The boring way

- Just use vanilla's implementation for crumbling.

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancedCrumbling.java

@@ -6,7 +6,6 @@ import java.util.List;
 import java.util.Map;
 
 import org.jetbrains.annotations.NotNull;
-import org.lwjgl.opengl.GL32;
 
 import com.jozufozu.flywheel.api.backend.Engine;
 import com.jozufozu.flywheel.api.instance.Instance;
@@ -22,12 +21,11 @@ import com.mojang.blaze3d.systems.RenderSystem;
 import it.unimi.dsi.fastutil.ints.Int2ObjectArrayMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import net.minecraft.client.resources.model.ModelBakery;
-import net.minecraft.core.BlockPos;
 
-public class InstancingCrumble {
+public class InstancedCrumbling {
 	@NotNull
-	public static Map<ShaderState, Int2ObjectMap<Map<BlockPos, List<Runnable>>>> doCrumblingSort(List<Engine.CrumblingBlock> instances) {
+	public static Map<ShaderState, Int2ObjectMap<List<Runnable>>> doCrumblingSort(List<Engine.CrumblingBlock> instances) {
-		Map<ShaderState, Int2ObjectMap<Map<BlockPos, List<Runnable>>>> out = new HashMap<>();
+		Map<ShaderState, Int2ObjectMap<List<Runnable>>> out = new HashMap<>();
 
 		for (Engine.CrumblingBlock triple : instances) {
 			int progress = triple.progress();
@@ -36,8 +34,6 @@ public class InstancingCrumble {
 				continue;
 			}
 
-			BlockPos position = triple.pos();
-
 			for (Instance instance : triple.instances()) {
 				// Filter out instances that weren't created by this engine.
 				// If all is well, we probably shouldn't take the `continue`
@@ -55,8 +51,7 @@ public class InstancingCrumble {
 
 				for (DrawCall draw : draws) {
 					out.computeIfAbsent(draw.shaderState, $ -> new Int2ObjectArrayMap<>())
-							.computeIfAbsent(progress, $ -> new HashMap<>())
+							.computeIfAbsent(progress, $ -> new ArrayList<>())
-							.computeIfAbsent(position, $ -> new ArrayList<>())
 							.add(() -> draw.renderOne(impl));
 				}
 			}
@@ -64,7 +59,7 @@ public class InstancingCrumble {
 		return out;
 	}
 
-	public static void render(List<Engine.CrumblingBlock> crumblingBlocks, BlockPos renderOrigin) {
+	public static void render(List<Engine.CrumblingBlock> crumblingBlocks) {
 		// Sort draw calls into buckets, so we don't have to do as many shader binds.
 		var byShaderState = doCrumblingSort(crumblingBlocks);
 
@@ -88,16 +83,14 @@ public class InstancingCrumble {
 						.get(shader.vertexType(), shader.instanceType(), Contexts.CRUMBLING);
 				UniformBuffer.syncAndBind(program);
 
-				int crumblingBlockPosUniform = program.getUniformLocation("_flw_crumblingBlockPos");
-
 				InstancingEngine.uploadMaterialIDUniform(program, material);
 
 				int renderTex = getDiffuseTexture(material);
 
-				for (Int2ObjectMap.Entry<Map<BlockPos, List<Runnable>>> progressEntry : byProgress.int2ObjectEntrySet()) {
+				for (Int2ObjectMap.Entry<List<Runnable>> progressEntry : byProgress.int2ObjectEntrySet()) {
-					var byPos = progressEntry.getValue();
+					var drawCalls = progressEntry.getValue();
 
-					if (byPos.isEmpty()) {
+					if (drawCalls.isEmpty()) {
 						continue;
 					}
 
@@ -109,12 +102,7 @@ public class InstancingCrumble {
 					GlTextureUnit.T1.makeActive();
 					RenderSystem.bindTexture(renderTex);
 
-					for (var blockPosEntry : byPos.entrySet()) {
+					drawCalls.forEach(Runnable::run);
-						var center = blockPosEntry.getKey().getCenter();
-						GL32.glUniform3f(crumblingBlockPosUniform, (float) center.x - renderOrigin.getX(), (float) center.y - renderOrigin.getY(), (float) center.z - renderOrigin.getZ());
-
-						blockPosEntry.getValue().forEach(Runnable::run);
-					}
 				}
 			}
 		}

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancingEngine.java

@@ -76,7 +76,7 @@ public class InstancingEngine extends AbstractEngine {
 		// Need to wait for flush before we can inspect instancer state.
 		executor.syncUntil(flushFlag::isRaised);
 
-		InstancingCrumble.render(crumblingBlocks, this.renderOrigin);
+		InstancedCrumbling.render(crumblingBlocks);
 	}
 
 	@Override

src/main/resources/assets/flywheel/flywheel/context/crumbling.frag

@@ -7,39 +7,17 @@ layout (depth_greater) out float gl_FragDepth;
 #endif
 #endif
 
-uniform vec3 _flw_crumblingBlockPos;
-
 uniform sampler2D flw_diffuseTex;
 uniform sampler2D flw_crumblingTex;
 
-in vec2 _flw_crumblingFlip;
+in vec2 _flw_crumblingTexCoord;
 
 out vec4 fragColor;
 
 vec4 flw_crumblingSampleColor;
 
-vec2 flattenedPos(vec3 pos, vec3 normal) {
-    pos = pos - _flw_crumblingBlockPos;
-
-    // https://community.khronos.org/t/52861
-    vec3 Q1 = dFdx(pos);
-    vec3 Q2 = dFdy(pos);
-    vec2 st1 = dFdx(flw_vertexTexCoord);
-    vec2 st2 = dFdy(flw_vertexTexCoord);
-
-    vec3 T = normalize(Q1*st2.t - Q2*st1.t);
-    vec3 B = normalize(-Q1*st2.s + Q2*st1.s);
-
-    mat3 tbn = mat3(T, B, normal);
-
-    // transpose is the same as inverse for orthonormal matrices
-    return ((transpose(tbn) * pos).xy + vec2(0.5)) * _flw_crumblingFlip;
-}
-
 void flw_initFragment() {
-    vec2 crumblingTexCoord = flattenedPos(flw_vertexPos.xyz, flw_vertexNormal);
+    flw_crumblingSampleColor = texture(flw_crumblingTex, _flw_crumblingTexCoord);
-
-    flw_crumblingSampleColor = texture(flw_crumblingTex, crumblingTexCoord);
     flw_sampleColor = texture(flw_diffuseTex, flw_vertexTexCoord);
 
     // Let the other components modify the diffuse color as they normally would.

src/main/resources/assets/flywheel/flywheel/context/crumbling.vert

@@ -1,7 +1,7 @@
 #include "flywheel:api/vertex.glsl"
 #include "flywheel:util/fog.glsl"
 
-out vec2 _flw_crumblingFlip;
+out vec2 _flw_crumblingTexCoord;
 
 const int DOWN = 0;
 const int UP = 1;
@@ -10,20 +10,13 @@ const int SOUTH = 3;
 const int WEST = 4;
 const int EAST = 5;
 
-const vec2 FLIPS_BY_FACE[6] = vec2[](
-    vec2(1., -1.),
-    vec2(-1., -1.),
-    vec2(-1., -1.),
-    vec2(-1., -1.),
-    vec2(1., -1.),
-    vec2(1., -1.)
-);
-
 // based on net.minecraftforge.client.ForgeHooksClient.getNearestStable
 int getNearestFacing(vec3 normal) {
     float maxAlignment = -2;
     int face = 2;
 
+    // Calculate the alignment of the normal vector with each axis.
+    // Note that `-dot(normal, axis) == dot(normal, -axis)`.
     vec3 alignment = vec3(
     dot(normal, vec3(1., 0., 0.)),
     dot(normal, vec3(0., 1., 0.)),
@@ -46,44 +39,39 @@ int getNearestFacing(vec3 normal) {
         maxAlignment = alignment.z;
         face = SOUTH;
     }
-    if (alignment.x > maxAlignment) {
+    if (-alignment.x > maxAlignment) {
         maxAlignment = -alignment.x;
         face = WEST;
     }
+    if (alignment.x > maxAlignment) {
+        maxAlignment = alignment.x;
+        face = EAST;
+    }
 
     return face;
 }
 
-vec2 calculateFlip(vec3 normal) {
+vec2 getCrumblingTexCoord() {
-    int face = getNearestFacing(normal);
+    switch (getNearestFacing(flw_vertexNormal)) {
-    return FLIPS_BY_FACE[face];
+        case DOWN: return vec2(flw_vertexPos.x, -flw_vertexPos.z);
-}
+        case UP: return vec2(flw_vertexPos.x, flw_vertexPos.z);
+        case NORTH: return vec2(-flw_vertexPos.x, -flw_vertexPos.y);
+        case SOUTH: return vec2(flw_vertexPos.x, -flw_vertexPos.y);
+        case WEST: return vec2(-flw_vertexPos.z, -flw_vertexPos.y);
+        case EAST: return vec2(flw_vertexPos.z, -flw_vertexPos.y);
+    }
 
-// This is disgusting so if an issue comes up just throw this away and fix the branching version above.
+    // default to north
-vec2 calculateFlipBranchless(vec3 normal) {
+    return vec2(-flw_vertexPos.x, -flw_vertexPos.y);
-    vec3 alignment = vec3(
-    dot(normal, vec3(1., 0., 0.)),
-    dot(normal, vec3(0., 1., 0.)),
-    dot(normal, vec3(0., 0., 1.))
-    );
-
-    vec3 absAlignment = abs(alignment);
-
-    // x is the max alignment that would cause U to be -1.
-    // y is the max alignment that would cause U to be 1.
-    vec2 maxNegativeMaxPositive = max(vec2(absAlignment.z, alignment.y), vec2(-alignment.y, absAlignment.x));
-
-    bool flipU = maxNegativeMaxPositive.x > maxNegativeMaxPositive.y;
-
-    return vec2(mix(1., -1., flipU), -1.);
 }
 
 void flw_initVertex() {
-    // Calculate the flips in model space so that the crumbling effect doesn't have discontinuities.
+    // no-op
-    _flw_crumblingFlip = calculateFlipBranchless(flw_vertexNormal);
 }
 
 void flw_contextVertex() {
+    _flw_crumblingTexCoord = getCrumblingTexCoord();
+
     flw_distance = fog_distance(flw_vertexPos.xyz, flywheel.cameraPos.xyz, flywheel.fogShape);
     gl_Position = flywheel.viewProjection * flw_vertexPos;
     flw_vertexNormal = normalize(flw_vertexNormal);