A fine solution

- Rely on transform matrix for all font vertex position stuffs
- Use a skew matrix for italics

common/src/lib/java/dev/engine_room/flywheel/lib/instance/GlyphInstance.java

@@ -9,6 +9,10 @@ import net.minecraft.client.gui.font.glyphs.BakedGlyph;
 import net.minecraft.util.FastColor;
 
 public class GlyphInstance extends AbstractInstance {
+	// Skew x by 1 - 0.25 * y
+	// Note that columns are written as rows.
+	private static final Matrix4f ITALIC_SKEW = new Matrix4f(1, 0, 0, 0, -0.25f, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1);
+
 	public final Matrix4f pose = new Matrix4f();
 
 	public float u0;
@@ -16,14 +20,6 @@ public class GlyphInstance extends AbstractInstance {
 	public float v0;
 	public float v1;
 
-	public float x0;
-	public float x1;
-	public float x2;
-	public float x3;
-
-	public float y0;
-	public float y1;
-
 	public byte red = (byte) 0xFF;
 	public byte green = (byte) 0xFF;
 	public byte blue = (byte) 0xFF;
@@ -47,22 +43,26 @@ public class GlyphInstance extends AbstractInstance {
 		float up = glyphReader.flywheel$up();
 		float down = glyphReader.flywheel$down();
 
-		float f = x + left;
-		float g = x + right;
-		float h = up - 3.0f;
-		float j = down - 3.0f;
-		float k = y + h;
-		float l = y + j;
-		float m = italic ? 1.0f - 0.25f * h : 0.0f;
-		float n = italic ? 1.0f - 0.25f * j : 0.0f;
+		pose.translate(x + left, y + up - 3.0f, 0.0f);
+		pose.scale(right - left, down - up, 1.0f);
 
-		y0 = k;
-		y1 = l;
+		if (italic) {
+			pose.mul(ITALIC_SKEW);
+		}
 
-		x0 = f + m;
-		x1 = f + n;
-		x2 = g + n;
-		x3 = g + m;
+		return this;
+	}
+
+	public GlyphInstance setEffect(BakedGlyph glyph, float x0, float y0, float x1, float y1, float depth) {
+		var glyphReader = FlwLibLink.INSTANCE.getGlyphExtension(glyph);
+
+		u0 = glyphReader.flywheel$u0();
+		u1 = glyphReader.flywheel$u1();
+		v0 = glyphReader.flywheel$v0();
+		v1 = glyphReader.flywheel$v1();
+
+		pose.translate(x0, y0, depth);
+		pose.scale(x1 - x0, y1 - y0, 1.0f);
 
 		return this;
 	}

common/src/lib/java/dev/engine_room/flywheel/lib/instance/InstanceTypes.java

@@ -107,8 +107,6 @@ public final class InstanceTypes {
 			.layout(LayoutBuilder.create()
 					.matrix("pose", FloatRepr.FLOAT, 4)
 					.vector("u0u1v0v1", FloatRepr.FLOAT, 4)
-					.vector("x", FloatRepr.FLOAT, 4)
-					.vector("y", FloatRepr.FLOAT, 2)
 					.vector("color", FloatRepr.UNSIGNED_BYTE, 4)
 					.vector("light", FloatRepr.UNSIGNED_SHORT, 2)
 					.build())
@@ -118,17 +116,11 @@ public final class InstanceTypes {
 				MemoryUtil.memPutFloat(ptr + 68, instance.u1);
 				MemoryUtil.memPutFloat(ptr + 72, instance.v0);
 				MemoryUtil.memPutFloat(ptr + 76, instance.v1);
-				MemoryUtil.memPutFloat(ptr + 80, instance.x0);
-				MemoryUtil.memPutFloat(ptr + 84, instance.x1);
-				MemoryUtil.memPutFloat(ptr + 88, instance.x2);
-				MemoryUtil.memPutFloat(ptr + 92, instance.x3);
-				MemoryUtil.memPutFloat(ptr + 96, instance.y0);
-				MemoryUtil.memPutFloat(ptr + 100, instance.y1);
-				MemoryUtil.memPutByte(ptr + 104, instance.red);
-				MemoryUtil.memPutByte(ptr + 105, instance.green);
-				MemoryUtil.memPutByte(ptr + 106, instance.blue);
-				MemoryUtil.memPutByte(ptr + 107, instance.alpha);
-				ExtraMemoryOps.put2x16(ptr + 108, instance.light);
+				MemoryUtil.memPutByte(ptr + 80, instance.red);
+				MemoryUtil.memPutByte(ptr + 81, instance.green);
+				MemoryUtil.memPutByte(ptr + 82, instance.blue);
+				MemoryUtil.memPutByte(ptr + 83, instance.alpha);
+				ExtraMemoryOps.put2x16(ptr + 84, instance.light);
 			})
 			.vertexShader(Flywheel.rl("instance/glyph.vert"))
 			.cullShader(Flywheel.rl("instance/cull/glyph.glsl"))

common/src/lib/java/dev/engine_room/flywheel/lib/visual/TextVisual.java

@@ -39,6 +39,8 @@ import net.minecraft.util.FormattedCharSink;
  * A visual that renders a single line of text.
  */
 public class TextVisual {
+	public static final float ONE_PIXEL = 0.125f;
+
 	public boolean dropShadow;
 	public boolean with8xOutline;
 	public int backgroundColor = 0;
@@ -120,9 +122,9 @@ public class TextVisual {
 
 				GlyphInstance glyph = recycler.get(new GlyphModelKey(glyphExtension.flywheel$texture(), new GlyphSettings(bold, dropShadow, with8xOutline)));
 
+				glyph.pose.set(pose);
 				glyph.setGlyph(bakedGlyph, this.x, this.y, style.isItalic());
 				glyph.color(r, g, b, this.a);
-				glyph.pose.set(pose);
 				glyph.light = light;
 				glyph.setChanged();
 			}
@@ -146,20 +148,9 @@ public class TextVisual {
 
 			GlyphInstance glyph = recycler.get(new GlyphModelKey(glyphExtension.flywheel$texture(), new GlyphSettings(false, dropShadow, with8xOutline)));
 
-			glyph.u0 = glyphExtension.flywheel$u0();
-			glyph.u1 = glyphExtension.flywheel$u1();
-			glyph.v0 = glyphExtension.flywheel$v0();
-			glyph.v1 = glyphExtension.flywheel$v1();
-
-			glyph.y0 = y0;
-			glyph.y1 = y1;
-
-			glyph.x0 = x0;
-			glyph.x1 = x1;
-			glyph.x2 = x1;
-			glyph.x3 = x0;
-			glyph.color(r, g, b, this.a);
 			glyph.pose.set(pose);
+			glyph.setEffect(bakedGlyph, x0, y0, x1, y1, depth);
+			glyph.color(r, g, b, this.a);
 			glyph.light = light;
 			glyph.setChanged();
 		}
@@ -181,7 +172,6 @@ public class TextVisual {
 
 	private static final Material GLYPH_MATERIAL = SimpleMaterial.builder()
 			.cutout(CutoutShaders.ONE_TENTH)
-			.backfaceCulling(false)
 			.build();
 
 	private record GlyphModelKey(ResourceLocation font, GlyphSettings settings) {
@@ -207,7 +197,7 @@ public class TextVisual {
 							continue;
 						}
 
-						out.add(new Vector3f(x, y, 0));
+						out.add(new Vector3f(x * ONE_PIXEL, y * ONE_PIXEL, 0));
 					}
 				}
 			} else {
@@ -215,11 +205,11 @@ public class TextVisual {
 			}
 
 			if (bold) {
-				out.add(new Vector3f(1, 0, 0));
+				out.add(new Vector3f(ONE_PIXEL, 0, 0));
 			}
 
 			if (dropShadow) {
-				out.add(new Vector3f(1, 1, 0));
+				out.add(new Vector3f(ONE_PIXEL, ONE_PIXEL, 0));
 			}
 
 			return new GlyphMesh(out.toArray(new Vector3f[0]));
@@ -232,6 +222,8 @@ public class TextVisual {
 	 * @param quads Each quad will be expanded into 4 vertices.
 	 */
 	private record GlyphMesh(Vector3f[] quads) implements QuadMesh {
+		private static final float[] X = new float[]{0, 0, 1, 1};
+		private static final float[] Y = new float[]{0, 1, 1, 0};
 
 		@Override
 		public int vertexCount() {
@@ -245,8 +237,8 @@ public class TextVisual {
 				var quadStart = i * 4;
 
 				for (int j = 0; j < 4; j++) {
-					vertexList.x(quadStart + j, quad.x);
-					vertexList.y(quadStart + j, quad.y);
+					vertexList.x(quadStart + j, quad.x + X[j]);
+					vertexList.y(quadStart + j, quad.y + Y[j]);
 					vertexList.z(quadStart + j, quad.z);
 					vertexList.normalX(quadStart + j, 0);
 					vertexList.normalY(quadStart + j, 0);

common/src/lib/resources/assets/flywheel/flywheel/instance/cull/glyph.glsl

@@ -1,9 +1,5 @@
 #include "flywheel:util/matrix.glsl"
 
 void flw_transformBoundingSphere(in FlwInstance i, inout vec3 center, inout float radius) {
-
-    radius += abs(i.x[2] - i.x[0]) + abs(i.y[1] - i.y[0]);
-    center += vec3((i.x[0] + i.x[2]) * 0.5, (i.y[0] + i.y[1]) * 0.5, 0.);
-
     transformBoundingSphere(i.pose, center, radius);
 }

common/src/lib/resources/assets/flywheel/flywheel/instance/glyph.vert

@@ -3,9 +3,6 @@ void flw_instanceVertex(in FlwInstance i) {
 
     uint yIndex = ((vertexInGlyph + 1u) >> 1u) & 1u;
 
-    flw_vertexPos.x += i.x[vertexInGlyph];
-    flw_vertexPos.y += i.y[yIndex];
-
     flw_vertexPos = i.pose * flw_vertexPos;
 
     flw_vertexTexCoord.s = i.u0u1v0v1[(vertexInGlyph & 2u) >> 1u];