What a view!

- Add entity view vectors to BoundingBoxComponent.
- Add "centerline" material, similar to wireframe.
- Add SmartRecycler to create recyclers based on a parameter.

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

@@ -12,6 +12,8 @@ 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")));
+
 	private StandardMaterialShaders() {
 	}
 

src/main/java/com/jozufozu/flywheel/lib/visual/SmartRecycler.java

@@ -0,0 +1,37 @@
+package com.jozufozu.flywheel.lib.visual;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+import com.jozufozu.flywheel.api.instance.Instance;
+
+public class SmartRecycler<K, I extends Instance> {
+	private final Function<K, I> factory;
+	private final Map<K, InstanceRecycler<I>> recyclers = new HashMap<>();
+
+	public SmartRecycler(Function<K, I> factory) {
+		this.factory = factory;
+	}
+
+	public void resetCount() {
+		recyclers.values()
+				.forEach(InstanceRecycler::resetCount);
+	}
+
+	public I get(K key) {
+		return recyclers.computeIfAbsent(key, k -> new InstanceRecycler<>(() -> factory.apply(k)))
+				.get();
+	}
+
+	public void discardExtra() {
+		recyclers.values()
+				.forEach(InstanceRecycler::discardExtra);
+	}
+
+	public void delete() {
+		recyclers.values()
+				.forEach(InstanceRecycler::delete);
+		recyclers.clear();
+	}
+}

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

@@ -1,5 +1,6 @@
 package com.jozufozu.flywheel.lib.visual.components;
 
+import org.joml.Quaternionf;
 import org.joml.Vector4f;
 import org.joml.Vector4fc;
 
@@ -16,7 +17,7 @@ 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.InstanceRecycler;
+import com.jozufozu.flywheel.lib.visual.SmartRecycler;
 
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.LightTexture;
@@ -25,30 +26,38 @@ import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.LivingEntity;
 
 public class BoundingBoxComponent implements EntityComponent {
-	private static final Material MATERIAL = SimpleMaterial.builder()
+	private static final Material WIREFRAME = SimpleMaterial.builder()
 			.shaders(StandardMaterialShaders.WIREFRAME)
 			.backfaceCulling(false)
 			.build();
-	private static final Model MODEL = new SingleMeshModel(BoundingBoxMesh.INSTANCE, MATERIAL);
+
+	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 InstanceRecycler<TransformedInstance> recycler;
+	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 InstanceRecycler<>(this::createInstance);
+		this.recycler = new SmartRecycler<>(this::createInstance);
 	}
 
-	private TransformedInstance createInstance() {
+	private TransformedInstance createInstance(Model model) {
 		TransformedInstance instance = context.instancerProvider()
-				.instancer(InstanceTypes.TRANSFORMED, MODEL)
+				.instancer(InstanceTypes.TRANSFORMED, model)
 				.createInstance();
 		instance.setBlockLight(LightTexture.block(LightTexture.FULL_BLOCK));
 		instance.setChanged();
@@ -76,22 +85,33 @@ public class BoundingBoxComponent implements EntityComponent {
 			var bbWidth = entity.getBbWidth();
 			var bbHeight = entity.getBbHeight();
 			var bbWidthHalf = bbWidth * 0.5;
-			recycler.get()
+			recycler.get(BOX)
 					.loadIdentity()
 					.translate(entityX - bbWidthHalf, entityY, entityZ - bbWidthHalf)
 					.scale(bbWidth, bbHeight, bbWidth)
 					.setChanged();
 
-			// TODO: multipart entities and view vectors
+			// TODO: multipart entities, but forge seems to have an
+			//  injection for them so we'll need platform specific code.
 
 			if (showEyeBox) {
-				recycler.get()
+				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();

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

@@ -4,6 +4,7 @@ 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;
@@ -15,7 +16,7 @@ import com.jozufozu.flywheel.lib.model.ModelCache;
 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.InstanceRecycler;
+import com.jozufozu.flywheel.lib.visual.SmartRecycler;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.mojang.math.Axis;
 
@@ -42,20 +43,18 @@ public class FireComponent implements EntityComponent {
 	private final Entity entity;
 	private final PoseStack stack = new PoseStack();
 
-	private final InstanceRecycler<TransformedInstance> fire0;
+	private final SmartRecycler<Model, TransformedInstance> recycler;
-	private final InstanceRecycler<TransformedInstance> fire1;
 
 	public FireComponent(VisualizationContext context, Entity entity) {
 		this.context = context;
 		this.entity = entity;
 
-		fire0 = new InstanceRecycler<>(() -> createInstance(ModelBakery.FIRE_0));
+		recycler = new SmartRecycler<>(this::createInstance);
-		fire1 = new InstanceRecycler<>(() -> createInstance(ModelBakery.FIRE_1));
 	}
 
-	private TransformedInstance createInstance(net.minecraft.client.resources.model.Material texture) {
+	private TransformedInstance createInstance(Model model) {
 		TransformedInstance instance = context.instancerProvider()
-				.instancer(InstanceTypes.TRANSFORMED, FIRE_MODELS.get(texture))
+				.instancer(InstanceTypes.TRANSFORMED, model)
 				.createInstance();
 		instance.setBlockLight(LightTexture.block(LightTexture.FULL_BLOCK));
 		instance.setChanged();
@@ -70,15 +69,13 @@ public class FireComponent implements EntityComponent {
 	 */
 	@Override
 	public void beginFrame(VisualFrameContext context) {
-		fire0.resetCount();
+		recycler.resetCount();
-		fire1.resetCount();
 
 		if (entity.displayFireAnimation()) {
 			setupInstances(context);
 		}
 
-		fire0.discardExtra();
+		recycler.discardExtra();
-		fire1.discardExtra();
 	}
 
 	private void setupInstances(VisualFrameContext context) {
@@ -101,7 +98,7 @@ public class FireComponent implements EntityComponent {
 		stack.translate(0.0F, 0.0F, -0.3F + (float) ((int) maxHeight) * 0.02F);
 
 		for (int i = 0; y < maxHeight; ++i) {
-			var instance = (i % 2 == 0 ? this.fire0 : this.fire1).get()
+			var instance = recycler.get(FIRE_MODELS.get(i % 2 == 0 ? ModelBakery.FIRE_0 : ModelBakery.FIRE_1))
 					.setTransform(stack)
 					.scaleX(width)
 					.translate(0, y, z);
@@ -123,8 +120,7 @@ public class FireComponent implements EntityComponent {
 
 	@Override
 	public void delete() {
-		fire0.delete();
+		recycler.delete();
-		fire1.delete();
 	}
 
 	private record FireMesh(TextureAtlasSprite sprite) implements QuadMesh {

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

@@ -0,0 +1,10 @@
+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

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