From 56c0e51e546c28b0616b041bf82eab1db45d4e4f Mon Sep 17 00:00:00 2001
From: Jozufozu <jozsefaug@gmail.com>
Date: Sun, 24 Dec 2023 11:55:33 -0800
Subject: [PATCH] Consecutive normal draws

- Don't use MDI on intel, instead submit multiple draw indirect commands
---
 .../engine/indirect/IndirectCullingGroup.java | 12 +++++++-
 .../java/com/jozufozu/flywheel/gl/Driver.java |  9 ++++++
 .../com/jozufozu/flywheel/gl/GlCompat.java    | 28 ++++++++++++++-----
 3 files changed, 41 insertions(+), 8 deletions(-)
 create mode 100644 src/main/java/com/jozufozu/flywheel/gl/Driver.java

diff --git a/src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectCullingGroup.java b/src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectCullingGroup.java
index b671f2cfc..99609b419 100644
--- a/src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectCullingGroup.java
+++ b/src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectCullingGroup.java
@@ -3,6 +3,7 @@ package com.jozufozu.flywheel.backend.engine.indirect;
 import static org.lwjgl.opengl.GL11.GL_TRIANGLES;
 import static org.lwjgl.opengl.GL11.GL_UNSIGNED_INT;
 import static org.lwjgl.opengl.GL30.glUniform1ui;
+import static org.lwjgl.opengl.GL40.glDrawElementsIndirect;
 import static org.lwjgl.opengl.GL42.GL_COMMAND_BARRIER_BIT;
 import static org.lwjgl.opengl.GL42.glMemoryBarrier;
 import static org.lwjgl.opengl.GL43.GL_SHADER_STORAGE_BARRIER_BIT;
@@ -24,6 +25,7 @@ import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.backend.compile.IndirectPrograms;
 import com.jozufozu.flywheel.backend.engine.MaterialRenderState;
 import com.jozufozu.flywheel.backend.engine.UniformBuffer;
+import com.jozufozu.flywheel.gl.Driver;
 import com.jozufozu.flywheel.gl.GlCompat;
 import com.jozufozu.flywheel.gl.shader.GlProgram;
 import com.jozufozu.flywheel.lib.context.Contexts;
@@ -267,7 +269,15 @@ public class IndirectCullingGroup<I extends Instance> {
 	private record MultiDraw(Material material, int start, int end) {
 		void submit() {
 			MaterialRenderState.setup(material);
-			glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, start * IndirectBuffers.DRAW_COMMAND_STRIDE, end - start, (int) IndirectBuffers.DRAW_COMMAND_STRIDE);
+
+			if (GlCompat.DRIVER == Driver.INTEL) {
+				// Intel renders garbage with MDI, but Consecutive Normal Draws works fine.
+				for (int i = start; i < end; i++) {
+					glDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, i * IndirectBuffers.DRAW_COMMAND_STRIDE);
+				}
+			} else {
+				glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, start * IndirectBuffers.DRAW_COMMAND_STRIDE, end - start, (int) IndirectBuffers.DRAW_COMMAND_STRIDE);
+			}
 		}
 	}
 }
diff --git a/src/main/java/com/jozufozu/flywheel/gl/Driver.java b/src/main/java/com/jozufozu/flywheel/gl/Driver.java
new file mode 100644
index 000000000..54fbc87fe
--- /dev/null
+++ b/src/main/java/com/jozufozu/flywheel/gl/Driver.java
@@ -0,0 +1,9 @@
+package com.jozufozu.flywheel.gl;
+
+public enum Driver {
+	NVIDIA,
+	AMD,
+	INTEL,
+	MESA,
+	UNKNOWN,
+}
diff --git a/src/main/java/com/jozufozu/flywheel/gl/GlCompat.java b/src/main/java/com/jozufozu/flywheel/gl/GlCompat.java
index 4ab492405..6305b4666 100644
--- a/src/main/java/com/jozufozu/flywheel/gl/GlCompat.java
+++ b/src/main/java/com/jozufozu/flywheel/gl/GlCompat.java
@@ -22,17 +22,17 @@ import net.minecraft.Util;
  */
 public final class GlCompat {
 	public static final GLCapabilities CAPABILITIES = GL.createCapabilities();
-	public static final boolean AMD = _decideIfWeAreAMD();
 	public static final boolean WINDOWS = _decideIfWeAreWindows();
 	public static final boolean ALLOW_DSA = true;
 	public static final boolean SUPPORTS_INDIRECT = _decideIfWeSupportIndirect();
 	public static final int SUBGROUP_SIZE = _subgroupSize();
+	public static final Driver DRIVER = _readVendorString();
 
 	private GlCompat() {
 	}
 
 	public static boolean onAMDWindows() {
-		return AMD && WINDOWS;
+		return DRIVER == Driver.AMD && WINDOWS;
 	}
 
 	public static boolean supportsInstancing() {
@@ -43,15 +43,25 @@ public final class GlCompat {
 		return SUPPORTS_INDIRECT;
 	}
 
-	private static boolean _decideIfWeAreAMD() {
+	private static Driver _readVendorString() {
 		String vendor = GL20C.glGetString(GL20C.GL_VENDOR);
 
 		if (vendor == null) {
-			return false;
+			return Driver.UNKNOWN;
 		}
 
 		// vendor string I got was "ATI Technologies Inc."
-		return vendor.contains("ATI") || vendor.contains("AMD");
+		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() {
@@ -66,8 +76,12 @@ public final class GlCompat {
 		if (CAPABILITIES.GL_KHR_shader_subgroup) {
 			return GL31C.glGetInteger(KHRShaderSubgroup.GL_SUBGROUP_SIZE_KHR);
 		}
-		// try to guess
-		return AMD ? 64 : 32;
+		// 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) {