hähnle <nhaeh...@gmail.com> wrote:
On 05.04.2017 12:30, Gregory Hainaut wrote:
# Classify fixed and variable parameters.
self.fixed_params = []
self.variable_params = []
for p in self.parameters:
if p.is_padding:
continue
- if p.is_variable_length():
+ if self.marshal == "upbo" and p.is_pointer():
+ # Pixel buffer transfer API is tricky. By default
it contains
+ # a pointer to user memory so a variable length parameter.
+ # When a pixel buffer is bound, the pointer
becomes an offset.
+ #
+ # Non-PBO transfer will be synchronous so
parameter type isn't
+ # important. PBO transfer will be asynchronous so
the parameter
+ # must be marked as fixed
+ self.fixed_params.append(p)
If this is needed for upbo, shouldn't it also be needed for ppbo?
Cheers,
Nicolai
Hello Nicolai,
It isn't symmetrical. In case of UPBO data ought to be copied from app
thread to gl thread. You can see variable_length parameter as input
pointer. Variable length will generate the memcpy code.
However PPBO will copy from GPU to user pointer. There is no data
associated with the pointer so the pointer isn't "used" by glthread,
only transferred to GL.
I think the code would love an extra comment.
Okay, I get it now. But the comment could maybe use some re-wording,
especially because this whole issue only applies to some functions:
those where the marshaling code theoretically has a size, such as with
glCompressedTexImage2D. It would be good to clarify that.
Yes. I added this comment. Though I'm not sure it enough.
+ # variable_params are meaningful when pointers are associated
+ # with a payload hence it only impacts upbo but not ppbo.
I'd rewrite the thing. Here's a suggestion:
# There are some texture upload functions (the CompressedTexImage
# family) which provide an imageSize together with the image
# pointer. The default marshaling behavior is to copy the contents
# of image to a variable length section, which is incorrect when
# image refers to a pixel buffer.
#
# This ensures that the pointer is marshaled as is. The non-PBO
# case is always synchronous and so does not use marshaling anyway.
Cheers,
Nicolai
--
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.
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