From 4e8dcb02482bb29bb75380a45f486702fd109e63 Mon Sep 17 00:00:00 2001
From: PepperCode1 <44146161+PepperCode1@users.noreply.github.com>
Date: Mon, 15 Jul 2024 16:13:24 -0600
Subject: [PATCH] Move Intel MDI workaround to GlCompat

---
 .../engine/indirect/IndirectCullingGroup.java | 12 +-----------
 .../flywheel/backend/gl/GlCompat.java         | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/common/src/backend/java/dev/engine_room/flywheel/backend/engine/indirect/IndirectCullingGroup.java b/common/src/backend/java/dev/engine_room/flywheel/backend/engine/indirect/IndirectCullingGroup.java
index c4d5fb8ea..f72f66af9 100644
--- a/common/src/backend/java/dev/engine_room/flywheel/backend/engine/indirect/IndirectCullingGroup.java
+++ b/common/src/backend/java/dev/engine_room/flywheel/backend/engine/indirect/IndirectCullingGroup.java
@@ -3,12 +3,10 @@ package dev.engine_room.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;
 import static org.lwjgl.opengl.GL43.glDispatchCompute;
-import static org.lwjgl.opengl.GL43.glMultiDrawElementsIndirect;
 
 import java.util.ArrayList;
 import java.util.Comparator;
@@ -27,7 +25,6 @@ import dev.engine_room.flywheel.backend.engine.MaterialRenderState;
 import dev.engine_room.flywheel.backend.engine.MeshPool;
 import dev.engine_room.flywheel.backend.engine.embed.Environment;
 import dev.engine_room.flywheel.backend.engine.uniform.Uniforms;
-import dev.engine_room.flywheel.backend.gl.Driver;
 import dev.engine_room.flywheel.backend.gl.GlCompat;
 import dev.engine_room.flywheel.backend.gl.shader.GlProgram;
 import dev.engine_room.flywheel.lib.math.MoreMath;
@@ -282,14 +279,7 @@ public class IndirectCullingGroup<I extends Instance> {
 
 	private record MultiDraw(Material material, int start, int end) {
 		private void submit() {
-			if (GlCompat.DRIVER == Driver.INTEL) {
-				// Intel renders garbage with MDI, but Consecutive Normal Draws works fine.
-				for (int i = this.start; i < this.end; i++) {
-					glDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, i * IndirectBuffers.DRAW_COMMAND_STRIDE);
-				}
-			} else {
-				glMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, this.start * IndirectBuffers.DRAW_COMMAND_STRIDE, this.end - this.start, (int) IndirectBuffers.DRAW_COMMAND_STRIDE);
-			}
+			GlCompat.safeMultiDrawElementsIndirect(GL_TRIANGLES, GL_UNSIGNED_INT, this.start * IndirectBuffers.DRAW_COMMAND_STRIDE, this.end - this.start, (int) IndirectBuffers.DRAW_COMMAND_STRIDE);
 		}
 	}
 }
diff --git a/common/src/backend/java/dev/engine_room/flywheel/backend/gl/GlCompat.java b/common/src/backend/java/dev/engine_room/flywheel/backend/gl/GlCompat.java
index d860d2556..b7efa23ed 100644
--- a/common/src/backend/java/dev/engine_room/flywheel/backend/gl/GlCompat.java
+++ b/common/src/backend/java/dev/engine_room/flywheel/backend/gl/GlCompat.java
@@ -8,6 +8,8 @@ import org.lwjgl.opengl.GL;
 import org.lwjgl.opengl.GL20;
 import org.lwjgl.opengl.GL20C;
 import org.lwjgl.opengl.GL31C;
+import org.lwjgl.opengl.GL40;
+import org.lwjgl.opengl.GL43;
 import org.lwjgl.opengl.GLCapabilities;
 import org.lwjgl.opengl.KHRShaderSubgroup;
 import org.lwjgl.system.MemoryStack;
@@ -71,6 +73,23 @@ public final class GlCompat {
 		}
 	}
 
+	/**
+	 * Similar in function to {@link GL43#glMultiDrawElementsIndirect(int, int, long, int, int)},
+	 * but uses consecutive DI instead of MDI if MDI is known to not work well with the current driver.
+	 * Unlike the original function, stride cannot be equal to 0.
+	 */
+	public static void safeMultiDrawElementsIndirect(int mode, int type, long indirect, int drawcount, int stride) {
+		if (GlCompat.DRIVER == Driver.INTEL) {
+			// Intel renders garbage with MDI, but consecutive DI works fine.
+			for (int i = 0; i < drawcount; i++) {
+				GL40.glDrawElementsIndirect(mode, type, indirect);
+				indirect += stride;
+			}
+		} else {
+			GL43.glMultiDrawElementsIndirect(mode, type, indirect, drawcount, stride);
+		}
+	}
+
 	private static Driver readVendorString() {
 		if (CAPABILITIES == null) {
 			return Driver.UNKNOWN;