From 6be6cabb1222aa1c4a580282cc3c087da52ba6f9 Mon Sep 17 00:00:00 2001
From: Jonas Herzig <jonas@spark-squared.com>
Date: Mon, 8 Jun 2026 20:16:16 +0200
Subject: [PATCH] ShaderTransformer: Fix integer texture attributes

Minecraft uses integer formats (namely 16-bit signed integers) for its
secondary (light and overlay) textures in all its `VertexFormat`s.

Previously the ShaderTransformer, used to convert legacy OpenGL shaders
to more modern OpenGL, used to use the GLSL type `vec2` for all texture
attributes. This resulted in broken values being delivered to the shader
on modern versions (presumably because they're trying to interpret the
bytes representing integer values as floating point values).

This commit fixes the issue by using `ivec2` where the provided
VertexFormat contains an integer type for the attribute.
---
 root.gradle.kts                               |  2 +-
 .../universal/shader/ShaderTransformer.kt     | 41 +++++++++++++++++--
 versions/1.21-1.20.6.txt                      |  2 +
 versions/1.21.5-1.21.4.txt                    |  2 +
 4 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 versions/1.21-1.20.6.txt

diff --git a/root.gradle.kts b/root.gradle.kts
index 8abf04f5..3b94813e 100644
--- a/root.gradle.kts
+++ b/root.gradle.kts
@@ -79,7 +79,7 @@ preprocess {
     fabric12103.link(fabric12100)
     neoForge12100.link(fabric12100)
     forge12100.link(fabric12100)
-    fabric12100.link(fabric12006)
+    fabric12100.link(fabric12006, file("versions/1.21-1.20.6.txt"))
     neoForge12006.link(fabric12006)
     forge12006.link(fabric12006)
     fabric12006.link(fabric12004)
diff --git a/src/main/kotlin/gg/essential/universal/shader/ShaderTransformer.kt b/src/main/kotlin/gg/essential/universal/shader/ShaderTransformer.kt
index e9caf450..8349ef96 100644
--- a/src/main/kotlin/gg/essential/universal/shader/ShaderTransformer.kt
+++ b/src/main/kotlin/gg/essential/universal/shader/ShaderTransformer.kt
@@ -4,6 +4,11 @@ package gg.essential.universal.shader
 //$$ import gg.essential.universal.standalone.render.VertexFormat
 //#else
 import net.minecraft.client.renderer.vertex.VertexFormat
+import net.minecraft.client.renderer.vertex.VertexFormatElement
+
+//#if MC >= 26.2
+//$$ import com.mojang.blaze3d.GpuFormat
+//#endif
 //#endif
 
 internal class ShaderTransformer(private val vertexFormat: VertexFormat?, private val targetVersion: Int) {
@@ -55,12 +60,19 @@ internal class ShaderTransformer(private val vertexFormat: VertexFormat?, privat
             }
         }
         if (vert) {
+            //#if STANDALONE
+            //$$ fun uvVecType(index: Int) = "vec2"
+            //#else
+            fun uvVecType(index: Int) =
+                if (vertexFormat?.uvIsFloat(index) ?: true) "vec2" else "ivec2"
+            //#endif
+
             val newAttributes = mutableListOf<Pair<String, String>>()
             replaceAttribute(newAttributes, "gl_Vertex", "vec3", "uc_Position", replacement = "vec4(uc_Position, 1.0)")
             replaceAttribute(newAttributes, "gl_Color", "vec4")
-            replaceAttribute(newAttributes, "gl_MultiTexCoord0.st", "vec2", "uc_UV0")
-            replaceAttribute(newAttributes, "gl_MultiTexCoord1.st", "vec2", "uc_UV1")
-            replaceAttribute(newAttributes, "gl_MultiTexCoord2.st", "vec2", "uc_UV2")
+            replaceAttribute(newAttributes, "gl_MultiTexCoord0.st", uvVecType(0), "uc_UV0")
+            replaceAttribute(newAttributes, "gl_MultiTexCoord1.st", uvVecType(1), "uc_UV1")
+            replaceAttribute(newAttributes, "gl_MultiTexCoord2.st", uvVecType(2), "uc_UV2")
 
             if (vertexFormat != null) {
                 //#if MC>=11700 && !STANDALONE
@@ -147,6 +159,29 @@ internal class ShaderTransformer(private val vertexFormat: VertexFormat?, privat
     }
 }
 
+//#if !STANDALONE
+private fun VertexFormat.uvIsFloat(i: Int): Boolean =
+    //#if MC >= 26.2
+    //$$ this.getElement("UV$i")
+    //#elseif MC >= 26.1
+    //$$ this.elements.getOrNull(this.elementAttributeNames.indexOf("UV$i"))
+    //#else
+    this.elements
+        .asSequence()
+        .filter { it.usage == VertexFormatElement.EnumUsage.UV }
+        .elementAtOrNull(i)
+    //#endif
+        ?.isFloat()
+        ?: true
+
+private fun VertexFormatElement.isFloat() =
+    //#if MC >= 26.2
+    //$$ this.format == GpuFormat.RG16_FLOAT || this.format == GpuFormat.RG32_FLOAT
+    //#else
+    this.type == VertexFormatElement.EnumType.FLOAT
+    //#endif
+//#endif
+
 internal enum class UniformType(val typeName: String, val glslName: String, val default: IntArray) {
     Int1("int", "int", intArrayOf(0)),
     Float1("float", "float", intArrayOf(0)),
diff --git a/versions/1.21-1.20.6.txt b/versions/1.21-1.20.6.txt
new file mode 100644
index 00000000..52bc49a8
--- /dev/null
+++ b/versions/1.21-1.20.6.txt
@@ -0,0 +1,2 @@
+net.minecraft.client.render.VertexFormatElement type() getComponentType()
+net.minecraft.client.render.VertexFormatElement usage() getType()
diff --git a/versions/1.21.5-1.21.4.txt b/versions/1.21.5-1.21.4.txt
index 71df62d1..84cb4c6d 100644
--- a/versions/1.21.5-1.21.4.txt
+++ b/versions/1.21.5-1.21.4.txt
@@ -1,3 +1,5 @@
 com.mojang.blaze3d.vertex.VertexFormat net.minecraft.client.render.VertexFormat
 com.mojang.blaze3d.vertex.VertexFormat getElementAttributeNames() getAttributeNames()
+com.mojang.blaze3d.vertex.VertexFormatElement net.minecraft.client.render.VertexFormatElement
+com.mojang.blaze3d.vertex.VertexFormatElement$Type net.minecraft.client.render.VertexFormatElement$ComponentType
 com.mojang.blaze3d.opengl.GlStateManager com.mojang.blaze3d.platform.GlStateManager