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glClearBufferData- How to Use It?


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#1 SHOKWAV   Members   -  Reputation: 129

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Posted 11 December 2012 - 07:24 PM

Hello, I need to learn the proper usage for glClearBufferData for an application I'm creating. I've looked at the official documentation... which isn't very descriptive, mainly what I don't understand are the internalformat, format, and type parameters.

void glClearBufferData( GLenum target,
GLenum internalformat,
GLenum format,
GLenum type,
const void * data);

I have a buffer with a target and some data, and all the data are in float form. I want to clear it all out to 0. Question is, how? Which one do I specify that it's in floats? Internalformat? What about the format and type? I just want to clear out all the memory. I know to specify NULL for data... but what about format and type?

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#2 santa01   Members   -  Reputation: 307

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Posted 13 December 2012 - 11:57 AM

You can look through the http://www.opengl.or...ffer_object.txt document, they got some explanation there:

	To fill all or part of an existing buffer object's data store with a
	constant value, call
		void ClearBufferSubData(enum target,
								enum internalformat,
								enum format,
								enum type,
								sizeiptr offset,
								sizeiptr size,
								const void * data);
	with <target> set to the target to which the destination buffer is bound.
	<target> must be one of the targets listed in Table 2.8.
	<internalformat> must be set to one of the format tokens listed in Table
	3.15, "Internal formats for buffer textures". <format> and <type> specify
	the format and type of the source data and are interpreted as described in
	Section 3.7.2. <offset> set to the offset, measured in basic
	machine units, into the buffer object's data store from which to begin
	filling, and <size> set to the size, also in basic machine units, of the
	range to fill. Both <offset> and <range> must be multiples of the number
	of basic machine units per-element for that internal format specified by
	<internalformat>, otherwise the error INVALID_VALUE is generated.
	<data> is a pointer to an array of between one and four components
	containing the data to be used as the source of the constant fill value.
	The elements of <data> are converted by the GL into the format specified by
	<internalformat> in the manner described in section 2.3.1, and then used to
	fill the specified range of the destination buffer. If <data> is NULL, then
	the pointer is ignored and the sub-range of the buffer is filled with zeros.
	If <offset> or <size> is less than zero, or if <offset> + <size> is
	greater than the value of BUFFER_SIZE for the buffer bound to <target>
	then the error INVALID_VALUE is generated. The command
	An INVALID_OPERATION error is generated if any part of the specified
	range of the buffer bound to <target> is currently mapped.
		void ClearBufferData(enum target,
							 enum internalformat,
							 enum format,
							 enum type,
							 const void * data);
	is equivalent to calling ClearBufferSubData with <target>,
	<internalformat> and <data> as specified, with <offset> set to zero,
	and <size> set to the value of BUFFER_SIZE for the buffer bound to
	<target>.





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