Use world-space dithering as well as a better dither matrix to handle transparency in mipmapping/anisotropic filtering (#1641)

- [x] Prototype
- [x] Remove old code
- [x] ~~Apply this form of dithering to other shaders as well (item
drop)~~ → old dither looks better for items and display model
- [x] Can we finally remove the dither seed?
- [x] Check performance impact → it's slightly (insignificantly) faster
even

assets/cubyz/shaders/chunks/chunk_fragment.frag

@@ -7,9 +7,8 @@ layout(location = 3) in vec2 uv;
 layout(location = 4) flat in vec3 normal;
 layout(location = 5) flat in int textureIndex;
 layout(location = 6) flat in int isBackFace;
-layout(location = 7) flat in int ditherSeed;
-layout(location = 8) flat in float distanceForLodCheck;
-layout(location = 9) flat in int opaqueInLod;
+layout(location = 7) flat in float distanceForLodCheck;
+layout(location = 8) flat in int opaqueInLod;
 
 layout(location = 0) out vec4 fragColor;
 
@@ -17,6 +16,7 @@ layout(binding = 0) uniform sampler2DArray textureSampler;
 layout(binding = 1) uniform sampler2DArray emissionSampler;
 layout(binding = 2) uniform sampler2DArray reflectivityAndAbsorptionSampler;
 layout(binding = 4) uniform samplerCube reflectionMap;
+layout(binding = 5) uniform sampler2D ditherTexture;
 
 layout(location = 5) uniform float reflectionMapSize;
 layout(location = 6) uniform float contrast;
@@ -33,29 +33,13 @@ float lightVariation(vec3 normal) {
 	return baseLighting + dot(normal, directionalPart);
 }
 
-float ditherThresholds[16] = float[16] (
-	1/17.0, 9/17.0, 3/17.0, 11/17.0,
-	13/17.0, 5/17.0, 15/17.0, 7/17.0,
-	4/17.0, 12/17.0, 2/17.0, 10/17.0,
-	16/17.0, 8/17.0, 14/17.0, 6/17.0
-);
-
-ivec2 random1to2(int v) {
-	ivec4 fac = ivec4(11248723, 105436839, 45399083, 5412951);
-	int seed = v.x*fac.x ^ fac.y;
-	return seed*fac.zw;
-}
-
 bool passDitherTest(float alpha) {
 	if(opaqueInLod != 0) {
 		if(distanceForLodCheck > lodDistance) return true;
 		float factor = max(0, distanceForLodCheck - (lodDistance - 32.0))/32.0;
 		alpha = alpha*(1 - factor) + factor;
 	}
-	ivec2 screenPos = ivec2(gl_FragCoord.xy);
-	screenPos += random1to2(ditherSeed);
-	screenPos &= 3;
-	return alpha > ditherThresholds[screenPos.x*4 + screenPos.y];
+	return alpha > texture(ditherTexture, uv).r*255.0/256.0 + 0.5/256.0;
 }
 
 vec4 fixedCubeMapLookup(vec3 v) { // Taken from http://the-witness.net/news/2012/02/seamless-cube-map-filtering/

assets/cubyz/shaders/chunks/chunk_vertex.vert

@@ -7,9 +7,8 @@ layout(location = 3) out vec2 uv;
 layout(location = 4) flat out vec3 normal;
 layout(location = 5) flat out int textureIndex;
 layout(location = 6) flat out int isBackFace;
-layout(location = 7) flat out int ditherSeed;
-layout(location = 8) flat out float distanceForLodCheck;
-layout(location = 9) flat out int opaqueInLod;
+layout(location = 7) flat out float distanceForLodCheck;
+layout(location = 8) flat out int opaqueInLod;
 
 layout(location = 0) uniform vec3 ambientLight;
 layout(location = 1) uniform mat4 projectionMatrix;
@@ -84,7 +83,6 @@ void main() {
 	);
 	light = max(sunLight*ambientLight, blockLight)/31;
 	isBackFace = encodedPositionAndLightIndex>>15 & 1;
-	ditherSeed = encodedPositionAndLightIndex & 15;
 
 	textureIndex = textureAndQuad & 65535;
 	int quadIndex = textureAndQuad >> 16;

assets/cubyz/shaders/chunks/transparent_fragment.frag

@@ -7,9 +7,8 @@ layout(location = 3) in vec2 uv;
 layout(location = 4) flat in vec3 normal;
 layout(location = 5) flat in int textureIndex;
 layout(location = 6) flat in int isBackFace;
-layout(location = 7) flat in int ditherSeed;
-layout(location = 8) flat in float distanceForLodCheck;
-layout(location = 9) flat in int opaqueInLod;
+layout(location = 7) flat in float distanceForLodCheck;
+layout(location = 8) flat in int opaqueInLod;
 
 layout(location = 0, index = 0) out vec4 fragColor;
 layout(location = 0, index = 1) out vec4 blendColor;

src/blocks.zig

@@ -512,6 +512,7 @@ pub const meshes = struct { // MARK: meshes
 	pub var blockTextureArray: TextureArray = undefined;
 	pub var emissionTextureArray: TextureArray = undefined;
 	pub var reflectivityAndAbsorptionTextureArray: TextureArray = undefined;
+	pub var ditherTexture: graphics.Texture = undefined;
 
 	const black: Color = Color{.r = 0, .g = 0, .b = 0, .a = 255};
 	const magenta: Color = Color{.r = 255, .g = 0, .b = 255, .a = 255};
@@ -525,6 +526,7 @@ pub const meshes = struct { // MARK: meshes
 		blockTextureArray = .init();
 		emissionTextureArray = .init();
 		reflectivityAndAbsorptionTextureArray = .init();
+		ditherTexture = .initFromMipmapFiles("assets/cubyz/blocks/textures/dither/", 64, 0.5);
 		textureIDs = .init(main.globalAllocator);
 		animation = .init(main.globalAllocator);
 		blockTextures = .init(main.globalAllocator);
@@ -551,6 +553,7 @@ pub const meshes = struct { // MARK: meshes
 		blockTextureArray.deinit();
 		emissionTextureArray.deinit();
 		reflectivityAndAbsorptionTextureArray.deinit();
+		ditherTexture.deinit();
 		textureIDs.deinit();
 		animation.deinit();
 		blockTextures.deinit();

src/graphics.zig

@@ -2307,6 +2307,38 @@ pub const Texture = struct { // MARK: Texture
 		return self;
 	}
 
+	pub fn initFromMipmapFiles(pathPrefix: []const u8, largestSize: u31, lodBias: f32) Texture {
+		const self = Texture.init();
+		self.bind();
+
+		const maxLod = std.math.log2_int(u31, largestSize);
+
+		var curSize: u31 = largestSize;
+		while(curSize != 0) : (curSize /= 2) {
+			c.glTexImage2D(c.GL_TEXTURE_2D, maxLod - std.math.log2_int(u31, curSize), c.GL_RGBA8, curSize, curSize, 0, c.GL_RGBA, c.GL_UNSIGNED_BYTE, null);
+		}
+
+		curSize = largestSize;
+		while(curSize != 0) : (curSize /= 2) {
+			const path = std.fmt.allocPrint(main.stackAllocator.allocator, "{s}{}.png", .{pathPrefix, curSize}) catch unreachable;
+			defer main.stackAllocator.free(path);
+			const image = Image.readFromFile(main.stackAllocator, path) catch |err| blk: {
+				std.log.err("Couldn't read image from {s}: {s}", .{path, @errorName(err)});
+				break :blk Image.defaultImage;
+			};
+			defer image.deinit(main.stackAllocator);
+			c.glTexSubImage2D(c.GL_TEXTURE_2D, maxLod - std.math.log2_int(u31, curSize), 0, 0, curSize, curSize, c.GL_RGBA, c.GL_UNSIGNED_BYTE, image.imageData.ptr);
+		}
+
+		c.glTexParameteri(c.GL_TEXTURE_2D_ARRAY, c.GL_TEXTURE_MAX_LOD, maxLod);
+		c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_MIN_FILTER, c.GL_NEAREST_MIPMAP_LINEAR);
+		c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_MAG_FILTER, c.GL_NEAREST);
+		c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_WRAP_S, c.GL_REPEAT);
+		c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_WRAP_T, c.GL_REPEAT);
+		c.glTexParameterf(c.GL_TEXTURE_2D, c.GL_TEXTURE_LOD_BIAS, lodBias);
+		return self;
+	}
+
 	pub fn deinit(self: Texture) void {
 		c.glDeleteTextures(1, &self.textureID);
 	}

src/renderer.zig

@@ -213,6 +213,8 @@ pub fn renderWorld(world: *World, ambientLight: Vec3f, skyColor: Vec3f, playerPo
 	blocks.meshes.emissionTextureArray.bind();
 	c.glActiveTexture(c.GL_TEXTURE2);
 	blocks.meshes.reflectivityAndAbsorptionTextureArray.bind();
+	c.glActiveTexture(c.GL_TEXTURE5);
+	blocks.meshes.ditherTexture.bind();
 	reflectionCubeMap.bindTo(4);
 
 	chunk_meshing.quadsDrawn = 0;