[core, ios, macos, android, node] Heatmap layer (#11046)

Co-Authored-By: Konstantin Käfer <mail@kkaefer.com>
Co-Authored-By: Anand Thakker <anandthakker@users.noreply.github.com>
Co-Authored-By: Minh Nguyễn <1ec5@users.noreply.github.com>

4 files changed, 56 insertions, 12 deletions

diff --git a/src/mbgl/gl/color_mode.hpp b/src/mbgl/gl/color_mode.hpp
index c6594a3a77..e394f43501 100644
--- a/src/mbgl/gl/color_mode.hpp
+++ b/src/mbgl/gl/color_mode.hpp
@@ -85,6 +85,10 @@ public:
     static ColorMode alphaBlended() {
         return ColorMode { Add { One, OneMinusSrcAlpha }, {}, { true, true, true, true } };
     }
+
+    static ColorMode additive() {
+        return ColorMode { Add { One, One }, {}, { true, true, true, true } };
+    }
 };
 
 constexpr bool operator!=(const ColorMode::Mask& a, const ColorMode::Mask& b) {
diff --git a/src/mbgl/gl/context.cpp b/src/mbgl/gl/context.cpp
index b6244d58c7..f40cfa1f2c 100644
--- a/src/mbgl/gl/context.cpp
+++ b/src/mbgl/gl/context.cpp
@@ -60,6 +60,16 @@ static_assert(std::is_same<std::underlying_type_t<TextureFormat>, GLenum>::value
 static_assert(underlying_type(TextureFormat::RGBA) == GL_RGBA, "OpenGL type mismatch");
 static_assert(underlying_type(TextureFormat::Alpha) == GL_ALPHA, "OpenGL type mismatch");
 
+static_assert(std::is_same<std::underlying_type_t<TextureType>, GLenum>::value, "OpenGL type mismatch");
+static_assert(underlying_type(TextureType::UnsignedByte) == GL_UNSIGNED_BYTE, "OpenGL type mismatch");
+
+#if MBGL_USE_GLES2 && GL_HALF_FLOAT_OES
+static_assert(underlying_type(TextureType::HalfFloat) == GL_HALF_FLOAT_OES, "OpenGL type mismatch");
+#endif
+#if !MBGL_USE_GLES2 && GL_HALF_FLOAT_ARB
+static_assert(underlying_type(TextureType::HalfFloat) == GL_HALF_FLOAT_ARB, "OpenGL type mismatch");
+#endif
+
 static_assert(underlying_type(UniformDataType::Float) == GL_FLOAT, "OpenGL type mismatch");
 static_assert(underlying_type(UniformDataType::FloatVec2) == GL_FLOAT_VEC2, "OpenGL type mismatch");
 static_assert(underlying_type(UniformDataType::FloatVec3) == GL_FLOAT_VEC3, "OpenGL type mismatch");
@@ -116,6 +126,19 @@ void Context::initializeExtensions(const std::function<gl::ProcAddress(const cha
         programBinary = std::make_unique<extension::ProgramBinary>(fn);
 #endif
 
+#if MBGL_USE_GLES2
+        constexpr const char* halfFloatExtensionName = "OES_texture_half_float";
+        constexpr const char* halfFloatColorBufferExtensionName = "EXT_color_buffer_half_float";
+#else
+        constexpr const char* halfFloatExtensionName = "ARB_half_float_pixel";
+        constexpr const char* halfFloatColorBufferExtensionName = "ARB_color_buffer_float";
+#endif
+        if (strstr(extensions, halfFloatExtensionName) != nullptr &&
+            strstr(extensions, halfFloatColorBufferExtensionName) != nullptr) {
+
+            supportsHalfFloatTextures = true;
+        }
+
         if (!supportsVertexArrays()) {
             Log::Warning(Event::OpenGL, "Not using Vertex Array Objects");
         }
@@ -491,10 +514,10 @@ Context::createFramebuffer(const Texture& color,
 }
 
 UniqueTexture
-Context::createTexture(const Size size, const void* data, TextureFormat format, TextureUnit unit) {
+Context::createTexture(const Size size, const void* data, TextureFormat format, TextureUnit unit, TextureType type) {
     auto obj = createTexture();
     pixelStoreUnpack = { 1 };
-    updateTexture(obj, size, data, format, unit);
+    updateTexture(obj, size, data, format, unit, type);
     // We are using clamp to edge here since OpenGL ES doesn't allow GL_REPEAT on NPOT textures.
     // We use those when the pixelRatio isn't a power of two, e.g. on iPhone 6 Plus.
     MBGL_CHECK_ERROR(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE));
@@ -505,11 +528,11 @@ Context::createTexture(const Size size, const void* data, TextureFormat format,
 }
 
 void Context::updateTexture(
-    TextureID id, const Size size, const void* data, TextureFormat format, TextureUnit unit) {
+    TextureID id, const Size size, const void* data, TextureFormat format, TextureUnit unit, TextureType type) {
     activeTextureUnit = unit;
     texture[unit] = id;
     MBGL_CHECK_ERROR(glTexImage2D(GL_TEXTURE_2D, 0, static_cast<GLenum>(format), size.width,
-                                  size.height, 0, static_cast<GLenum>(format), GL_UNSIGNED_BYTE,
+                                  size.height, 0, static_cast<GLenum>(format), static_cast<GLenum>(type),
                                   data));
 }
 
diff --git a/src/mbgl/gl/context.hpp b/src/mbgl/gl/context.hpp
index 14f078367f..67624288e2 100644
--- a/src/mbgl/gl/context.hpp
+++ b/src/mbgl/gl/context.hpp
@@ -125,23 +125,29 @@ public:
 
     // Create a texture from an image with data.
     template <typename Image>
-    Texture createTexture(const Image& image, TextureUnit unit = 0) {
+    Texture createTexture(const Image& image,
+                          TextureUnit unit = 0,
+                          TextureType type = TextureType::UnsignedByte) {
         auto format = image.channels == 4 ? TextureFormat::RGBA : TextureFormat::Alpha;
-        return { image.size, createTexture(image.size, image.data.get(), format, unit) };
+        return { image.size, createTexture(image.size, image.data.get(), format, unit, type) };
     }
 
     template <typename Image>
-    void updateTexture(Texture& obj, const Image& image, TextureUnit unit = 0) {
+    void updateTexture(Texture& obj,
+                       const Image& image,
+                       TextureUnit unit = 0,
+                       TextureType type = TextureType::UnsignedByte) {
         auto format = image.channels == 4 ? TextureFormat::RGBA : TextureFormat::Alpha;
-        updateTexture(obj.texture.get(), image.size, image.data.get(), format, unit);
+        updateTexture(obj.texture.get(), image.size, image.data.get(), format, unit, type);
         obj.size = image.size;
     }
 
     // Creates an empty texture with the specified dimensions.
     Texture createTexture(const Size size,
                           TextureFormat format = TextureFormat::RGBA,
-                          TextureUnit unit = 0) {
-        return { size, createTexture(size, nullptr, format, unit) };
+                          TextureUnit unit = 0,
+                          TextureType type = TextureType::UnsignedByte) {
+        return { size, createTexture(size, nullptr, format, unit, type) };
     }
 
     void bindTexture(Texture&,
@@ -232,6 +238,8 @@ public:
     State<value::PixelTransferStencil> pixelTransferStencil;
 #endif // MBGL_USE_GLES2
 
+    bool supportsHalfFloatTextures = false;
+    
 private:
     State<value::StencilFunc> stencilFunc;
     State<value::StencilMask> stencilMask;
@@ -259,8 +267,8 @@ private:
     void updateVertexBuffer(UniqueBuffer& buffer, const void* data, std::size_t size);
     UniqueBuffer createIndexBuffer(const void* data, std::size_t size, const BufferUsage usage);
     void updateIndexBuffer(UniqueBuffer& buffer, const void* data, std::size_t size);
-    UniqueTexture createTexture(Size size, const void* data, TextureFormat, TextureUnit);
-    void updateTexture(TextureID, Size size, const void* data, TextureFormat, TextureUnit);
+    UniqueTexture createTexture(Size size, const void* data, TextureFormat, TextureUnit, TextureType);
+    void updateTexture(TextureID, Size size, const void* data, TextureFormat, TextureUnit, TextureType);
     UniqueFramebuffer createFramebuffer();
     UniqueRenderbuffer createRenderbuffer(RenderbufferType, Size size);
     std::unique_ptr<uint8_t[]> readFramebuffer(Size, TextureFormat, bool flip);
diff --git a/src/mbgl/gl/types.hpp b/src/mbgl/gl/types.hpp
index da08195e58..376a784a0c 100644
--- a/src/mbgl/gl/types.hpp
+++ b/src/mbgl/gl/types.hpp
@@ -64,6 +64,15 @@ enum class TextureFormat : uint32_t {
 #endif // MBGL_USE_GLES2
 };
 
+enum class TextureType : uint32_t {
+    UnsignedByte = 0x1401,
+#if MBGL_USE_GLES2
+    HalfFloat = 0x8D61,
+#else
+    HalfFloat = 0x140B,
+#endif // MBGL_USE_GLES2
+};
+
 enum class PrimitiveType {
     Points = 0x0000,
     Lines = 0x0001,