[WIP] major rewrite, grass and leaves working already

src/main/kotlin/mods/betterfoliage/render/lighting/VanillaAoCalculation.kt

@@ -0,0 +1,147 @@
+package mods.betterfoliage.render.lighting
+
+import mods.betterfoliage.chunk.BlockCtx
+import net.minecraft.block.BlockState
+import net.minecraft.client.renderer.BlockModelRenderer
+import net.minecraft.util.Direction
+import net.minecraft.util.math.BlockPos
+import net.minecraft.world.ILightReader
+
+data class LightingData(
+    @JvmField var packedLight: Int = 0,
+    @JvmField var colorMultiplier: Float = 1.0f
+) {
+    fun mixFrom(corner: LightingData, side1: LightingData, side2: LightingData, center: LightingData) {
+        colorMultiplier =
+            (center.colorMultiplier + side1.colorMultiplier + side2.colorMultiplier + corner.colorMultiplier) * 0.25f
+        packedLight = (
+                center.packedLight +
+                (side1.packedLight.takeUnless { it == 0 } ?: center.packedLight) +
+                (side2.packedLight.takeUnless { it == 0 } ?: center.packedLight) +
+                (corner.packedLight.takeUnless { it == 0 } ?: center.packedLight)
+            ).let { sum -> (sum shr 2) and 0xFF00FF }
+    }
+}
+
+/**
+ * Replacement for [BlockModelRenderer.AmbientOcclusionFace]
+ * This gets called on a LOT, so object instantiation is avoided.
+ * Not thread-safe, always use a [ThreadLocal] instance
+ */
+class VanillaAoCalculator {
+    lateinit var world: ILightReader
+
+    /** [blockPos] is used to get block-related information (i.e. tint, opacity, etc.)
+     *  [lightPos] is used to get light-related information
+     *  this facilitates masquerade rendering of blocks */
+    lateinit var blockPos: BlockPos
+    lateinit var lightPos: BlockPos
+
+    private val probe = LightProbe(BlockModelRenderer.CACHE_COMBINED_LIGHT.get())
+
+    val isValid = BooleanArray(6)
+    val aoData = Array(24) { LightingData() }
+
+    // scratchpad values used during calculation
+    private val centerAo = LightingData()
+    private val sideAo = Array(4) { LightingData() }
+    private val cornerAo = Array(4) { LightingData() }
+    private val isOccluded = BooleanArray(4)
+
+    fun reset(ctx: BlockCtx) {
+        world = ctx.world; blockPos = ctx.pos; lightPos = ctx.pos
+        (0 until 6).forEach { isValid[it] = false }
+    }
+
+    fun fillLightData(lightFace: Direction, isOpaque: Boolean? = null) {
+        if (!isValid[lightFace.ordinal]) calculate(lightFace, isOpaque)
+    }
+
+    /**
+     * Replicate [BlockModelRenderer.AmbientOcclusionFace.updateVertexBrightness]
+     * Does not handle interpolation for non-cubic models, that should be
+     * done in a [VanillaVertexLighter]
+     * @param lightFace face of the block to calculate
+     * @param forceFull force full-block status for lighting calculation, null for auto
+     */
+    private fun calculate(lightFace: Direction, forceFull: Boolean?) {
+        if (isValid[lightFace.ordinal]) return
+        val sideHelper = AoSideHelper.forSide[lightFace.ordinal]
+
+        // Bit 0 of the bitset in vanilla calculations
+        // true if the block model is planar with the block boundary
+        val isFullBlock = forceFull ?: world.getBlockState(blockPos).isCollisionShapeOpaque(world, blockPos)
+
+        val lightOrigin = if (isFullBlock) lightPos.offset(lightFace) else lightPos
+
+        // AO calculation for the face center
+        probe.position { setPos(lightOrigin) }.writeTo(centerAo)
+        if (!isFullBlock && !probe.position { move(lightFace) }.state.isOpaqueCube(world, probe.pos)) {
+            // if the neighboring block in the lightface direction is
+            // transparent (non-opaque), use its packed light instead of our own
+            // (if our block is a full block, we are already using this value)
+            centerAo.packedLight = probe.packedLight
+        }
+
+        // AO calculation for the 4 sides
+        sideHelper.sides.forEachIndexed { sideIdx, sideDir ->
+            // record light data in the block 1 step to the side
+            probe.position { setPos(lightOrigin).move(sideDir) }.writeTo(sideAo[sideIdx])
+            // side is considered occluded if the block 1 step to that side and
+            // 1 step forward (in the lightface direction) is not fully transparent
+            isOccluded[sideIdx] = probe.position { move(lightFace) }.isNonTransparent
+        }
+
+        // AO Calculation for the 4 corners
+        AoSideHelper.faceCornersIdx.forEachIndexed { cornerIdx, sideIndices ->
+            val bothOccluded = isOccluded[sideIndices.first] && isOccluded[sideIndices.second]
+            if (bothOccluded) cornerAo[cornerIdx].apply {
+                // if both sides are occluded, just use the packed light for one of the sides instead
+                val copyFrom = sideAo[sideIndices.first]
+                packedLight = copyFrom.packedLight; colorMultiplier = copyFrom.colorMultiplier
+            }
+            else {
+                // lookup actual packed light from the cornering block in the world
+                probe.position {
+                    setPos(lightOrigin)
+                        .move(sideHelper.sides[sideIndices.first])
+                        .move(sideHelper.sides[sideIndices.second])
+                }.writeTo(cornerAo[cornerIdx])
+            }
+        }
+
+        // Calculate and store final interpolated value for each corner
+        AoSideHelper.faceCornersIdx.forEachIndexed { cornerIdx, sideIndices ->
+            val aoIdx = sideHelper.aoIndex[cornerIdx]
+            aoData[aoIdx].mixFrom(
+                cornerAo[cornerIdx],
+                sideAo[sideIndices.first],
+                sideAo[sideIndices.second],
+                centerAo
+            )
+        }
+        isValid[lightFace.ordinal] = true
+    }
+
+    inner class LightProbe(
+        val cache: BlockModelRenderer.Cache
+    ) {
+        lateinit var state: BlockState
+        val pos = BlockPos.Mutable()
+
+        val packedLight: Int get() = cache.getPackedLight(state, world, pos)
+        val colorMultiplier: Float get() = cache.getBrightness(state, world, pos)
+        val isNonTransparent: Boolean get() = state.getOpacity(world, pos) > 0
+
+        fun writeTo(data: LightingData) {
+            data.packedLight = packedLight
+            data.colorMultiplier = colorMultiplier
+        }
+
+        inline fun position(func: BlockPos.Mutable.() -> Unit): LightProbe {
+            pos.func()
+            state = world.getBlockState(pos)
+            return this
+        }
+    }
+}