GLGETCONVOLUTIONPARAMETER(3G)

💖 GLGETCONVOLUTIONPARAMETER 💖

okay so bestie, this is the glGetConvolutionParameterfv / glGetConvolutionParameteriv page from the 3G manual — it's the one where you peek at your convolution filter's settings instead of setting them. asking, not telling. we love a curious queen 🎀

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✨ C SPECIFICATION ✨

void glGetConvolutionParameterfv( GLenum target,
                                  GLenum pname,
                                  GLfloat *params )
void glGetConvolutionParameteriv( GLenum target,
                                  GLenum pname,
                                  GLint *params )

two flavors, same energy: fv hands you floats, iv hands you ints. pick your fighter 💅

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🌸 PARAMETERS 🌸

• target — the filter whose parameters you're tryna retrieve. has to be one of GL_CONVOLUTION_1D, GL_CONVOLUTION_2D, or GL_SEPARABLE_2D. (three options, no in-between 🦋)
• pname — which parameter you're asking about. must be one of GL_CONVOLUTION_BORDER_MODE, GL_CONVOLUTION_BORDER_COLOR, GL_CONVOLUTION_FILTER_SCALE, GL_CONVOLUTION_FILTER_BIAS, GL_CONVOLUTION_FORMAT, GL_CONVOLUTION_WIDTH, GL_CONVOLUTION_HEIGHT, GL_MAX_CONVOLUTION_WIDTH, or GL_MAX_CONVOLUTION_HEIGHT.
• params — pointer to storage where the retrieved parameters get dropped off. it's giving "leave it at the front desk" 📦

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👑 DESCRIPTION 👑

glGetConvolutionParameter retrieves convolution parameters. target decides which convolution filter gets interrogated. pname decides which parameter comes back out. here's the menu, bestie:

• GL_CONVOLUTION_BORDER_MODE — the convolution border mode. for the full list of border modes, go check glConvolutionParameter. iykyk 💜
• GL_CONVOLUTION_BORDER_COLOR — the current convolution border color. params must be a pointer to an array of four elements, which will receive the red, green, blue, and alpha border colors. four. not three. not five. four 🌈
• GL_CONVOLUTION_FILTER_SCALE — the current filter scale factors. params must be a pointer to an array of four elements, receiving the red, green, blue, and alpha filter scale factors, in that order. order matters, don't come for me ✨
• GL_CONVOLUTION_FILTER_BIAS — the current filter bias factors. params must be a pointer to an array of four elements, receiving the red, green, blue, and alpha filter bias terms, in that order. again: in that order 🫶
• GL_CONVOLUTION_FORMAT — the current internal .

okay yes, that sentence literally just ends there 💀 that's how it is on the original page, so that's how it is here. go peep glConvolutionFilter1D, glConvolutionFilter2D, and glSeparableFilter2D for lists of allowable formats.

• GL_CONVOLUTION_WIDTH — the current filter image width. 📏
• GL_CONVOLUTION_HEIGHT — the current filter image height. 📐
• GL_MAX_CONVOLUTION_WIDTH — the maximum acceptable filter image width. (the ceiling, the limit, the "that's enough" ⭐)
• GL_MAX_CONVOLUTION_HEIGHT — the maximum acceptable filter image height. (same but vertical, slay)

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💀 ERRORS 💀

these are the vibes-ruiners. read them. memorize them. thank me later.

• GL_INVALID_ENUM is generated if target is not one of the allowable values. 🚫
• GL_INVALID_ENUM is generated if pname is not one of the allowable values. 🚫
• GL_INVALID_ENUM is generated if target is GL_CONVOLUTION_1D and pname is GL_CONVOLUTION_HEIGHT or GL_MAX_CONVOLUTION_HEIGHT. 🚫

bestie listen: a 1D filter has no height. asking for its height is not a slay, it's an error. periodt.

• GL_INVALID_OPERATION is generated if glGetConvolutionParameter is executed between the execution of glBegin and the corresponding execution of glEnd. 😭

so basically don't do that inside a glBegin/glEnd block. that's the forbidden window. respect it.

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🦋 SEE ALSO 🦋

• glGetConvolutionFilter(3G)
• glGetSeparableFilter2D(3G)
• glConvolutionParameter(3G)

go read those too, they're the rest of the lore 📚

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and that's the whole page, bestie! this was GLGETCONVOLUTIONPARAMETER(3G) — part of the 3G manual set, dated back in the day and stamped with that same source/version energy at the bottom of the original. now go forth and query your convolution parameters with main character energy 👑✨