avoid 'glGet's at all costs

src/main/java/com/simibubi/create/foundation/mixin/FogColorTrackerMixin.java

@@ -0,0 +1,20 @@
+package com.simibubi.create.foundation.mixin;
+
+import com.mojang.blaze3d.platform.GlStateManager;
+import com.simibubi.create.foundation.render.backend.gl.GlFog;
+import org.lwjgl.opengl.GL11;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(GlStateManager.class)
+public class FogColorTrackerMixin {
+
+    @Inject(at = @At("TAIL"), method = "fog")
+    private static void copyFogColor(int pname, float[] params, CallbackInfo ci) {
+        if (pname == GL11.GL_FOG_COLOR) {
+            GlFog.FOG_COLOR = params;
+        }
+    }
+}

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

@@ -47,8 +47,7 @@ public class BasicProgram extends GlProgram {
         GL20.glUniform3f(uCameraPos, camX, camY, camZ);
 
         GL20.glUniform2f(uFogRange, GlFog.getFogStart(), GlFog.getFogEnd());
-        GL20.glGetFloatv(GL20.GL_FOG_COLOR, Backend.VEC4_BUFFER);
-        GL20.glUniform4fv(uFogColor, Backend.VEC4_BUFFER);
+        GL20.glUniform4fv(uFogColor, GlFog.FOG_COLOR);
     }
 
     protected static void uploadMatrixUniform(int uniform, Matrix4f mat) {

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

@@ -1,13 +1,29 @@
 package com.simibubi.create.foundation.render.backend.gl;
 
+import com.mojang.blaze3d.platform.GlStateManager;
+import org.lwjgl.opengl.GL15;
 import org.lwjgl.opengl.GL20;
 
 public class GlFog {
+    public static float[] FOG_COLOR = new float[] {0, 0, 0, 0};
+
+    public static boolean fogEnabled() {
+        return GlStateManager.FOG.field_179049_a.field_179201_b;
+    }
+
+    public static int getFogMode() {
+        return GlStateManager.FOG.field_179047_b;
+    }
+
+    public static float getFogDensity() {
+        return GlStateManager.FOG.field_179048_c;
+    }
+
     public static float getFogEnd() {
-        return GL20.glGetFloat(GL20.GL_FOG_END);
+        return GlStateManager.FOG.field_179046_e;
     }
 
     public static float getFogStart() {
-        return GL20.glGetFloat(GL20.GL_FOG_START);
+        return GlStateManager.FOG.field_179045_d;
     }
 }

src/main/resources/META-INF/accesstransformer.cfg

@@ -32,4 +32,10 @@ public net.minecraft.client.Minecraft field_193996_ah #renderPartialTicksPaused
 # Functions needed to setup a projection matrix
 public net.minecraft.client.renderer.GameRenderer field_78529_t #rendererUpdateCount
 public net.minecraft.client.renderer.GameRenderer func_228380_a_(Lcom/mojang/blaze3d/matrix/MatrixStack;F)V #bobViewWhenHurt
-public net.minecraft.client.renderer.GameRenderer func_228383_b_(Lcom/mojang/blaze3d/matrix/MatrixStack;F)V #bobView
+public net.minecraft.client.renderer.GameRenderer func_228383_b_(Lcom/mojang/blaze3d/matrix/MatrixStack;F)V #bobView
+
+# Expose fog state to the public
+public com.mojang.blaze3d.platform.GlStateManager$FogState
+public com.mojang.blaze3d.platform.GlStateManager field_225663_h_ #FOG
+public com.mojang.blaze3d.platform.GlStateManager$BooleanState
+public com.mojang.blaze3d.platform.GlStateManager$BooleanState field_179201_b #field_179201_b

src/main/resources/create.mixins.json

@@ -3,7 +3,14 @@
     "package": "com.simibubi.create.foundation.mixin",
     "compatibilityLevel": "JAVA_8",
     "refmap": "create.refmap.json",
-    "client": ["OnRemoveTileMixin", "ShaderCloseMixin", "CancelTileEntityRenderMixin", "LightUpdateMixin", "RenderHooksMixin"],
+    "client": [
+        "OnRemoveTileMixin",
+        "ShaderCloseMixin",
+        "CancelTileEntityRenderMixin",
+        "LightUpdateMixin",
+        "RenderHooksMixin",
+        "FogColorTrackerMixin"
+    ],
     "injectors": {
         "defaultRequire": 1
     },