GLSL to the max

- Always compile with highest supported GLSL version
- Allow indirect shaders to compile with as low as GLSL 420
- Fix GL extension checks for indirect
- Explicitly initialize GlCompat as early as possible to avoid invalid
initialization off render thread

src/main/java/com/jozufozu/flywheel/backend/Backends.java

@@ -17,7 +17,7 @@ public final class Backends {
 	 */
 	public static final Backend INSTANCING = SimpleBackend.builder()
 			.engineFactory(level -> new EngineImpl(new InstancedDrawManager(InstancingPrograms.get()), 256))
-			.supported(() -> !ShadersModHandler.isShaderPackInUse() && GlCompat.supportsInstancing() && InstancingPrograms.allLoaded())
+			.supported(() -> GlCompat.SUPPORTS_INSTANCING && InstancingPrograms.allLoaded() && !ShadersModHandler.isShaderPackInUse())
 			.register(Flywheel.rl("instancing"));
 
 	/**
@@ -26,7 +26,7 @@ public final class Backends {
 	public static final Backend INDIRECT = SimpleBackend.builder()
 			.engineFactory(level -> new EngineImpl(new IndirectDrawManager(IndirectPrograms.get()), 256))
 			.fallback(() -> Backends.INSTANCING)
-			.supported(() -> !ShadersModHandler.isShaderPackInUse() && GlCompat.supportsIndirect() && IndirectPrograms.allLoaded())
+			.supported(() -> GlCompat.SUPPORTS_INDIRECT && IndirectPrograms.allLoaded() && !ShadersModHandler.isShaderPackInUse())
 			.register(Flywheel.rl("indirect"));
 
 	private Backends() {

src/main/java/com/jozufozu/flywheel/backend/compile/IndirectPrograms.java

@@ -1,5 +1,6 @@
 package com.jozufozu.flywheel.backend.compile;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
@@ -33,6 +34,9 @@ public class IndirectPrograms extends AtomicReferenceCounted {
 	private static final Compile<InstanceType<?>> CULL = new Compile<>();
 	private static final Compile<ResourceLocation> UTIL = new Compile<>();
 
+	private static final List<String> EXTENSIONS = getExtensions(GlCompat.MAX_GLSL_VERSION);
+	private static final List<String> COMPUTE_EXTENSIONS = getComputeExtensions(GlCompat.MAX_GLSL_VERSION);
+
 	@Nullable
 	private static IndirectPrograms instance;
 
@@ -48,10 +52,33 @@ public class IndirectPrograms extends AtomicReferenceCounted {
 		this.scatter = scatter;
 	}
 
+	private static List<String> getExtensions(GlslVersion glslVersion) {
+		List<String> extensions = new ArrayList<>();
+		if (glslVersion.compareTo(GlslVersion.V430) < 0) {
+			extensions.add("GL_ARB_shader_storage_buffer_object");
+		}
+		if (glslVersion.compareTo(GlslVersion.V460) < 0) {
+			extensions.add("GL_ARB_shader_draw_parameters");
+		}
+		return extensions;
+	}
+
+	private static List<String> getComputeExtensions(GlslVersion glslVersion) {
+		List<String> extensions = new ArrayList<>();
+		if (glslVersion.compareTo(GlslVersion.V430) < 0) {
+			extensions.add("GL_ARB_compute_shader");
+		}
+		return extensions;
+	}
+
 	static void reload(ShaderSources sources, ImmutableList<PipelineProgramKey> pipelineKeys, List<SourceComponent> vertexComponents, List<SourceComponent> fragmentComponents) {
+		if (!GlCompat.SUPPORTS_INDIRECT) {
+			return;
+		}
+
 		IndirectPrograms newInstance = null;
 
-		var pipelineCompiler = PipelineCompiler.create(sources, Pipelines.INDIRECT, vertexComponents, fragmentComponents);
+		var pipelineCompiler = PipelineCompiler.create(sources, Pipelines.INDIRECT, vertexComponents, fragmentComponents, EXTENSIONS);
 		var cullingCompiler = createCullingCompiler(sources);
 		var applyCompiler = createUtilCompiler(sources);
 
@@ -76,8 +103,10 @@ public class IndirectPrograms extends AtomicReferenceCounted {
 
 	private static CompilationHarness<InstanceType<?>> createCullingCompiler(ShaderSources sources) {
 		return CULL.program()
-				.link(CULL.shader(GlslVersion.V460, ShaderType.COMPUTE)
+				.link(CULL.shader(GlCompat.MAX_GLSL_VERSION, ShaderType.COMPUTE)
 						.nameMapper(instanceType -> "culling/" + ResourceUtil.toDebugFileNameNoExtension(instanceType.cullShader()))
+						.enableExtensions(EXTENSIONS)
+						.enableExtensions(COMPUTE_EXTENSIONS)
 						.define("_FLW_SUBGROUP_SIZE", GlCompat.SUBGROUP_SIZE)
 						.withResource(CULL_SHADER_API_IMPL)
 						.withComponent(InstanceStructComponent::new)
@@ -96,8 +125,10 @@ public class IndirectPrograms extends AtomicReferenceCounted {
 
 	private static CompilationHarness<ResourceLocation> createUtilCompiler(ShaderSources sources) {
 		return UTIL.program()
-				.link(UTIL.shader(GlslVersion.V460, ShaderType.COMPUTE)
+				.link(UTIL.shader(GlCompat.MAX_GLSL_VERSION, ShaderType.COMPUTE)
 						.nameMapper(resourceLocation -> "utilities/" + ResourceUtil.toDebugFileNameNoExtension(resourceLocation))
+						.enableExtensions(EXTENSIONS)
+						.enableExtensions(COMPUTE_EXTENSIONS)
 						.define("_FLW_SUBGROUP_SIZE", GlCompat.SUBGROUP_SIZE)
 						.withResource(s -> s))
 				.harness("utilities", sources);

src/main/java/com/jozufozu/flywheel/backend/compile/InstancingPrograms.java

@@ -7,6 +7,7 @@ import org.jetbrains.annotations.Nullable;
 
 import com.google.common.collect.ImmutableList;
 import com.jozufozu.flywheel.api.instance.InstanceType;
+import com.jozufozu.flywheel.backend.gl.GlCompat;
 import com.jozufozu.flywheel.backend.gl.shader.GlProgram;
 import com.jozufozu.flywheel.backend.glsl.ShaderSources;
 import com.jozufozu.flywheel.backend.glsl.SourceComponent;
@@ -23,6 +24,10 @@ public class InstancingPrograms extends AtomicReferenceCounted {
 	}
 
 	static void reload(ShaderSources sources, ImmutableList<PipelineProgramKey> pipelineKeys, List<SourceComponent> vertexComponents, List<SourceComponent> fragmentComponents) {
+		if (!GlCompat.SUPPORTS_INSTANCING) {
+			return;
+		}
+
 		InstancingPrograms newInstance = null;
 
 		var pipelineCompiler = PipelineCompiler.create(sources, Pipelines.INSTANCING, vertexComponents, fragmentComponents);

src/main/java/com/jozufozu/flywheel/backend/compile/Pipeline.java

@@ -8,12 +8,11 @@ import org.jetbrains.annotations.Nullable;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.instance.InstanceType;
 import com.jozufozu.flywheel.backend.gl.shader.GlProgram;
-import com.jozufozu.flywheel.backend.glsl.GlslVersion;
 import com.jozufozu.flywheel.backend.glsl.SourceComponent;
 
 import net.minecraft.resources.ResourceLocation;
 
-public record Pipeline(GlslVersion glslVersion, ResourceLocation vertexMain, ResourceLocation fragmentMain,
+public record Pipeline(ResourceLocation vertexMain, ResourceLocation fragmentMain,
 					   InstanceAssembler assembler, String compilerMarker, Consumer<GlProgram> onLink) {
 
 	@FunctionalInterface
@@ -31,8 +30,6 @@ public record Pipeline(GlslVersion glslVersion, ResourceLocation vertexMain, Res
 	}
 
 	public static class Builder {
-		@Nullable
-		private GlslVersion glslVersion;
 		@Nullable
 		private ResourceLocation vertexMain;
 		@Nullable
@@ -44,11 +41,6 @@ public record Pipeline(GlslVersion glslVersion, ResourceLocation vertexMain, Res
 		@Nullable
 		private Consumer<GlProgram> onLink;
 
-		public Builder glslVersion(GlslVersion glslVersion) {
-			this.glslVersion = glslVersion;
-			return this;
-		}
-
 		public Builder vertexMain(ResourceLocation shader) {
 			this.vertexMain = shader;
 			return this;
@@ -75,13 +67,12 @@ public record Pipeline(GlslVersion glslVersion, ResourceLocation vertexMain, Res
 		}
 
 		public Pipeline build() {
-			Objects.requireNonNull(glslVersion);
 			Objects.requireNonNull(vertexMain);
 			Objects.requireNonNull(fragmentMain);
 			Objects.requireNonNull(assembler);
 			Objects.requireNonNull(compilerMarker);
 			Objects.requireNonNull(onLink);
-			return new Pipeline(glslVersion, vertexMain, fragmentMain, assembler, compilerMarker, onLink);
+			return new Pipeline(vertexMain, fragmentMain, assembler, compilerMarker, onLink);
 		}
 	}
 }

src/main/java/com/jozufozu/flywheel/backend/compile/PipelineCompiler.java

@@ -1,5 +1,7 @@
 package com.jozufozu.flywheel.backend.compile;
 
+import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import com.jozufozu.flywheel.Flywheel;
@@ -9,6 +11,7 @@ import com.jozufozu.flywheel.backend.compile.component.InstanceStructComponent;
 import com.jozufozu.flywheel.backend.compile.core.CompilationHarness;
 import com.jozufozu.flywheel.backend.compile.core.Compile;
 import com.jozufozu.flywheel.backend.engine.uniform.Uniforms;
+import com.jozufozu.flywheel.backend.gl.GlCompat;
 import com.jozufozu.flywheel.backend.gl.shader.GlProgram;
 import com.jozufozu.flywheel.backend.gl.shader.ShaderType;
 import com.jozufozu.flywheel.backend.glsl.ShaderSources;
@@ -23,9 +26,9 @@ public final class PipelineCompiler {
 	private static final ResourceLocation API_IMPL_VERT = Flywheel.rl("internal/api_impl.vert");
 	private static final ResourceLocation API_IMPL_FRAG = Flywheel.rl("internal/api_impl.frag");
 
-	static CompilationHarness<PipelineProgramKey> create(ShaderSources sources, Pipeline pipeline, List<SourceComponent> vertexComponents, List<SourceComponent> fragmentComponents) {
+	static CompilationHarness<PipelineProgramKey> create(ShaderSources sources, Pipeline pipeline, List<SourceComponent> vertexComponents, List<SourceComponent> fragmentComponents, Collection<String> extensions) {
 		return PIPELINE.program()
-				.link(PIPELINE.shader(pipeline.glslVersion(), ShaderType.VERTEX)
+				.link(PIPELINE.shader(GlCompat.MAX_GLSL_VERSION, ShaderType.VERTEX)
 						.nameMapper(key -> {
 							var instance = ResourceUtil.toDebugFileNameNoExtension(key.instanceType()
 									.vertexShader());
@@ -34,6 +37,7 @@ public final class PipelineCompiler {
 									.nameLowerCase();
 							return "pipeline/" + pipeline.compilerMarker() + "/" + instance + "_" + context;
 						})
+						.enableExtensions(extensions)
 						.onCompile((key, comp) -> key.contextShader()
 								.onCompile(comp))
 						.withResource(API_IMPL_VERT)
@@ -45,12 +49,13 @@ public final class PipelineCompiler {
 						.withComponent(key -> pipeline.assembler()
 								.assemble(key.instanceType()))
 						.withResource(pipeline.vertexMain()))
-				.link(PIPELINE.shader(pipeline.glslVersion(), ShaderType.FRAGMENT)
+				.link(PIPELINE.shader(GlCompat.MAX_GLSL_VERSION, ShaderType.FRAGMENT)
 						.nameMapper(key -> {
 							var context = key.contextShader()
 									.nameLowerCase();
 							return "pipeline/" + pipeline.compilerMarker() + "/" + context;
 						})
+						.enableExtensions(extensions)
 						.enableExtension("GL_ARB_conservative_depth")
 						.onCompile((key, comp) -> key.contextShader()
 								.onCompile(comp))
@@ -86,4 +91,8 @@ public final class PipelineCompiler {
 				})
 				.harness(pipeline.compilerMarker(), sources);
 	}
+
+	static CompilationHarness<PipelineProgramKey> create(ShaderSources sources, Pipeline pipeline, List<SourceComponent> vertexComponents, List<SourceComponent> fragmentComponents) {
+		return create(sources, pipeline, vertexComponents, fragmentComponents, Collections.emptyList());
+	}
 }

src/main/java/com/jozufozu/flywheel/backend/compile/Pipelines.java

@@ -4,12 +4,10 @@ import com.jozufozu.flywheel.Flywheel;
 import com.jozufozu.flywheel.backend.Samplers;
 import com.jozufozu.flywheel.backend.compile.component.BufferTextureInstanceComponent;
 import com.jozufozu.flywheel.backend.compile.component.SsboInstanceComponent;
-import com.jozufozu.flywheel.backend.glsl.GlslVersion;
 
 public final class Pipelines {
 	public static final Pipeline INSTANCING = Pipeline.builder()
 			.compilerMarker("instancing")
-			.glslVersion(GlslVersion.V330)
 			.vertexMain(Flywheel.rl("internal/instancing/main.vert"))
 			.fragmentMain(Flywheel.rl("internal/instancing/main.frag"))
 			.assembler(BufferTextureInstanceComponent::new)
@@ -18,7 +16,6 @@ public final class Pipelines {
 
 	public static final Pipeline INDIRECT = Pipeline.builder()
 			.compilerMarker("indirect")
-			.glslVersion(GlslVersion.V460)
 			.vertexMain(Flywheel.rl("internal/indirect/main.vert"))
 			.fragmentMain(Flywheel.rl("internal/indirect/main.frag"))
 			.assembler(SsboInstanceComponent::new)

src/main/java/com/jozufozu/flywheel/backend/compile/core/Compile.java

@@ -40,6 +40,100 @@ public class Compile<K> {
 		return new ProgramStitcher<>();
 	}
 
+	public static class ShaderCompiler<K> {
+		private final GlslVersion glslVersion;
+		private final ShaderType shaderType;
+		private final List<BiFunction<K, SourceLoader, @Nullable SourceComponent>> fetchers = new ArrayList<>();
+		private BiConsumer<K, Compilation> compilationCallbacks = ($, $$) -> {
+		};
+		private Function<K, String> nameMapper = Object::toString;
+
+		public ShaderCompiler(GlslVersion glslVersion, ShaderType shaderType) {
+			this.glslVersion = glslVersion;
+			this.shaderType = shaderType;
+		}
+
+		public ShaderCompiler<K> nameMapper(Function<K, String> nameMapper) {
+			this.nameMapper = nameMapper;
+			return this;
+		}
+
+		public ShaderCompiler<K> with(BiFunction<K, SourceLoader, @Nullable SourceComponent> fetch) {
+			fetchers.add(fetch);
+			return this;
+		}
+
+		public ShaderCompiler<K> withComponents(Collection<@Nullable SourceComponent> components) {
+			components.forEach(this::withComponent);
+			return this;
+		}
+
+		public ShaderCompiler<K> withComponent(@Nullable SourceComponent component) {
+			return withComponent($ -> component);
+		}
+
+		public ShaderCompiler<K> withComponent(Function<K, @Nullable SourceComponent> sourceFetcher) {
+			return with((key, $) -> sourceFetcher.apply(key));
+		}
+
+		public ShaderCompiler<K> withResource(Function<K, ResourceLocation> sourceFetcher) {
+			return with((key, loader) -> loader.find(sourceFetcher.apply(key)));
+		}
+
+		public ShaderCompiler<K> withResource(ResourceLocation resourceLocation) {
+			return withResource($ -> resourceLocation);
+		}
+
+		public ShaderCompiler<K> onCompile(BiConsumer<K, Compilation> cb) {
+			compilationCallbacks = compilationCallbacks.andThen(cb);
+			return this;
+		}
+
+		public ShaderCompiler<K> define(String def, int value) {
+			return onCompile(($, ctx) -> ctx.define(def, String.valueOf(value)));
+		}
+
+		public ShaderCompiler<K> enableExtension(String extension) {
+			return onCompile(($, ctx) -> ctx.enableExtension(extension));
+		}
+
+		public ShaderCompiler<K> enableExtensions(String... extensions) {
+			return onCompile(($, ctx) -> {
+				for (String extension : extensions) {
+					ctx.enableExtension(extension);
+				}
+			});
+		}
+
+		public ShaderCompiler<K> enableExtensions(Collection<String> extensions) {
+			return onCompile(($, ctx) -> {
+				for (String extension : extensions) {
+					ctx.enableExtension(extension);
+				}
+			});
+		}
+
+		@Nullable
+		private GlShader compile(K key, ShaderCache compiler, SourceLoader loader) {
+			var components = new ArrayList<SourceComponent>();
+			boolean ok = true;
+			for (var fetcher : fetchers) {
+				SourceComponent apply = fetcher.apply(key, loader);
+				if (apply == null) {
+					ok = false;
+				}
+				components.add(apply);
+			}
+
+			if (!ok) {
+				return null;
+			}
+
+			Consumer<Compilation> cb = ctx -> compilationCallbacks.accept(key, ctx);
+			return compiler.compile(glslVersion, shaderType, nameMapper.apply(key), cb, components);
+		}
+	}
+
 	public static class ProgramStitcher<K> implements CompilationHarness.KeyCompiler<K> {
 		private final Map<ShaderType, ShaderCompiler<K>> compilers = new EnumMap<>(ShaderType.class);
 		private BiConsumer<K, GlProgram> postLink = (k, p) -> {
@@ -100,82 +194,4 @@ public class Compile<K> {
 			return out;
 		}
 	}
-
-	public static class ShaderCompiler<K> {
-		private final GlslVersion glslVersion;
-		private final ShaderType shaderType;
-		private final List<BiFunction<K, SourceLoader, @Nullable SourceComponent>> fetchers = new ArrayList<>();
-		private BiConsumer<K, Compilation> compilationCallbacks = ($, $$) -> {
-		};
-		private Function<K, String> nameMapper = Object::toString;
-
-		public ShaderCompiler(GlslVersion glslVersion, ShaderType shaderType) {
-			this.glslVersion = glslVersion;
-			this.shaderType = shaderType;
-		}
-
-		public ShaderCompiler<K> nameMapper(Function<K, String> nameMapper) {
-			this.nameMapper = nameMapper;
-			return this;
-		}
-
-		public ShaderCompiler<K> with(BiFunction<K, SourceLoader, @Nullable SourceComponent> fetch) {
-			fetchers.add(fetch);
-			return this;
-		}
-
-		public ShaderCompiler<K> withComponents(Collection<@Nullable SourceComponent> components) {
-			components.forEach(this::withComponent);
-			return this;
-		}
-
-		public ShaderCompiler<K> withComponent(@Nullable SourceComponent component) {
-			return withComponent($ -> component);
-		}
-
-		public ShaderCompiler<K> withComponent(Function<K, @Nullable SourceComponent> sourceFetcher) {
-			return with((key, $) -> sourceFetcher.apply(key));
-		}
-
-		public ShaderCompiler<K> withResource(Function<K, ResourceLocation> sourceFetcher) {
-			return with((key, loader) -> loader.find(sourceFetcher.apply(key)));
-		}
-
-		public ShaderCompiler<K> withResource(ResourceLocation resourceLocation) {
-			return withResource($ -> resourceLocation);
-		}
-
-		public ShaderCompiler<K> onCompile(BiConsumer<K, Compilation> cb) {
-			compilationCallbacks = compilationCallbacks.andThen(cb);
-			return this;
-		}
-
-		public ShaderCompiler<K> define(String def, int value) {
-			return onCompile(($, ctx) -> ctx.define(def, String.valueOf(value)));
-		}
-
-		public ShaderCompiler<K> enableExtension(String extension) {
-			return onCompile(($, ctx) -> ctx.enableExtension(extension));
-		}
-
-		@Nullable
-		private GlShader compile(K key, ShaderCache compiler, SourceLoader loader) {
-			var components = new ArrayList<SourceComponent>();
-			boolean ok = true;
-			for (var fetcher : fetchers) {
-				SourceComponent apply = fetcher.apply(key, loader);
-				if (apply == null) {
-					ok = false;
-				}
-				components.add(apply);
-			}
-
-			if (!ok) {
-				return null;
-			}
-
-			Consumer<Compilation> cb = ctx -> compilationCallbacks.accept(key, ctx);
-			return compiler.compile(glslVersion, shaderType, nameMapper.apply(key), cb, components);
-		}
-	}
 }

src/main/java/com/jozufozu/flywheel/backend/gl/GlCompat.java

@@ -10,78 +10,23 @@ import org.lwjgl.opengl.GLCapabilities;
 import org.lwjgl.opengl.KHRShaderSubgroup;
 import org.lwjgl.system.MemoryStack;
 
+import com.jozufozu.flywheel.backend.glsl.GlslVersion;
 import com.jozufozu.flywheel.lib.math.MoreMath;
 
-import net.minecraft.Util;
-
-/**
- * An instance of this class stores information about what OpenGL features are available.
- * <br>
- * Each field stores an enum variant that provides access to the most appropriate version of a feature for the current
- * system.
- */
 public final class GlCompat {
-	public static final GLCapabilities CAPABILITIES = GL.createCapabilities();
+	public static final GLCapabilities CAPABILITIES = GL.getCapabilities();
-	public static final boolean WINDOWS = _decideIfWeAreWindows();
+	public static final Driver DRIVER = readVendorString();
+	public static final int SUBGROUP_SIZE = subgroupSize();
 	public static final boolean ALLOW_DSA = true;
-	public static final boolean SUPPORTS_INDIRECT = _decideIfWeSupportIndirect();
+	public static final GlslVersion MAX_GLSL_VERSION = maxGlslVersion();
-	public static final int SUBGROUP_SIZE = _subgroupSize();
+
-	public static final Driver DRIVER = _readVendorString();
+	public static final boolean SUPPORTS_INSTANCING = isInstancingSupported();
+	public static final boolean SUPPORTS_INDIRECT = isIndirectSupported();
 
 	private GlCompat() {
 	}
 
-	public static boolean onAMDWindows() {
+	public static void init() {
-		return DRIVER == Driver.AMD && WINDOWS;
-	}
-
-	public static boolean supportsInstancing() {
-		return true;
-	}
-
-	public static boolean supportsIndirect() {
-		return SUPPORTS_INDIRECT;
-	}
-
-	private static Driver _readVendorString() {
-		String vendor = GL20C.glGetString(GL20C.GL_VENDOR);
-
-		if (vendor == null) {
-			return Driver.UNKNOWN;
-		}
-
-		// vendor string I got was "ATI Technologies Inc."
-		if (vendor.contains("ATI") || vendor.contains("AMD")) {
-			return Driver.AMD;
-		} else if (vendor.contains("NVIDIA")) {
-			return Driver.NVIDIA;
-		} else if (vendor.contains("Intel")) {
-			return Driver.INTEL;
-		} else if (vendor.contains("Mesa")) {
-			return Driver.MESA;
-		}
-
-		return Driver.UNKNOWN;
-	}
-
-	private static boolean _decideIfWeAreWindows() {
-		return Util.getPlatform() == Util.OS.WINDOWS;
-	}
-
-	private static boolean _decideIfWeSupportIndirect() {
-		return CAPABILITIES.OpenGL46 || (CAPABILITIES.GL_ARB_compute_shader && CAPABILITIES.GL_ARB_shader_draw_parameters && CAPABILITIES.GL_ARB_base_instance && CAPABILITIES.GL_ARB_multi_draw_indirect && CAPABILITIES.GL_ARB_direct_state_access);
-	}
-
-	private static int _subgroupSize() {
-		if (CAPABILITIES.GL_KHR_shader_subgroup) {
-			return GL31C.glGetInteger(KHRShaderSubgroup.GL_SUBGROUP_SIZE_KHR);
-		}
-		// Try to guess.
-		// Newer (RDNA) AMD cards have 32 threads in a wavefront, older ones have 64.
-		// I assume the newer drivers will implement the above extension, so 64 is a
-		// reasonable guess for AMD hardware. In the worst case we'll just spread
-		// load across multiple SIMDs
-		return DRIVER == Driver.AMD || DRIVER == Driver.MESA ? 64 : 32;
 	}
 
 	public static int getComputeGroupCount(int invocations) {
@@ -108,5 +53,83 @@ public final class GlCompat {
 			GL20C.nglShaderSource(glId, 1, pointers.address0(), 0);
 		}
 	}
-}
 
+	private static Driver readVendorString() {
+		String vendor = GL20C.glGetString(GL20C.GL_VENDOR);
+
+		if (vendor == null) {
+			return Driver.UNKNOWN;
+		}
+
+		// vendor string I got was "ATI Technologies Inc."
+		if (vendor.contains("ATI") || vendor.contains("AMD")) {
+			return Driver.AMD;
+		} else if (vendor.contains("NVIDIA")) {
+			return Driver.NVIDIA;
+		} else if (vendor.contains("Intel")) {
+			return Driver.INTEL;
+		} else if (vendor.contains("Mesa")) {
+			return Driver.MESA;
+		}
+
+		return Driver.UNKNOWN;
+	}
+
+	private static int subgroupSize() {
+		if (CAPABILITIES.GL_KHR_shader_subgroup) {
+			return GL31C.glGetInteger(KHRShaderSubgroup.GL_SUBGROUP_SIZE_KHR);
+		}
+
+		// Try to guess.
+		// Newer (RDNA) AMD cards have 32 threads in a wavefront, older ones have 64.
+		// I assume the newer drivers will implement the above extension, so 64 is a
+		// reasonable guess for AMD hardware. In the worst case we'll just spread
+		// load across multiple SIMDs
+		return DRIVER == Driver.AMD || DRIVER == Driver.MESA ? 64 : 32;
+	}
+
+	private static GlslVersion maxGlslVersion() {
+		if (CAPABILITIES.OpenGL46) {
+			return GlslVersion.V460;
+		} else if (CAPABILITIES.OpenGL45) {
+			return GlslVersion.V450;
+		} else if (CAPABILITIES.OpenGL44) {
+			return GlslVersion.V440;
+		} else if (CAPABILITIES.OpenGL43) {
+			return GlslVersion.V430;
+		} else if (CAPABILITIES.OpenGL42) {
+			return GlslVersion.V420;
+		} else if (CAPABILITIES.OpenGL41) {
+			return GlslVersion.V410;
+		} else if (CAPABILITIES.OpenGL40) {
+			return GlslVersion.V400;
+		} else if (CAPABILITIES.OpenGL33) {
+			return GlslVersion.V330;
+		} else {
+			return GlslVersion.V150;
+		}
+	}
+
+	private static boolean isInstancingSupported() {
+		if (!CAPABILITIES.OpenGL33) {
+			return false;
+		}
+		return true;
+	}
+
+	private static boolean isIndirectSupported() {
+		// The GL requirement cannot be lower because GL_ARB_compute_shader requires at least GL 4.2.
+		if (!CAPABILITIES.OpenGL42) {
+			return false;
+		}
+		if (CAPABILITIES.OpenGL46) {
+			return true;
+		}
+		return CAPABILITIES.GL_ARB_compute_shader
+				&& CAPABILITIES.GL_ARB_direct_state_access
+				&& CAPABILITIES.GL_ARB_multi_bind
+				&& CAPABILITIES.GL_ARB_multi_draw_indirect
+				&& CAPABILITIES.GL_ARB_shader_draw_parameters
+				&& CAPABILITIES.GL_ARB_shader_storage_buffer_object;
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/glsl/GlslVersion.java

@@ -26,5 +26,4 @@ public enum GlslVersion {
 	public String toString() {
 		return Integer.toString(version);
 	}
-
 }

src/main/java/com/jozufozu/flywheel/backend/mixin/RenderSystemMixin.java

@@ -6,10 +6,16 @@ import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
 import com.jozufozu.flywheel.backend.engine.uniform.Uniforms;
+import com.jozufozu.flywheel.backend.gl.GlCompat;
 import com.mojang.blaze3d.systems.RenderSystem;
 
 @Mixin(RenderSystem.class)
 abstract class RenderSystemMixin {
+	@Inject(method = "initRenderer(IZ)V", at = @At("RETURN"))
+	private static void flywheel$onInitRenderer(CallbackInfo ci) {
+		GlCompat.init();
+	}
+
 	@Inject(method = "setShaderFogStart(F)V", at = @At("RETURN"))
 	private static void flywheel$onSetFogStart(CallbackInfo ci) {
 		Uniforms.onFogUpdate();

src/main/resources/assets/flywheel/flywheel/internal/indirect/main.vert

@@ -16,7 +16,11 @@ uniform uint _flw_baseDraw;
 flat out uvec3 _flw_packedMaterial;
 
 void main() {
+#if __VERSION__ < 460
+    uint drawIndex = gl_DrawIDARB + _flw_baseDraw;
+#else
     uint drawIndex = gl_DrawID + _flw_baseDraw;
+#endif
     MeshDrawCommand draw = _flw_drawCommands[drawIndex];
 
     _flw_uberMaterialVertexIndex = draw.materialVertexIndex;
@@ -24,7 +28,11 @@ void main() {
     _flw_unpackMaterialProperties(packedMaterialProperties, flw_material);
     _flw_packedMaterial = uvec3(draw.materialFragmentIndex, draw.packedFogAndCutout, packedMaterialProperties);
 
+#if __VERSION__ < 460
+    uint instanceIndex = _flw_instanceIndices[gl_BaseInstanceARB + gl_InstanceID];
+#else
     uint instanceIndex = _flw_instanceIndices[gl_BaseInstance + gl_InstanceID];
+#endif
     FlwInstance instance = _flw_unpackInstance(instanceIndex);
 
     _flw_main(instance, instanceIndex);