TEXTUREGATHEROFFSET(3G)

💖 TEXTUREGATHEROFFSET 💖

okay bestie, we're doing textureGatherOffset from the 3G manual section today and honestly? it's giving glow-up energy. sit down, hydrate, let's go 🫶

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✨ NAME ✨

textureGatherOffset — gathers four texels from a texture with offset

like... four texels. at once. with an offset. slay 💅

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🌸 DECLARATION 🌸

here's the whole lineup, copy-paste it exactly bestie, don't you dare paraphrase:

gvec4 textureGatherOffset(gsampler2D sampler, vec2 P, ivec2 offset,
                          [int comp]);

gvec4 textureGatherOffset(gsampler2DArray sampler, vec3 P, ivec2 offset,
                          [int comp]);

gvec4 textureGatherOffset(gsampler2DRect sampler, vec3 P, ivec2 offset,
                          [int comp]);

vec4 textureGatherOffset(gsampler2DShadow sampler, vec2 P, float refZ,
                         ivec2 offset);

vec4 textureGatherOffset(gsampler2DArrayShadow sampler, vec3 P,
                         float refZ, ivec2 offset);

vec4 textureGatherOffset(gsampler2DRectShadow sampler, vec3 P,
                         float refZ, ivec2 offset);

notice how the shadow ones get a float refZ instead of an [int comp]? that's not a typo, that's ✨by design✨

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🎀 PARAMETERS 🎀

• sampler — the sampler you've bound the texture to, aka the one you're pulling texels out of. your texture's home address 🏠
• P — the texture coordinates where the sampling happens. where the vibe check occurs 📍
• comp — which component of the source texture gets used to build the resulting vector. you're picking a lane 🛣️
• refZ — the reference Z value used in the comparison, but only for the shadow forms. shadow girls only 🖤
• offset — how far off from that texture coordinate P you're gathering the texels from. the little nudge 👉✨

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💜 DESCRIPTION 💜

so here's literally what textureGatherOffset returns, verbatim:

vec4(Sample_i0_j1(P + offset, base).comp,
     Sample_i1_j1(P + offset, base).comp,
     Sample_i1_j0(P + offset, base).comp,
     Sample_i0_j1(P + offset, base).comp);

(yes, Sample_i0_j1 really does show up twice in there. we don't ask questions, we just gather 🫠)

it perfoms just like textureGather(), except with offset applied exactly as described in textureOffset() — with one little twist: the minimum and maximum offset values are implementation-dependent, and they come from GL_MIN_PROGRRAM_TEXTURE_GATHER_OFFSET and GL_MAX_PROGRAM_TEXTURE_GATHER_OFFSET, respectively. (spelling of that first one is not on me, I'm reporting the facts, periodt.)

if you do specify comp, its value must ba constant integer expression with a value of 0, 1, 2, or 3, identifying the x, y, z or w component of the four-component vector lookup result for each texel, respectively. and if you don't specify comp? it's treated as 0, selecting the x component of each texel to generate the result. default behaviour, iconic behaviour 😌

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🌈 VERSION SUPPORT 🌈

the big question: does your GLSL version even have this? let's find out. the function name is textureGatherOffset and here's the tea per OpenGL Shading Language Version:

• 1.10 — - nope 💀
• 1.20 — - nope 💀
• 1.30 — - nope 💀
• 1.40 — - nope 💀
• 1.50 — - nope 💀
• 3.30 — - nope 💀
• 4.00 — ✔ oh we're SO back 👑
• 4.10 — ✔ yes bestie ✅
• 4.20 — ✔ yes bestie ✅
• 4.30 — ✔ yes bestie ✅
• 4.40 — ✔ yes bestie ✅
• 4.50 — ✔ yes bestie ✅

so if you're on anything below 4.00, this function simply does not know you. it's not personal. it's just versioning 😭

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🦋 SEE ALSO 🦋

the whole friend group, go say hi:

• texelFetch()
• texelFetchOffset()
• texture()
• textureGather()
• textureGatherOffsets()
• textureGrad()
• textureGradOffset()
• textureLod()
• textureLodOffset()
• textureOffset()
• textureProj()
• textureProjGrad()
• textureProjGradOffset()
• textureProjLod()
• textureProjLodOffset()
• textureProjOffset()
• textureQueryLod()
• textureSize()

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👑 COPYRIGHT 👑

Copyright © 2011-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.

Copyright © 2011-2014 Khronos Group

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okay that's the whole page, you ate it, I'm obsessed 💖 this was TEXTUREGATHEROFFSET(3G) brought to you from [FIXME: source], dated 01/03/2018 — and [FIXME: manual] is literally where it came from, we love a mysterious source. mwah, go gather some texels bestie 🎀✨🦋