Even more compatibility.

src/main/java/com/simibubi/create/foundation/render/backend/Backend.java

@@ -3,15 +3,12 @@ package com.simibubi.create.foundation.render.backend;
 import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.nio.ByteBuffer;
 import java.nio.FloatBuffer;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.function.Consumer;
 import java.util.function.Predicate;
 
-import com.simibubi.create.foundation.render.backend.gl.versioned.GlFunctions;
+import com.simibubi.create.foundation.render.backend.gl.versioned.GlFeatureCompat;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.lwjgl.opengl.GL;
@@ -23,8 +20,6 @@ import com.simibubi.create.foundation.render.backend.gl.shader.GlProgram;
 import com.simibubi.create.foundation.render.backend.gl.shader.GlShader;
 import com.simibubi.create.foundation.render.backend.gl.shader.ProgramSpec;
 import com.simibubi.create.foundation.render.backend.gl.shader.ShaderType;
-import com.simibubi.create.foundation.render.backend.gl.versioned.GlVersioned;
-import com.simibubi.create.foundation.render.backend.gl.versioned.MapBuffer;
 
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.texture.TextureUtil;
@@ -45,7 +40,7 @@ public class Backend {
     private static boolean enabled;
 
     public static GLCapabilities capabilities;
-    public static GlFunctions functions;
+    public static GlFeatureCompat compat;
 
     public Backend() {
         throw new IllegalStateException();
@@ -74,9 +69,9 @@ public class Backend {
 
     public static boolean canUseInstancing() {
         return enabled &&
-                functions.vertexArrayObjectsSupported() &&
+                compat.vertexArrayObjectsSupported() &&
-                functions.drawInstancedSupported() &&
+                compat.drawInstancedSupported() &&
-                functions.instancedArraysSupported();
+                compat.instancedArraysSupported();
     }
 
     public static boolean canUseVBOs() {
@@ -107,7 +102,7 @@ public class Backend {
     private static void onResourceManagerReload(IResourceManager manager, Predicate<IResourceType> predicate) {
         if (predicate.test(VanillaResourceType.SHADERS)) {
             capabilities = GL.createCapabilities();
-            functions = new GlFunctions(capabilities);
+            compat = new GlFeatureCompat(capabilities);
 
             OptifineHandler.refresh();
             refresh();

src/main/java/com/simibubi/create/foundation/render/backend/gl/GlBuffer.java

@@ -4,7 +4,6 @@ import java.nio.ByteBuffer;
 import java.util.function.Consumer;
 
 import com.simibubi.create.foundation.render.backend.Backend;
-import com.simibubi.create.foundation.render.backend.gl.versioned.GlFunctions;
 import org.lwjgl.opengl.GL20;
 
 public class GlBuffer extends GlObject {
@@ -35,11 +34,11 @@ public class GlBuffer extends GlObject {
     }
 
     public void map(int length, Consumer<ByteBuffer> upload) {
-        Backend.functions.mapBuffer(bufferType, 0, length, upload);
+        Backend.compat.mapBuffer(bufferType, 0, length, upload);
     }
 
     public void map(int offset, int length, Consumer<ByteBuffer> upload) {
-        Backend.functions.mapBuffer(bufferType, offset, length, upload);
+        Backend.compat.mapBuffer(bufferType, offset, length, upload);
     }
 
     protected void deleteInternal(int handle) {

src/main/java/com/simibubi/create/foundation/render/backend/gl/GlVertexArray.java

@@ -3,19 +3,18 @@ package com.simibubi.create.foundation.render.backend.gl;
 import java.util.function.Consumer;
 
 import com.simibubi.create.foundation.render.backend.Backend;
-import org.lwjgl.opengl.GL30;
 
 public class GlVertexArray extends GlObject {
     public GlVertexArray() {
-        setHandle(Backend.functions.genVertexArrays());
+        setHandle(Backend.compat.genVertexArrays());
     }
 
     public void bind() {
-        Backend.functions.bindVertexArray(handle());
+        Backend.compat.bindVertexArray(handle());
     }
 
     public void unbind() {
-        Backend.functions.bindVertexArray(0);
+        Backend.compat.bindVertexArray(0);
     }
 
     public void with(Consumer<GlVertexArray> action) {
@@ -25,6 +24,6 @@ public class GlVertexArray extends GlObject {
     }
 
     protected void deleteInternal(int handle) {
-        Backend.functions.deleteVertexArrays(handle);
+        Backend.compat.deleteVertexArrays(handle);
     }
 }

src/main/java/com/simibubi/create/foundation/render/backend/gl/versioned/GlFeatureCompat.java

@@ -13,19 +13,23 @@ import java.util.function.Consumer;
  * Each field stores an enum variant that provides access to the
  * most appropriate version of a feature for the current system.
  */
-public class GlFunctions {
+public class GlFeatureCompat {
     public final MapBuffer mapBuffer;
 
     public final VertexArrayObject vertexArrayObject;
     public final InstancedArrays instancedArrays;
     public final DrawInstanced drawInstanced;
 
-    public GlFunctions(GLCapabilities caps) {
+    public final RGPixelFormat pixelFormat;
+
+    public GlFeatureCompat(GLCapabilities caps) {
         mapBuffer = getLatest(MapBuffer.class, caps);
 
         vertexArrayObject = getLatest(VertexArrayObject.class, caps);
         instancedArrays = getLatest(InstancedArrays.class, caps);
         drawInstanced = getLatest(DrawInstanced.class, caps);
+
+        pixelFormat = getLatest(RGPixelFormat.class, caps);
     }
 
     public void mapBuffer(int target, int offset, int length, Consumer<ByteBuffer> upload) {

src/main/java/com/simibubi/create/foundation/render/backend/gl/versioned/RGPixelFormat.java

@@ -0,0 +1,75 @@
+package com.simibubi.create.foundation.render.backend.gl.versioned;
+
+import org.lwjgl.opengl.*;
+
+public enum RGPixelFormat implements GlVersioned {
+    GL30_RG {
+        @Override
+        public boolean supported(GLCapabilities caps) {
+            return caps.OpenGL30;
+        }
+
+        @Override
+        public int internalFormat() {
+            return GL30.GL_RG8;
+        }
+
+        @Override
+        public int format() {
+            return GL30.GL_RG;
+        }
+
+        @Override
+        public int byteCount() {
+            return 2;
+        }
+    },
+    GL11_RGB {
+        @Override
+        public boolean supported(GLCapabilities caps) {
+            return caps.OpenGL11;
+        }
+
+        @Override
+        public int internalFormat() {
+            return GL11.GL_RGB8;
+        }
+
+        @Override
+        public int format() {
+            return GL11.GL_RGB;
+        }
+
+        @Override
+        public int byteCount() {
+            return 3;
+        }
+    },
+    UNSUPPORTED {
+        @Override
+        public boolean supported(GLCapabilities caps) {
+            return true;
+        }
+
+        @Override
+        public int internalFormat() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public int format() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public int byteCount() {
+            throw new UnsupportedOperationException();
+        }
+    }
+
+    ;
+
+    public abstract int internalFormat();
+    public abstract int format();
+    public abstract int byteCount();
+}

src/main/java/com/simibubi/create/foundation/render/backend/instancing/InstancedModel.java

@@ -115,7 +115,7 @@ public abstract class InstancedModel<D extends InstanceData> extends BufferedMod
     protected void doRender() {
         vao.with(vao -> {
             renderSetup();
-            Backend.functions.drawArraysInstanced(GL11.GL_QUADS, 0, vertexCount, glInstanceCount);
+            Backend.compat.drawArraysInstanced(GL11.GL_QUADS, 0, vertexCount, glInstanceCount);
         });
     }
 
@@ -162,7 +162,7 @@ public abstract class InstancedModel<D extends InstanceData> extends BufferedMod
             instanceFormat.vertexAttribPointers(staticAttributes);
 
             for (int i = 0; i < instanceFormat.getShaderAttributeCount(); i++) {
-                Backend.functions.vertexAttribDivisor(i + staticAttributes, 1);
+                Backend.compat.vertexAttribDivisor(i + staticAttributes, 1);
             }
         });
 

src/main/java/com/simibubi/create/foundation/render/backend/light/LightVolume.java

@@ -2,11 +2,12 @@ package com.simibubi.create.foundation.render.backend.light;
 
 import java.nio.ByteBuffer;
 
+import com.simibubi.create.foundation.render.backend.Backend;
+import com.simibubi.create.foundation.render.backend.gl.versioned.RGPixelFormat;
 import org.lwjgl.opengl.GL11;
 import org.lwjgl.opengl.GL12;
 import org.lwjgl.opengl.GL13;
 import org.lwjgl.opengl.GL20;
-import org.lwjgl.opengl.GL40;
 import org.lwjgl.system.MemoryUtil;
 
 import com.simibubi.create.foundation.render.backend.RenderWork;
@@ -28,11 +29,15 @@ public class LightVolume {
 
     private final GlTexture glTexture;
 
+    private final RGPixelFormat pixelFormat;
+
     public LightVolume(GridAlignedBB sampleVolume) {
         setSampleVolume(sampleVolume);
 
+        pixelFormat = Backend.compat.pixelFormat;
+
         this.glTexture = new GlTexture(GL20.GL_TEXTURE_3D);
-        this.lightData = MemoryUtil.memAlloc(this.textureVolume.volume() * 2); // TODO: reduce this to span only sampleVolume
+        this.lightData = MemoryUtil.memAlloc(this.textureVolume.volume() * pixelFormat.byteCount());
 
         // allocate space for the texture
         GL20.glActiveTexture(GL20.GL_TEXTURE4);
@@ -41,7 +46,7 @@ public class LightVolume {
         int sizeX = textureVolume.sizeX();
         int sizeY = textureVolume.sizeY();
         int sizeZ = textureVolume.sizeZ();
-        GL12.glTexImage3D(GL12.GL_TEXTURE_3D, 0, GL40.GL_RG8, sizeX, sizeY, sizeZ, 0, GL40.GL_RG, GL40.GL_UNSIGNED_BYTE, 0);
+        GL12.glTexImage3D(GL12.GL_TEXTURE_3D, 0, pixelFormat.internalFormat(), sizeX, sizeY, sizeZ, 0, pixelFormat.format(), GL20.GL_UNSIGNED_BYTE, 0);
 
         glTexture.unbind();
         GL20.glActiveTexture(GL20.GL_TEXTURE0);
@@ -222,7 +227,7 @@ public class LightVolume {
         // just in case something goes wrong or we accidentally call this before this volume is properly disposed of.
         if (lightData == null || removed) return;
 
-        GL13.glActiveTexture(GL40.GL_TEXTURE4);
+        GL13.glActiveTexture(GL20.GL_TEXTURE4);
         glTexture.bind();
         GL11.glTexParameteri(GL13.GL_TEXTURE_3D, GL13.GL_TEXTURE_MIN_FILTER, GL13.GL_LINEAR);
         GL11.glTexParameteri(GL13.GL_TEXTURE_3D, GL13.GL_TEXTURE_MAG_FILTER, GL13.GL_LINEAR);
@@ -245,7 +250,7 @@ public class LightVolume {
             int sizeY = textureVolume.sizeY();
             int sizeZ = textureVolume.sizeZ();
 
-            GL12.glTexSubImage3D(GL12.GL_TEXTURE_3D, 0, 0, 0, 0, sizeX, sizeY, sizeZ, GL40.GL_RG, GL40.GL_UNSIGNED_BYTE, lightData);
+            GL12.glTexSubImage3D(GL12.GL_TEXTURE_3D, 0, 0, 0, 0, sizeX, sizeY, sizeZ, pixelFormat.format(), GL20.GL_UNSIGNED_BYTE, lightData);
 
             GL20.glPixelStorei(GL20.GL_UNPACK_ALIGNMENT, 4); // 4 is the default
             bufferDirty = false;
@@ -269,7 +274,7 @@ public class LightVolume {
         byte b = (byte) ((block & 0xF) << 4);
         byte s = (byte) ((sky & 0xF) << 4);
 
-        int i = index(x, y, z);
+        int i = posToIndex(x, y, z);
         lightData.put(i, b);
         lightData.put(i + 1, s);
     }
@@ -277,16 +282,16 @@ public class LightVolume {
     private void writeBlock(int x, int y, int z, int block) {
         byte b = (byte) ((block & 0xF) << 4);
 
-        lightData.put(index(x, y, z), b);
+        lightData.put(posToIndex(x, y, z), b);
     }
 
     private void writeSky(int x, int y, int z, int sky) {
         byte b = (byte) ((sky & 0xF) << 4);
 
-        lightData.put(index(x, y, z) + 1, b);
+        lightData.put(posToIndex(x, y, z) + 1, b);
     }
 
-    private int index(int x, int y, int z) {
+    private int posToIndex(int x, int y, int z) {
-        return (x + textureVolume.sizeX() * (y + z * textureVolume.sizeY())) * 2;
+        return (x + textureVolume.sizeX() * (y + z * textureVolume.sizeY())) * pixelFormat.byteCount();
     }
 }