Lines aren't too bad

- Add LineModelBuilder and use that instead of the manual mesh creation
  in HitboxComponent.
- Clone mojang's line shader, adapted as a flywheel material.
  - Do not scale the view.
  - Set flw_vertexPos by multiplying by the inverse view projection.
- Remove centerline material.
- Use #define make padded vec3 uniforms available as actual vec3s.
- Add flw_viewProjectionInverse to uniforms.
- Minecarts actually delete the stuff from SimpleEntityVisual.

src/main/java/com/jozufozu/flywheel/backend/engine/uniform/FrameUniforms.java

@@ -1,5 +1,6 @@
 package com.jozufozu.flywheel.backend.engine.uniform;
 
+import org.jetbrains.annotations.Nullable;
 import org.joml.Matrix4f;
 import org.lwjgl.system.MemoryUtil;
 
@@ -7,16 +8,19 @@ import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.api.visualization.VisualizationManager;
 import com.jozufozu.flywheel.lib.math.MatrixMath;
 
+import net.minecraft.client.Camera;
 import net.minecraft.client.Minecraft;
 import net.minecraft.core.Vec3i;
 import net.minecraft.world.phys.Vec3;
 
 public class FrameUniforms implements UniformProvider {
-	public static final int SIZE = 232;
+	public static final int SIZE = 304;
 
+	@Nullable
 	private RenderContext context;
 
 	private final Matrix4f viewProjection = new Matrix4f();
+	private final Matrix4f viewProjectionInverse = new Matrix4f();
 
 	public int byteSize() {
 		return SIZE;
@@ -28,6 +32,10 @@ public class FrameUniforms implements UniformProvider {
 
 	@Override
 	public void write(long ptr) {
+		if (context == null) {
+			return;
+		}
+
 		Vec3i renderOrigin = VisualizationManager.getOrThrow(context.level())
 				.getRenderOrigin();
 		var camera = context.camera();
@@ -45,27 +53,43 @@ public class FrameUniforms implements UniformProvider {
 			Uniforms.frustumCapture = false;
 		}
 
-		MatrixMath.writeUnsafe(viewProjection, ptr + 96);
+		ptr += 96;
-		writeVec3(ptr + 160, camX, camY, camZ);
 
-		var lookVector = camera.getLookVector();
+		ptr = writeMatrices(ptr);
-		writeVec3(ptr + 176, lookVector.x, lookVector.y, lookVector.z);
+
+		ptr = writeCamera(ptr, camX, camY, camZ, camera);
 
-		writeVec2(ptr + 192, camera.getXRot(), camera.getYRot());
 		var window = Minecraft.getInstance()
 				.getWindow();
-
+		ptr = writeVec2(ptr, window.getWidth(), window.getHeight());
-		writeVec2(ptr + 200, window.getWidth(), window.getHeight());
 
 		// default line width: net.minecraft.client.renderer.RenderStateShard.LineStateShard
-		MemoryUtil.memPutFloat(ptr + 208, Math.max(2.5F, (float) window.getWidth() / 1920.0F * 2.5F));
+		MemoryUtil.memPutFloat(ptr, Math.max(2.5F, (float) window.getWidth() / 1920.0F * 2.5F));
+		ptr += 4;
 
-		MemoryUtil.memPutInt(ptr + 212, getConstantAmbientLightFlag(context));
+		MemoryUtil.memPutInt(ptr, getConstantAmbientLightFlag(context));
+		ptr += 4;
 
-		writeTime(ptr + 216);
+		writeTime(ptr);
 	}
 
-	private void writeTime(long ptr) {
+	private long writeMatrices(long ptr) {
+		MatrixMath.writeUnsafe(viewProjection, ptr);
+		MatrixMath.writeUnsafe(viewProjection.invert(viewProjectionInverse), ptr + 64);
+		return ptr + 128;
+	}
+
+	private static long writeCamera(long ptr, float camX, float camY, float camZ, Camera camera) {
+		ptr = writeVec3(ptr, camX, camY, camZ);
+
+		var lookVector = camera.getLookVector();
+		ptr = writeVec3(ptr, lookVector.x, lookVector.y, lookVector.z);
+
+		ptr = writeVec2(ptr, camera.getXRot(), camera.getYRot());
+		return ptr;
+	}
+
+	private long writeTime(long ptr) {
 		int ticks = context.renderer()
 				.getTicks();
 		float partialTick = context.partialTick();
@@ -76,18 +100,21 @@ public class FrameUniforms implements UniformProvider {
 		MemoryUtil.memPutFloat(ptr + 4, partialTick);
 		MemoryUtil.memPutFloat(ptr + 8, renderTicks);
 		MemoryUtil.memPutFloat(ptr + 12, renderSeconds);
+		return ptr + 16;
 	}
 
-	private static void writeVec3(long ptr, float camX, float camY, float camZ) {
+	private static long writeVec3(long ptr, float camX, float camY, float camZ) {
 		MemoryUtil.memPutFloat(ptr, camX);
 		MemoryUtil.memPutFloat(ptr + 4, camY);
 		MemoryUtil.memPutFloat(ptr + 8, camZ);
 		MemoryUtil.memPutFloat(ptr + 12, 0f); // empty component of vec4 because we don't trust std140
+		return ptr + 16;
 	}
 
-	private static void writeVec2(long ptr, float camX, float camY) {
+	private static long writeVec2(long ptr, float camX, float camY) {
 		MemoryUtil.memPutFloat(ptr, camX);
 		MemoryUtil.memPutFloat(ptr + 4, camY);
+		return ptr + 8;
 	}
 
 	private static int getConstantAmbientLightFlag(RenderContext context) {

src/main/java/com/jozufozu/flywheel/lib/material/StandardMaterialShaders.java

@@ -12,7 +12,7 @@ public final class StandardMaterialShaders {
 
 	public static final MaterialShaders WIREFRAME = MaterialShaders.REGISTRY.registerAndGet(new SimpleMaterialShaders(Flywheel.rl("material/wireframe.vert"), Flywheel.rl("material/wireframe.frag")));
 
-	public static final MaterialShaders CENTERLINE = MaterialShaders.REGISTRY.registerAndGet(new SimpleMaterialShaders(Flywheel.rl("material/centerline.vert"), Flywheel.rl("material/centerline.frag")));
+	public static final MaterialShaders LINE = MaterialShaders.REGISTRY.registerAndGet(new SimpleMaterialShaders(Flywheel.rl("material/lines.vert"), Flywheel.rl("material/lines.frag")));
 
 	private StandardMaterialShaders() {
 	}

src/main/java/com/jozufozu/flywheel/lib/model/LineModelBuilder.java

@@ -0,0 +1,159 @@
+package com.jozufozu.flywheel.lib.model;
+
+import org.joml.Vector4f;
+import org.joml.Vector4fc;
+import org.lwjgl.system.MemoryUtil;
+
+import com.jozufozu.flywheel.api.material.Material;
+import com.jozufozu.flywheel.api.model.IndexSequence;
+import com.jozufozu.flywheel.api.model.Mesh;
+import com.jozufozu.flywheel.api.model.Model;
+import com.jozufozu.flywheel.api.vertex.MutableVertexList;
+import com.jozufozu.flywheel.api.vertex.VertexView;
+import com.jozufozu.flywheel.lib.material.SimpleMaterial;
+import com.jozufozu.flywheel.lib.material.StandardMaterialShaders;
+import com.jozufozu.flywheel.lib.memory.MemoryBlock;
+import com.jozufozu.flywheel.lib.vertex.FullVertexView;
+
+import net.minecraft.client.renderer.LightTexture;
+
+public class LineModelBuilder {
+	public static final Material MATERIAL = SimpleMaterial.builder()
+			.shaders(StandardMaterialShaders.LINE)
+			.backfaceCulling(false)
+			.diffuse(false)
+			.build();
+
+	private final VertexView vertices;
+	private MemoryBlock block;
+	private int vertexCount = 0;
+
+	private LineModelBuilder(int segmentCount) {
+		this.vertices = new FullVertexView();
+		this.block = MemoryBlock.malloc(segmentCount * 4 * FullVertexView.STRIDE);
+		vertices.ptr(block.ptr());
+	}
+
+	public static LineModelBuilder withCapacity(int segmentCount) {
+		return new LineModelBuilder(segmentCount);
+	}
+
+	public LineModelBuilder line(float x1, float y1, float z1, float x2, float y2, float z2) {
+		ensureCapacity(vertexCount + 4);
+
+		// We'll use the normal to figure out the orientation of the line in the vertex shader.
+		float dx = x2 - x1;
+		float dy = y2 - y1;
+		float dz = z2 - z1;
+		float length = (float) Math.sqrt(dx * dx + dy * dy + dz * dz);
+		float normalX = dx / length;
+		float normalY = dy / length;
+		float normalZ = dz / length;
+
+		for (int i = 0; i < 2; i++) {
+			vertices.x(vertexCount + i, x1);
+			vertices.y(vertexCount + i, y1);
+			vertices.z(vertexCount + i, z1);
+
+			vertices.x(vertexCount + 2 + i, x2);
+			vertices.y(vertexCount + 2 + i, y2);
+			vertices.z(vertexCount + 2 + i, z2);
+		}
+
+		for (int i = 0; i < 4; i++) {
+			vertices.r(vertexCount + i, 1);
+			vertices.g(vertexCount + i, 1);
+			vertices.b(vertexCount + i, 1);
+			vertices.a(vertexCount + i, 1);
+			vertices.u(vertexCount + i, 0);
+			vertices.v(vertexCount + i, 0);
+			vertices.light(vertexCount + i, LightTexture.FULL_BRIGHT);
+			vertices.normalX(vertexCount + i, normalX);
+			vertices.normalY(vertexCount + i, normalY);
+			vertices.normalZ(vertexCount + i, normalZ);
+		}
+
+		vertexCount += 4;
+
+		return this;
+	}
+
+	public Model build() {
+		vertices.vertexCount(vertexCount);
+
+		var boundingSphere = ModelUtil.computeBoundingSphere(vertices);
+		boundingSphere.w += 0.1f; // make the bounding sphere a little bigger to account for line width
+
+		var mesh = new LineMesh(vertexCount, vertices, block, boundingSphere);
+
+		return new SingleMeshModel(mesh, MATERIAL);
+	}
+
+	private void ensureCapacity(int vertexCount) {
+		if (vertexCount * FullVertexView.STRIDE > block.size()) {
+			this.block = block.realloc(vertexCount * FullVertexView.STRIDE);
+			vertices.ptr(block.ptr());
+		}
+	}
+
+	public static class LineMesh implements Mesh {
+		public static final IndexSequence INDEX_SEQUENCE = (ptr, count) -> {
+			int numVertices = 4 * (count / 6);
+			int baseVertex = 0;
+			while (baseVertex < numVertices) {
+				// triangle a
+				MemoryUtil.memPutInt(ptr, baseVertex);
+				MemoryUtil.memPutInt(ptr + 4, baseVertex + 1);
+				MemoryUtil.memPutInt(ptr + 8, baseVertex + 2);
+				// triangle b
+				MemoryUtil.memPutInt(ptr + 12, baseVertex + 3);
+				MemoryUtil.memPutInt(ptr + 16, baseVertex + 2);
+				MemoryUtil.memPutInt(ptr + 20, baseVertex + 1);
+
+				baseVertex += 4;
+				ptr += 24;
+			}
+		};
+		private final int vertexCount;
+		private final VertexView vertexView;
+		private final MemoryBlock data;
+		private final Vector4f boundingSphere;
+
+		public LineMesh(int vertexCount, VertexView vertexView, MemoryBlock data, Vector4f boundingSphere) {
+			this.vertexCount = vertexCount;
+			this.vertexView = vertexView;
+			this.data = data;
+			this.boundingSphere = boundingSphere;
+		}
+
+		@Override
+		public int vertexCount() {
+			return vertexCount;
+		}
+
+		@Override
+		public void write(MutableVertexList vertexList) {
+			vertexView.writeAll(vertexList);
+		}
+
+		@Override
+		public IndexSequence indexSequence() {
+			return INDEX_SEQUENCE;
+		}
+
+		@Override
+		public int indexCount() {
+			return vertexCount / 2 * 3;
+		}
+
+		@Override
+		public Vector4fc boundingSphere() {
+			return boundingSphere;
+		}
+
+		@Override
+		public void delete() {
+			data.free();
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/visual/components/BoundingBoxComponent.java

@@ -1,195 +0,0 @@
-package com.jozufozu.flywheel.lib.visual.components;
-
-import org.joml.Quaternionf;
-import org.joml.Vector4f;
-import org.joml.Vector4fc;
-
-import com.jozufozu.flywheel.api.material.Material;
-import com.jozufozu.flywheel.api.model.Model;
-import com.jozufozu.flywheel.api.vertex.MutableVertexList;
-import com.jozufozu.flywheel.api.visual.VisualFrameContext;
-import com.jozufozu.flywheel.api.visualization.VisualizationContext;
-import com.jozufozu.flywheel.lib.instance.InstanceTypes;
-import com.jozufozu.flywheel.lib.instance.TransformedInstance;
-import com.jozufozu.flywheel.lib.material.SimpleMaterial;
-import com.jozufozu.flywheel.lib.material.StandardMaterialShaders;
-import com.jozufozu.flywheel.lib.math.MoreMath;
-import com.jozufozu.flywheel.lib.model.QuadMesh;
-import com.jozufozu.flywheel.lib.model.SingleMeshModel;
-import com.jozufozu.flywheel.lib.visual.EntityComponent;
-import com.jozufozu.flywheel.lib.visual.SmartRecycler;
-
-import net.minecraft.client.Minecraft;
-import net.minecraft.client.renderer.LightTexture;
-import net.minecraft.util.Mth;
-import net.minecraft.world.entity.Entity;
-import net.minecraft.world.entity.LivingEntity;
-
-public class BoundingBoxComponent implements EntityComponent {
-	private static final Material WIREFRAME = SimpleMaterial.builder()
-			.shaders(StandardMaterialShaders.WIREFRAME)
-			.backfaceCulling(false)
-			.build();
-
-	private static final Material CENTERLINE = SimpleMaterial.builder()
-			.shaders(StandardMaterialShaders.CENTERLINE)
-			.backfaceCulling(false)
-			.build();
-	private static final Model BOX = new SingleMeshModel(BoundingBoxMesh.INSTANCE, WIREFRAME);
-
-	// Should we try a single quad oriented to face the camera instead?
-	private static final Model LINE = new SingleMeshModel(BoundingBoxMesh.INSTANCE, CENTERLINE);
-
-	private final VisualizationContext context;
-	private final Entity entity;
-
-	private boolean showEyeBox;
-
-	private final SmartRecycler<Model, TransformedInstance> recycler;
-
-	public BoundingBoxComponent(VisualizationContext context, Entity entity) {
-		this.context = context;
-		this.entity = entity;
-		this.showEyeBox = entity instanceof LivingEntity;
-
-		this.recycler = new SmartRecycler<>(this::createInstance);
-	}
-
-	private TransformedInstance createInstance(Model model) {
-		TransformedInstance instance = context.instancerProvider()
-				.instancer(InstanceTypes.TRANSFORMED, model)
-				.createInstance();
-		instance.setBlockLight(LightTexture.block(LightTexture.FULL_BLOCK));
-		instance.setChanged();
-		return instance;
-	}
-
-	public BoundingBoxComponent showEyeBox(boolean renderEyeBox) {
-		this.showEyeBox = renderEyeBox;
-		return this;
-	}
-
-	@Override
-	public void beginFrame(VisualFrameContext context) {
-		recycler.resetCount();
-
-		var shouldRenderHitBoxes = Minecraft.getInstance()
-				.getEntityRenderDispatcher()
-				.shouldRenderHitBoxes();
-		if (shouldRenderHitBoxes && !entity.isInvisible() && !Minecraft.getInstance()
-				.showOnlyReducedInfo()) {
-			double entityX = Mth.lerp(context.partialTick(), entity.xOld, entity.getX());
-			double entityY = Mth.lerp(context.partialTick(), entity.yOld, entity.getY());
-			double entityZ = Mth.lerp(context.partialTick(), entity.zOld, entity.getZ());
-
-			var bbWidth = entity.getBbWidth();
-			var bbHeight = entity.getBbHeight();
-			var bbWidthHalf = bbWidth * 0.5;
-			recycler.get(BOX)
-					.loadIdentity()
-					.translate(entityX - bbWidthHalf, entityY, entityZ - bbWidthHalf)
-					.scale(bbWidth, bbHeight, bbWidth)
-					.setChanged();
-
-			// TODO: multipart entities, but forge seems to have an
-			//  injection for them so we'll need platform specific code.
-
-			if (showEyeBox) {
-				recycler.get(BOX)
-						.loadIdentity()
-						.translate(entityX - bbWidthHalf, entityY + entity.getEyeHeight() - 0.01, entityZ - bbWidthHalf)
-						.scale(bbWidth, 0.02f, bbWidth)
-						.setColor(255, 0, 0)
-						.setChanged();
-			}
-
-			var viewVector = entity.getViewVector(context.partialTick());
-
-			recycler.get(LINE)
-					.loadIdentity()
-					.translate(entityX, entityY + entity.getEyeHeight(), entityZ)
-					.rotate(new Quaternionf().rotateTo(0, 1, 0, (float) viewVector.x, (float) viewVector.y, (float) viewVector.z))
-					.scale(0.02f, 2f, 0.02f)
-					.setColor(0, 0, 255)
-					.setChanged();
-		}
-
-		recycler.discardExtra();
-	}
-
-	@Override
-	public void delete() {
-		recycler.delete();
-	}
-
-	private static class BoundingBoxMesh implements QuadMesh {
-		private static final BoundingBoxMesh INSTANCE = new BoundingBoxMesh();
-		private static final Vector4fc BOUNDING_SPHERE = new Vector4f(0.5f, 0.5f, 0.5f, MoreMath.SQRT_3_OVER_2);
-
-		private BoundingBoxMesh() {
-		}
-
-		@Override
-		public int vertexCount() {
-			return 24;
-		}
-
-		@Override
-		public void write(MutableVertexList vertexList) {
-			// very cursed, maybe we should use vanilla ModelParts instead?
-			writeVertex(vertexList, 0, 0, 0, 0, 0, 0);
-			writeVertex(vertexList, 1, 1, 0, 0, 1, 0);
-			writeVertex(vertexList, 2, 1, 1, 0, 1, 1);
-			writeVertex(vertexList, 3, 0, 1, 0, 0, 1);
-
-			writeVertex(vertexList, 4, 0, 0, 1, 0, 0);
-			writeVertex(vertexList, 5, 0, 0, 0, 1, 0);
-			writeVertex(vertexList, 6, 0, 1, 0, 1, 1);
-			writeVertex(vertexList, 7, 0, 1, 1, 0, 1);
-
-			writeVertex(vertexList, 8, 0, 1, 0, 0, 0);
-			writeVertex(vertexList, 9, 1, 1, 0, 1, 0);
-			writeVertex(vertexList, 10, 1, 1, 1, 1, 1);
-			writeVertex(vertexList, 11, 0, 1, 1, 0, 1);
-
-			writeVertex(vertexList, 12, 1, 0, 1, 0, 0);
-			writeVertex(vertexList, 13, 0, 0, 1, 1, 0);
-			writeVertex(vertexList, 14, 0, 1, 1, 1, 1);
-			writeVertex(vertexList, 15, 1, 1, 1, 0, 1);
-
-			writeVertex(vertexList, 16, 1, 0, 0, 0, 0);
-			writeVertex(vertexList, 17, 1, 0, 1, 1, 0);
-			writeVertex(vertexList, 18, 1, 1, 1, 1, 1);
-			writeVertex(vertexList, 19, 1, 1, 0, 0, 1);
-
-			writeVertex(vertexList, 20, 0, 0, 0, 0, 0);
-			writeVertex(vertexList, 21, 1, 0, 0, 1, 0);
-			writeVertex(vertexList, 22, 1, 0, 1, 1, 1);
-			writeVertex(vertexList, 23, 0, 0, 1, 0, 1);
-		}
-
-		@Override
-		public Vector4fc boundingSphere() {
-			return BOUNDING_SPHERE;
-		}
-
-		@Override
-		public void delete() {
-		}
-
-		private static void writeVertex(MutableVertexList vertexList, int i, float x, float y, float z, float u, float v) {
-			vertexList.x(i, x);
-			vertexList.y(i, y);
-			vertexList.z(i, z);
-			vertexList.r(i, 1);
-			vertexList.g(i, 1);
-			vertexList.b(i, 1);
-			vertexList.u(i, u);
-			vertexList.v(i, v);
-			vertexList.light(i, LightTexture.FULL_BRIGHT);
-			vertexList.normalX(i, 0);
-			vertexList.normalY(i, 1);
-			vertexList.normalZ(i, 0);
-		}
-	}
-}

src/main/java/com/jozufozu/flywheel/lib/visual/components/HitboxComponent.java

@@ -0,0 +1,134 @@
+package com.jozufozu.flywheel.lib.visual.components;
+
+import org.joml.Quaternionf;
+
+import com.jozufozu.flywheel.api.model.Model;
+import com.jozufozu.flywheel.api.visual.VisualFrameContext;
+import com.jozufozu.flywheel.api.visualization.VisualizationContext;
+import com.jozufozu.flywheel.lib.instance.InstanceTypes;
+import com.jozufozu.flywheel.lib.instance.TransformedInstance;
+import com.jozufozu.flywheel.lib.model.LineModelBuilder;
+import com.jozufozu.flywheel.lib.model.ModelHolder;
+import com.jozufozu.flywheel.lib.visual.EntityComponent;
+import com.jozufozu.flywheel.lib.visual.SmartRecycler;
+
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.LightTexture;
+import net.minecraft.util.Mth;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.LivingEntity;
+
+public class HitboxComponent implements EntityComponent {
+	//    010------110
+	//    /|       /|
+	//   / |      / |
+	// 011------111 |
+	//  |  |     |  |
+	//  | 000----|-100
+	//  | /      | /
+	//  |/       |/
+	// 001------101
+	private static final ModelHolder BOX = new ModelHolder(() -> LineModelBuilder.withCapacity(12)
+			// Starting from 0, 0, 0
+			.line(0, 0, 0, 0, 0, 1)
+			.line(0, 0, 0, 0, 1, 0)
+			.line(0, 0, 0, 1, 0, 0)
+			// Starting from 0, 1, 1
+			.line(0, 1, 1, 0, 1, 0)
+			.line(0, 1, 1, 0, 0, 1)
+			.line(0, 1, 1, 1, 1, 1)
+			// Starting from 1, 0, 1
+			.line(1, 0, 1, 1, 0, 0)
+			.line(1, 0, 1, 1, 1, 1)
+			.line(1, 0, 1, 0, 0, 1)
+			// Starting from 1, 1, 0
+			.line(1, 1, 0, 1, 1, 1)
+			.line(1, 1, 0, 1, 0, 0)
+			.line(1, 1, 0, 0, 1, 0)
+			.build());
+
+	private static final ModelHolder LINE = new ModelHolder(() -> LineModelBuilder.withCapacity(1)
+			.line(0, 0, 0, 0, 2, 0)
+			.build());
+
+	private final VisualizationContext context;
+	private final Entity entity;
+
+	private boolean showEyeBox;
+
+	private final SmartRecycler<Model, TransformedInstance> recycler;
+
+	public HitboxComponent(VisualizationContext context, Entity entity) {
+		this.context = context;
+		this.entity = entity;
+		this.showEyeBox = entity instanceof LivingEntity;
+
+		this.recycler = new SmartRecycler<>(this::createInstance);
+	}
+
+	private TransformedInstance createInstance(Model model) {
+		TransformedInstance instance = context.instancerProvider()
+				.instancer(InstanceTypes.TRANSFORMED, model)
+				.createInstance();
+		instance.setBlockLight(LightTexture.block(LightTexture.FULL_BLOCK));
+		instance.setChanged();
+		return instance;
+	}
+
+	public HitboxComponent showEyeBox(boolean renderEyeBox) {
+		this.showEyeBox = renderEyeBox;
+		return this;
+	}
+
+	@Override
+	public void beginFrame(VisualFrameContext context) {
+		recycler.resetCount();
+
+		var shouldRenderHitBoxes = Minecraft.getInstance()
+				.getEntityRenderDispatcher()
+				.shouldRenderHitBoxes();
+		if (shouldRenderHitBoxes && !entity.isInvisible() && !Minecraft.getInstance()
+				.showOnlyReducedInfo()) {
+			double entityX = Mth.lerp(context.partialTick(), entity.xOld, entity.getX());
+			double entityY = Mth.lerp(context.partialTick(), entity.yOld, entity.getY());
+			double entityZ = Mth.lerp(context.partialTick(), entity.zOld, entity.getZ());
+
+			var bbWidth = entity.getBbWidth();
+			var bbHeight = entity.getBbHeight();
+			var bbWidthHalf = bbWidth * 0.5;
+			recycler.get(BOX.get())
+					.loadIdentity()
+					.translate(entityX - bbWidthHalf, entityY, entityZ - bbWidthHalf)
+					.scale(bbWidth, bbHeight, bbWidth)
+					.setChanged();
+
+			// TODO: multipart entities, but forge seems to have an
+			//  injection for them so we'll need platform specific code.
+
+			if (showEyeBox) {
+				recycler.get(BOX.get())
+						.loadIdentity()
+						.translate(entityX - bbWidthHalf, entityY + entity.getEyeHeight() - 0.01, entityZ - bbWidthHalf)
+						.scale(bbWidth, 0.02f, bbWidth)
+						.setColor(255, 0, 0)
+						.setChanged();
+			}
+
+			var viewVector = entity.getViewVector(context.partialTick());
+
+			recycler.get(LINE.get())
+					.loadIdentity()
+					.translate(entityX, entityY + entity.getEyeHeight(), entityZ)
+					.rotate(new Quaternionf().rotateTo(0, 1, 0, (float) viewVector.x, (float) viewVector.y, (float) viewVector.z))
+					.setColor(0, 0, 255)
+					.setChanged();
+		}
+
+		recycler.discardExtra();
+	}
+
+	@Override
+	public void delete() {
+		recycler.delete();
+	}
+}

src/main/java/com/jozufozu/flywheel/vanilla/MinecartVisual.java

@@ -15,8 +15,8 @@ import com.jozufozu.flywheel.lib.model.Models;
 import com.jozufozu.flywheel.lib.model.SingleMeshModel;
 import com.jozufozu.flywheel.lib.model.part.ModelPartConverter;
 import com.jozufozu.flywheel.lib.visual.SimpleEntityVisual;
-import com.jozufozu.flywheel.lib.visual.components.BoundingBoxComponent;
 import com.jozufozu.flywheel.lib.visual.components.FireComponent;
+import com.jozufozu.flywheel.lib.visual.components.HitboxComponent;
 import com.jozufozu.flywheel.lib.visual.components.ShadowComponent;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.mojang.math.Axis;
@@ -63,7 +63,7 @@ public class MinecartVisual<T extends AbstractMinecart> extends SimpleEntityVisu
 	public void init(float partialTick) {
 		addComponent(new ShadowComponent(visualizationContext, entity).radius(0.7f));
 		addComponent(new FireComponent(visualizationContext, entity));
-		addComponent(new BoundingBoxComponent(visualizationContext, entity));
+		addComponent(new HitboxComponent(visualizationContext, entity));
 
 		body = createBodyInstance();
 		blockState = entity.getDisplayBlockState();
@@ -210,6 +210,7 @@ public class MinecartVisual<T extends AbstractMinecart> extends SimpleEntityVisu
 
 	@Override
 	protected void _delete() {
+		super._delete();
 		body.delete();
 		if (contents != null) {
 			contents.delete();

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

@@ -9,6 +9,7 @@ void _flw_main(in FlwInstance instance) {
 
     flw_vertexNormal = normalize(flw_vertexNormal);
 
-    flw_distance = fogDistance(flw_vertexPos.xyz, flw_cameraPos.xyz, flw_fogShape);
+    flw_distance = fogDistance(flw_vertexPos.xyz, flw_cameraPos, flw_fogShape);
+
     gl_Position = flw_viewProjection * flw_vertexPos;
 }

src/main/resources/assets/flywheel/flywheel/internal/uniforms/frame.glsl

@@ -11,9 +11,12 @@ struct FrustumPlanes {
 
 layout(std140) uniform _FlwFrameUniforms {
     FrustumPlanes flw_frustumPlanes;
+
     mat4 flw_viewProjection;
-    vec4 flw_cameraPos;
+    mat4 flw_viewProjectionInverse;
-    vec4 flw_cameraLook;
+
+    vec4 _flw_cameraPos;
+    vec4 _flw_cameraLook;
     vec2 flw_cameraRot;
 
     vec2 flw_viewportSize;
@@ -27,3 +30,6 @@ layout(std140) uniform _FlwFrameUniforms {
     float flw_renderTicks;
     float flw_renderSeconds;
 };
+
+#define flw_cameraPos _flw_cameraPos.xyz
+#define flw_cameraLook _flw_cameraLook.xyz

src/main/resources/assets/flywheel/flywheel/material/centerline.frag

@@ -1,10 +0,0 @@
-void flw_materialFragment() {
-    float toCenter = abs(flw_vertexTexCoord.s - 0.5);
-
-    // multiply by fwidth to get the width of the edge in screen space
-    if (flw_defaultLineWidth * fwidth(toCenter) < toCenter) {
-        discard;
-    }
-
-    flw_fragColor = flw_vertexColor;
-}

src/main/resources/assets/flywheel/flywheel/material/centerline.vert

@@ -1,2 +0,0 @@
-void flw_materialVertex() {
-}

src/main/resources/assets/flywheel/flywheel/material/lines.frag

@@ -0,0 +1,3 @@
+void flw_materialFragment() {
+    flw_fragColor = flw_vertexColor;
+}

src/main/resources/assets/flywheel/flywheel/material/lines.vert

@@ -0,0 +1,20 @@
+void flw_materialVertex() {
+    vec4 linePosStart = flw_viewProjection * flw_vertexPos;
+    vec4 linePosEnd = flw_viewProjection * (flw_vertexPos + vec4(flw_vertexNormal, 0.));
+
+    vec3 ndc1 = linePosStart.xyz / linePosStart.w;
+    vec3 ndc2 = linePosEnd.xyz / linePosEnd.w;
+
+    vec2 lineScreenDirection = normalize((ndc2.xy - ndc1.xy) * flw_viewportSize);
+    vec2 lineOffset = vec2(-lineScreenDirection.y, lineScreenDirection.x) * flw_defaultLineWidth / flw_viewportSize;
+
+    if (lineOffset.x < 0.0) {
+        lineOffset *= -1.0;
+    }
+
+    if (gl_VertexID % 2 == 0) {
+        flw_vertexPos = flw_viewProjectionInverse * vec4((ndc1 + vec3(lineOffset, 0.)) * linePosStart.w, linePosStart.w);
+    } else {
+        flw_vertexPos = flw_viewProjectionInverse * vec4((ndc1 - vec3(lineOffset, 0.)) * linePosStart.w, linePosStart.w);
+    }
+}