Miscellaneous feature level 0 fixes

Fix edge case where an empty struct could be generated in an ESSL 1.0 shader.

Include _maskThreshold and _doubleSided in ESSL 1.0 shaders.

Add GL_OES_standard_derivatives extension to ESSL 1.0 shaders. According to
gpuinfo.org, this has 96% device coverage and supports both Mali-400 and Adreno
(TM) 304.

Remove 3D sampler support from ESSL 1.0 shaders. This extension is only
supported by 62% of devices.

Change filagui material to a FL0 material.

NEW_RELEASE_NOTES.md

@@ -15,3 +15,6 @@ appropriate header in [RELEASE_NOTES.md](./RELEASE_NOTES.md).
 - matinfo: Add support for viewing ESSL 1.0 shaders
 - engine: Add `Renderer::getClearOptions()` [b/243846268]
 - engine: Fix stable shadows (again) when an IBL rotation is used
+- matc: Enable `GL_OES_standard_derivatives` extension in ESSL 1.0 shaders
+- matc: Fix code generation of double sided and masked materials in ESSL 1.0 shaders
+- filagui: Add support for feature level 0

libs/filabridge/include/private/filament/BufferInterfaceBlock.h

@@ -160,6 +160,8 @@ class BufferInterfaceBlock {
 
     bool isEmpty() const noexcept { return mFieldInfoList.empty(); }
 
+    bool isEmptyForFeatureLevel(backend::FeatureLevel featureLevel) const noexcept;
+
     Alignment getAlignment() const noexcept { return mAlignment; }
 
     Target getTarget() const noexcept { return mTarget; }

libs/filabridge/src/BufferInterfaceBlock.cpp

@@ -171,6 +171,14 @@ BufferInterfaceBlock::FieldInfo const* BufferInterfaceBlock::getFieldInfo(
     return &mFieldInfoList[pos->second];
 }
 
+bool BufferInterfaceBlock::isEmptyForFeatureLevel(
+        backend::FeatureLevel featureLevel) const noexcept {
+    return std::all_of(mFieldInfoList.begin(), mFieldInfoList.end(),
+                       [featureLevel](auto const &info) {
+                           return featureLevel < info.minFeatureLevel;
+                       });
+}
+
 uint8_t UTILS_NOINLINE BufferInterfaceBlock::baseAlignmentForType(BufferInterfaceBlock::Type type) noexcept {
     switch (type) {
         case Type::BOOL:
@@ -230,4 +238,3 @@ uint8_t UTILS_NOINLINE BufferInterfaceBlock::strideForType(BufferInterfaceBlock:
 }
 
 } // namespace filament
-

libs/filagui/src/materials/uiBlit.mat

@@ -13,15 +13,16 @@ material {
     shadingModel : unlit,
     culling : none,
     depthCulling: false,
-    blending : transparent
+    blending : transparent,
+    featureLevel : 0
 }
 
 fragment {
     void material(inout MaterialInputs material) {
 	prepareMaterial(material);
         vec2 uv = getUV0();
         uv.y = 1.0 - uv.y;
-        vec4 albedo = texture(materialParams_albedo, uv);
+        vec4 albedo = texture2D(materialParams_albedo, uv);
         material.baseColor = getColor() * albedo;
         material.baseColor.rgb *= material.baseColor.a;
     }

libs/filamat/src/MaterialBuilder.cpp

@@ -587,11 +587,11 @@ void MaterialBuilder::prepareToBuild(MaterialInfo& info) noexcept {
     }
 
     if (mBlendingMode == BlendingMode::MASKED) {
-        ibb.add({{ "_maskThreshold", 0, UniformType::FLOAT }});
+        ibb.add({{ "_maskThreshold", 0, UniformType::FLOAT, Precision::DEFAULT, FeatureLevel::FEATURE_LEVEL_0 }});
     }
 
     if (mDoubleSidedCapability) {
-        ibb.add({{ "_doubleSided", 0, UniformType::BOOL }});
+        ibb.add({{ "_doubleSided", 0, UniformType::BOOL, Precision::DEFAULT, FeatureLevel::FEATURE_LEVEL_0 }});
     }
 
     mRequiredAttributes.set(VertexAttribute::POSITION);

libs/filamat/src/shaders/CodeGenerator.cpp

@@ -63,9 +63,6 @@ utils::io::sstream& CodeGenerator::generateProlog(utils::io::sstream& out, Shade
                     out << "#extension GL_OES_EGL_image_external : require\n\n";
                 }
             }
-            if (material.has3dSamplers && mFeatureLevel == FeatureLevel::FEATURE_LEVEL_0) {
-                out << "#extension GL_OES_texture_3D : require\n\n";
-            }
             if (v.hasInstancedStereo() && stage == ShaderStage::VERTEX) {
                 // If we're not processing the shader through glslang (in the case of unoptimized
                 // OpenGL shaders), then we need to add the #extension string ourselves.
@@ -89,6 +86,10 @@ utils::io::sstream& CodeGenerator::generateProlog(utils::io::sstream& out, Shade
             break;
     }
 
+    if (mFeatureLevel == FeatureLevel::FEATURE_LEVEL_0) {
+        out << "#extension GL_OES_standard_derivatives : require\n\n";
+    }
+
     // This allows our includer system to use the #line directive to denote the source file for
     // #included code. This way, glslang reports errors more accurately.
     out << "#extension GL_GOOGLE_cpp_style_line_directive : enable\n\n";
@@ -554,11 +555,12 @@ io::sstream& CodeGenerator::generateUboAsPlainUniforms(io::sstream& out, ShaderS
 
 io::sstream& CodeGenerator::generateBufferInterfaceBlock(io::sstream& out, ShaderStage stage,
         uint32_t binding, const BufferInterfaceBlock& uib) const {
-    auto const& infos = uib.getFieldInfoList();
-    if (infos.empty()) {
+    if (uib.isEmptyForFeatureLevel(mFeatureLevel)) {
         return out;
     }
 
+    auto const& infos = uib.getFieldInfoList();
+
     if (mTargetLanguage == TargetLanguage::GLSL &&
             mFeatureLevel == FeatureLevel::FEATURE_LEVEL_0) {
         // we need to generate a structure instead