From e7a88bfe1e77447306cc87d6a40af5d46cd641d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89ric=20Renaud-Houde?= <eric.renaud.houde@gmail.com>
Date: Sun, 30 Oct 2022 15:52:02 -0400
Subject: [PATCH] Enforce GL_NEAREST with gpu tetrahedral interpolation, fixing
 #1676. (#1708)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Eric Renaud-Houde <eric.renaud.houde@gmail.com>

Signed-off-by: Eric Renaud-Houde <eric.renaud.houde@gmail.com>
Co-authored-by: Rémi Achard <remiachard@gmail.com>
---
 src/OpenColorIO/ops/lut3d/Lut3DOpGPU.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/OpenColorIO/ops/lut3d/Lut3DOpGPU.cpp b/src/OpenColorIO/ops/lut3d/Lut3DOpGPU.cpp
index c521468c77..786f52961c 100644
--- a/src/OpenColorIO/ops/lut3d/Lut3DOpGPU.cpp
+++ b/src/OpenColorIO/ops/lut3d/Lut3DOpGPU.cpp
@@ -32,11 +32,17 @@ void GetLut3DGPUShaderProgram(GpuShaderCreatorRcPtr & shaderCreator, ConstLut3DO
     std::string name(resName.str());
     StringUtils::ReplaceInPlace(name, "__", "_");
 
+    Interpolation samplerInterpolation = lutData->getConcreteInterpolation();
+    // Enforce GL_NEAREST with shader-generated tetrahedral interpolation.
+    if (samplerInterpolation == INTERP_TETRAHEDRAL)
+    {
+        samplerInterpolation = INTERP_NEAREST;
+    }
     // (Using CacheID here to potentially allow reuse of existing textures.)
     shaderCreator->add3DTexture(name.c_str(),
                                 GpuShaderText::getSamplerName(name).c_str(),
                                 lutData->getGridSize(),
-                                lutData->getConcreteInterpolation(),
+                                samplerInterpolation,
                                 &lutData->getArray()[0]);
 
     {