Use old mojang rotation math

#24

Author: roro1506HD

src/main/java/btw/lowercase/skyboxify/skybox/SkyboxSkyRenderer.java

@@ -32,9 +32,7 @@
 import net.minecraft.client.multiplayer.ClientLevel;
 import net.minecraft.util.Mth;
 import net.minecraft.world.level.Level;
-import org.joml.AxisAngle4f;
 import org.joml.Matrix4f;
-import org.joml.Quaternionf;
 import org.joml.Vector4f;
 
 public final class SkyboxSkyRenderer {
@@ -133,8 +131,7 @@ private void renderSkyLayer(final SkyLayer skyLayer, final Matrix4f modelViewMat
         final float finalAlpha = Mth.clamp(conditionAlpha * weatherAlpha * fadeAlpha, 0.0F, 1.0F);
         if (!(finalAlpha < 1.0E-4F)) {
             if (skyLayer.rotate()) {
-                // NOTE: Using `mulPose` directly gives a different result.
-				modelViewMatrix.rotate(new Quaternionf(new AxisAngle4f(this.getAngle(level, skyAngle, skyLayer.speed()), skyLayer.axis())));
+                CommonUtils.mulPose(modelViewMatrix, this.getAngle(level, skyAngle, skyLayer.speed()), skyLayer.axis());
             }
 
             //? <=1.21.4 {

src/main/java/btw/lowercase/skyboxify/utils/CommonUtils.java

@@ -27,6 +27,8 @@
 import btw.lowercase.skyboxify.skybox.components.Weather;
 import lombok.experimental.UtilityClass;
 import net.minecraft.util.Mth;
+import org.joml.Matrix4f;
+import org.joml.Vector3fc;
 
 import java.util.List;
 
@@ -109,4 +111,50 @@ public static float getWeatherAlpha(List<Weather> weatherConditions, float rainS
 
 		return Mth.clamp(weatherAlpha, 0.0F, 1.0F);
 	}
+
+    // This method replicates the old Mojang-made Quaternion mulPose method, which was
+    // used for the initial sky transformations which did not have any bobbing issues.
+    // See https://github.com/sp614x/optifine/issues/7235#issuecomment-1581930719
+    public static void mulPose(Matrix4f pose, float angle, Vector3fc axis) {
+        // Quaternion fields
+        float q_sin = Mth.sin(angle * 0.5F);
+        float q_x = axis.x() * q_sin;
+        float q_y = axis.y() * q_sin;
+        float q_z = axis.z() * q_sin;
+        float q_w = Mth.cos(angle * 0.5F);
+
+        // Matrix4f/Matrix3f fields
+        float m_xFactor = 2.0F * q_x * q_x;
+        float m_yFactor = 2.0F * q_y * q_y;
+        float m_zFactor = 2.0F * q_z * q_z;
+        float m_xy = q_x * q_y;
+        float m_yz = q_y * q_z;
+        float m_zx = q_z * q_x;
+        float m_xw = q_x * q_w;
+        float m_yw = q_y * q_w;
+        float m_zw = q_z * q_w;
+        float m_m00 = 1.0F - m_yFactor - m_zFactor;
+        float m_m01 = 2.0F * (m_xy - m_zw);
+        float m_m02 = 2.0F * (m_zx + m_yw);
+        float m_m10 = 2.0F * (m_xy + m_zw);
+        float m_m11 = 1.0F - m_zFactor - m_xFactor;
+        float m_m12 = 2.0F * (m_yz - m_xw);
+        float m_m20 = 2.0F * (m_zx - m_yw);
+        float m_m21 = 2.0F * (m_yz + m_xw);
+        float m_m22 = 1.0F - m_xFactor - m_yFactor;
+
+        // Multiply pose matrix
+        pose.m00(m_m00 * pose.m00() + m_m01 * pose.m10() + m_m02 * pose.m20());
+        pose.m01(m_m00 * pose.m01() + m_m01 * pose.m11() + m_m02 * pose.m21());
+        pose.m02(m_m00 * pose.m02() + m_m01 * pose.m12() + m_m02 * pose.m22());
+        pose.m03(m_m00 * pose.m03() + m_m01 * pose.m13() + m_m02 * pose.m23());
+        pose.m10(m_m10 * pose.m00() + m_m11 * pose.m10() + m_m12 * pose.m20());
+        pose.m11(m_m10 * pose.m01() + m_m11 * pose.m11() + m_m12 * pose.m21());
+        pose.m12(m_m10 * pose.m02() + m_m11 * pose.m12() + m_m12 * pose.m22());
+        pose.m13(m_m10 * pose.m03() + m_m11 * pose.m13() + m_m12 * pose.m23());
+        pose.m20(m_m20 * pose.m00() + m_m21 * pose.m10() + m_m22 * pose.m20());
+        pose.m21(m_m20 * pose.m01() + m_m21 * pose.m11() + m_m22 * pose.m21());
+        pose.m22(m_m20 * pose.m02() + m_m21 * pose.m12() + m_m22 * pose.m22());
+        pose.m23(m_m20 * pose.m03() + m_m21 * pose.m13() + m_m22 * pose.m23());
+    }
 }