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

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;

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;

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);

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;

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

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];
+}

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);

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[];

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;
+}

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);

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;

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.

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
 }

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);

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;

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();