From b7c8604898b8b0c2efdc6f68101ef14a5e3a3322 Mon Sep 17 00:00:00 2001
From: Jozufozu <jozsefaug@gmail.com>
Date: Fri, 5 Jul 2024 19:27:26 -0700
Subject: [PATCH] Light in the shade

- Expose light in the shader api
  - flw_light - for builtin smooth lighting, faster than can be
    implemented by materials alone
  - flw_lightFetch - for materials that want to go crazy, access to raw
    data
---
 .../backend/compile/ContextShader.java         |  3 ++-
 .../flywheel/flywheel/internal/api_impl.frag   |  1 +
 .../flywheel/flywheel/internal/api_impl.glsl   |  7 +++++++
 .../flywheel/flywheel/internal/api_impl.vert   |  1 +
 .../flywheel/flywheel/internal/common.frag     |  9 ---------
 .../flywheel/internal/indirect/light.glsl      | 17 +++++++++++++++++
 .../flywheel/internal/indirect/main.frag       | 18 +-----------------
 .../flywheel/internal/indirect/main.vert       |  1 +
 .../flywheel/internal/instancing/light.glsl    | 12 ++++++++++++
 .../flywheel/internal/instancing/main.frag     | 13 +------------
 .../flywheel/internal/instancing/main.vert     |  1 +
 .../flywheel/flywheel/internal/light_lut.glsl  | 18 +++++++++++++++---
 .../flywheel/flywheel/material/default.frag    |  6 ++++++
 docs/shader-api/common.glsl                    |  7 +++++++
 docs/shader-api/fragment.glsl                  |  5 +----
 docs/shader-api/vertex.glsl                    |  5 +----
 16 files changed, 74 insertions(+), 50 deletions(-)
 create mode 100644 common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.glsl
 create mode 100644 common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/light.glsl
 create mode 100644 common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/light.glsl
 create mode 100644 docs/shader-api/common.glsl

diff --git a/common/src/backend/java/dev/engine_room/flywheel/backend/compile/ContextShader.java b/common/src/backend/java/dev/engine_room/flywheel/backend/compile/ContextShader.java
index 6d3fede7a..7c8aac5dd 100644
--- a/common/src/backend/java/dev/engine_room/flywheel/backend/compile/ContextShader.java
+++ b/common/src/backend/java/dev/engine_room/flywheel/backend/compile/ContextShader.java
@@ -13,7 +13,8 @@ public enum ContextShader {
 	DEFAULT(null, $ -> {
 	}),
 	CRUMBLING("_FLW_CRUMBLING", program -> program.setSamplerBinding("_flw_crumblingTex", Samplers.CRUMBLING)),
-	EMBEDDED("_FLW_EMBEDDED", $ -> {});
+	EMBEDDED("FLW_EMBEDDED", $ -> {
+	});
 
 	@Nullable
 	private final String define;
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.frag b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.frag
index dc8334916..af16b80e2 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.frag
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.frag
@@ -1,4 +1,5 @@
 #include "flywheel:internal/material.glsl"
+#include "flywheel:internal/api_impl.glsl"
 #include "flywheel:internal/uniforms/uniforms.glsl"
 
 in vec4 flw_vertexPos;
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.glsl b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.glsl
new file mode 100644
index 000000000..9362c693d
--- /dev/null
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.glsl
@@ -0,0 +1,7 @@
+/// Get the light at the given world position.
+/// This may be interpolated for smooth lighting.
+bool flw_light(vec3 worldPos, out vec2 light);
+
+/// Fetches the light value at the given block position.
+/// Returns false if the light for the given block is not available.
+bool flw_lightFetch(ivec3 blockPos, out vec2 light);
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.vert b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.vert
index d9934d42e..d1e751929 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.vert
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/api_impl.vert
@@ -1,4 +1,5 @@
 #include "flywheel:internal/material.glsl"
+#include "flywheel:internal/api_impl.glsl"
 #include "flywheel:internal/uniforms/uniforms.glsl"
 
 out vec4 flw_vertexPos;
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/common.frag b/common/src/backend/resources/assets/flywheel/flywheel/internal/common.frag
index 2cfa92e96..23df5b7e9 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/common.frag
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/common.frag
@@ -13,8 +13,6 @@ uniform sampler2D _flw_crumblingTex;
 in vec2 _flw_crumblingTexCoord;
 #endif
 
-bool _flw_embeddedLight(vec3 worldPos, out vec2 lightCoord);
-
 flat in uint _flw_instanceID;
 
 out vec4 _flw_outputColor;
@@ -37,13 +35,6 @@ void _flw_main() {
     flw_fragOverlay = flw_vertexOverlay;
     flw_fragLight = flw_vertexLight;
 
-    #ifdef _FLW_EMBEDDED
-    vec2 embeddedLight;
-    if (_flw_embeddedLight(flw_vertexPos.xyz, embeddedLight)) {
-        flw_fragLight = max(flw_fragLight, embeddedLight);
-    }
-    #endif
-
     flw_materialFragment();
 
     #ifdef _FLW_CRUMBLING
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/light.glsl b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/light.glsl
new file mode 100644
index 000000000..bd688ef28
--- /dev/null
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/light.glsl
@@ -0,0 +1,17 @@
+#include "flywheel:internal/light_lut.glsl"
+
+layout(std430, binding = _FLW_LIGHT_LUT_BINDING) restrict readonly buffer LightLut {
+    uint _flw_lightLut[];
+};
+
+layout(std430, binding = _FLW_LIGHT_SECTIONS_BINDING) restrict readonly buffer LightSections {
+    uint _flw_lightSections[];
+};
+
+uint _flw_indexLut(uint index) {
+    return _flw_lightLut[index];
+}
+
+uint _flw_indexLight(uint index) {
+    return _flw_lightSections[index];
+}
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.frag b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.frag
index 1711390a6..b1dbb0822 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.frag
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.frag
@@ -1,25 +1,9 @@
 #include "flywheel:internal/common.frag"
-#include "flywheel:internal/light_lut.glsl"
 #include "flywheel:internal/indirect/buffer_bindings.glsl"
+#include "flywheel:internal/indirect/light.glsl"
 
 flat in uvec3 _flw_packedMaterial;
 
-layout(std430, binding = _FLW_LIGHT_LUT_BINDING) restrict readonly buffer LightLut {
-    uint _flw_lightLut[];
-};
-
-layout(std430, binding = _FLW_LIGHT_SECTIONS_BINDING) restrict readonly buffer LightSections {
-    uint _flw_lightSections[];
-};
-
-uint _flw_indexLut(uint index) {
-    return _flw_lightLut[index];
-}
-
-uint _flw_indexLight(uint index) {
-    return _flw_lightSections[index];
-}
-
 void main() {
     _flw_uberMaterialFragmentIndex = _flw_packedMaterial.x;
     _flw_unpackUint2x16(_flw_packedMaterial.y, _flw_uberCutoutIndex, _flw_uberFogIndex);
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.vert b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.vert
index 55bd8fc0f..a95d31662 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.vert
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/indirect/main.vert
@@ -2,6 +2,7 @@
 #include "flywheel:internal/packed_material.glsl"
 #include "flywheel:internal/indirect/buffer_bindings.glsl"
 #include "flywheel:internal/indirect/draw_command.glsl"
+#include "flywheel:internal/indirect/light.glsl"
 
 layout(std430, binding = _FLW_TARGET_BUFFER_BINDING) restrict readonly buffer TargetBuffer {
     uint _flw_instanceIndices[];
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/light.glsl b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/light.glsl
new file mode 100644
index 000000000..f023322a4
--- /dev/null
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/light.glsl
@@ -0,0 +1,12 @@
+#include "flywheel:internal/light_lut.glsl"
+
+uniform usamplerBuffer _flw_lightLut;
+uniform usamplerBuffer _flw_lightSections;
+
+uint _flw_indexLut(uint index) {
+    return texelFetch(_flw_lightLut, int(index)).r;
+}
+
+uint _flw_indexLight(uint index) {
+    return texelFetch(_flw_lightSections, int(index)).r;
+}
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.frag b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.frag
index 80a4402ea..89b09b37f 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.frag
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.frag
@@ -1,19 +1,8 @@
 #include "flywheel:internal/common.frag"
-#include "flywheel:internal/light_lut.glsl"
+#include "flywheel:internal/instancing/light.glsl"
 
 uniform uvec4 _flw_packedMaterial;
 
-uniform usamplerBuffer _flw_lightLut;
-uniform usamplerBuffer _flw_lightSections;
-
-uint _flw_indexLut(uint index) {
-    return texelFetch(_flw_lightLut, int(index)).r;
-}
-
-uint _flw_indexLight(uint index) {
-    return texelFetch(_flw_lightSections, int(index)).r;
-}
-
 void main() {
     _flw_uberMaterialFragmentIndex = _flw_packedMaterial.y;
     _flw_unpackUint2x16(_flw_packedMaterial.z, _flw_uberCutoutIndex, _flw_uberFogIndex);
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.vert b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.vert
index 8c4b9d6a3..4b6914eae 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.vert
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/instancing/main.vert
@@ -1,5 +1,6 @@
 #include "flywheel:internal/common.vert"
 #include "flywheel:internal/packed_material.glsl"
+#include "flywheel:internal/instancing/light.glsl"
 
 uniform uvec4 _flw_packedMaterial;
 uniform int _flw_baseInstance = 0;
diff --git a/common/src/backend/resources/assets/flywheel/flywheel/internal/light_lut.glsl b/common/src/backend/resources/assets/flywheel/flywheel/internal/light_lut.glsl
index e6abff4fa..f79b5a20a 100644
--- a/common/src/backend/resources/assets/flywheel/flywheel/internal/light_lut.glsl
+++ b/common/src/backend/resources/assets/flywheel/flywheel/internal/light_lut.glsl
@@ -64,7 +64,21 @@ vec2 _flw_lightAt(uint sectionOffset, uvec3 blockInSectionPos) {
     return vec2(block, sky);
 }
 
-bool _flw_embeddedLight(vec3 worldPos, out vec2 lightCoord) {
+bool flw_lightFetch(ivec3 blockPos, out vec2 lightCoord) {
+    uint lightSectionIndex;
+    if (_flw_chunkCoordToSectionIndex(blockPos >> 4, lightSectionIndex)) {
+        return false;
+    }
+    // The offset of the section in the light buffer.
+    uint sectionOffset = lightSectionIndex * _FLW_LIGHT_SECTION_SIZE_INTS;
+
+    uvec3 blockInSectionPos = (blockPos & 0xF) + 1;
+
+    lightCoord = _flw_lightAt(sectionOffset, blockInSectionPos) / 15.;
+    return true;
+}
+
+bool flw_light(vec3 worldPos, out vec2 lightCoord) {
     // Always use the section of the block we are contained in to ensure accuracy.
     // We don't want to interpolate between sections, but also we might not be able
     // to rely on the existence neighboring sections, so don't do any extra rounding here.
@@ -72,8 +86,6 @@ bool _flw_embeddedLight(vec3 worldPos, out vec2 lightCoord) {
 
     uint lightSectionIndex;
     if (_flw_chunkCoordToSectionIndex(blockPos >> 4, lightSectionIndex)) {
-        // TODO: useful debug mode for this.
-        // flw_fragOverlay = ivec2(0, 3);
         return false;
     }
     // The offset of the section in the light buffer.
diff --git a/common/src/lib/resources/assets/flywheel/flywheel/material/default.frag b/common/src/lib/resources/assets/flywheel/flywheel/material/default.frag
index 68dfe9a5b..42b1ac1fc 100644
--- a/common/src/lib/resources/assets/flywheel/flywheel/material/default.frag
+++ b/common/src/lib/resources/assets/flywheel/flywheel/material/default.frag
@@ -1,2 +1,8 @@
 void flw_materialFragment() {
+    #ifdef FLW_EMBEDDED
+    vec2 embeddedLight;
+    if (flw_light(flw_vertexPos.xyz, embeddedLight)) {
+        flw_fragLight = max(flw_fragLight, embeddedLight);
+    }
+    #endif
 }
diff --git a/docs/shader-api/common.glsl b/docs/shader-api/common.glsl
new file mode 100644
index 000000000..9362c693d
--- /dev/null
+++ b/docs/shader-api/common.glsl
@@ -0,0 +1,7 @@
+/// Get the light at the given world position.
+/// This may be interpolated for smooth lighting.
+bool flw_light(vec3 worldPos, out vec2 light);
+
+/// Fetches the light value at the given block position.
+/// Returns false if the light for the given block is not available.
+bool flw_lightFetch(ivec3 blockPos, out vec2 light);
diff --git a/docs/shader-api/fragment.glsl b/docs/shader-api/fragment.glsl
index a99837c25..e13ec6588 100644
--- a/docs/shader-api/fragment.glsl
+++ b/docs/shader-api/fragment.glsl
@@ -1,4 +1,5 @@
 #include "flywheel:api/material.glsl"
+#include "flywheel:api/common.glsl"
 
 /*const*/ vec4 flw_vertexPos;
 /*const*/ vec4 flw_vertexColor;
@@ -24,10 +25,6 @@ vec4 flw_fogFilter(vec4 color);
 // To be implemented by discard shaders.
 bool flw_discardPredicate(vec4 finalColor);
 
-// To be implemented by the context shader.
-void flw_beginFragment();
-void flw_endFragment();
-
 sampler2D flw_diffuseTex;
 sampler2D flw_overlayTex;
 sampler2D flw_lightTex;
diff --git a/docs/shader-api/vertex.glsl b/docs/shader-api/vertex.glsl
index 338923540..5dcab38e7 100644
--- a/docs/shader-api/vertex.glsl
+++ b/docs/shader-api/vertex.glsl
@@ -1,4 +1,5 @@
 #include "flywheel:api/material.glsl"
+#include "flywheel:api/common.glsl"
 
 vec4 flw_vertexPos;
 vec4 flw_vertexColor;
@@ -17,7 +18,3 @@ void flw_transformBoundingSphere(in FlwInstance i, inout vec3 center, inout floa
 
 // To be implemented by the material vertex shader.
 void flw_materialVertex();
-
-// To be implemented by the context shader.
-void flw_beginVertex();
-void flw_endVertex();