Shaders: ability to render instanced object ID in Flat/Phong.

doc/changelog.dox

@@ -223,6 +223,8 @@ See also:
 -   Tangent space visualization in @ref Shaders::MeshVisualizer3D
 -   Texture coordinate transformation in @ref Shaders::DistanceFieldVector,
     @ref Shaders::Flat, @ref Shaders::Phong and @ref Shaders::Vector
+-   Ability to render Per-instance / per-vertex object ID in @ref Shaders::Flat
+    and @ref Shaders::Phong, in addition to uniform object ID
 -   New attribute definitions and an location allocation scheme in
     @ref Shaders::Generic --- @ref Shaders::Generic::Tangent4,
     @ref Shaders::Generic::Bitangent, @ref Shaders::Generic::ObjectId plus

src/Magnum/Shaders/Flat.cpp

@@ -69,6 +69,9 @@ template<UnsignedInt dimensions> Flat<dimensions>::Flat(const Flags flags): _fla
         .addSource(flags & Flag::VertexColor ? "#define VERTEX_COLOR\n" : "")
         .addSource(flags & Flag::TextureTransformation ? "#define TEXTURE_TRANSFORMATION\n" : "")
         .addSource(dimensions == 2 ? "#define TWO_DIMENSIONS\n" : "#define THREE_DIMENSIONS\n")
+        #ifndef MAGNUM_TARGET_GLES2
+        .addSource(flags >= Flag::InstancedObjectId ? "#define INSTANCED_OBJECT_ID\n" : "")
+        #endif
         .addSource(rs.get("generic.glsl"))
         .addSource(rs.get("Flat.vert"));
     frag.addSource(flags & Flag::Textured ? "#define TEXTURED\n" : "")
@@ -76,6 +79,7 @@ template<UnsignedInt dimensions> Flat<dimensions>::Flat(const Flags flags): _fla
         .addSource(flags & Flag::VertexColor ? "#define VERTEX_COLOR\n" : "")
         #ifndef MAGNUM_TARGET_GLES2
         .addSource(flags & Flag::ObjectId ? "#define OBJECT_ID\n" : "")
+        .addSource(flags >= Flag::InstancedObjectId ? "#define INSTANCED_OBJECT_ID\n" : "")
         #endif
         .addSource(rs.get("generic.glsl"))
         .addSource(rs.get("Flat.frag"));
@@ -101,6 +105,8 @@ template<UnsignedInt dimensions> Flat<dimensions>::Flat(const Flags flags): _fla
             bindFragmentDataLocation(ColorOutput, "color");
             bindFragmentDataLocation(ObjectIdOutput, "objectId");
         }
+        if(flags >= Flag::InstancedObjectId)
+            bindAttributeLocation(ObjectId::Location, "instanceObjectId");
         #endif
     }
     #endif
@@ -195,6 +201,7 @@ Debug& operator<<(Debug& debug, const FlatFlag value) {
         _c(TextureTransformation)
         #ifndef MAGNUM_TARGET_GLES2
         _c(ObjectId)
+        _c(InstancedObjectId)
         #endif
         #undef _c
         /* LCOV_EXCL_STOP */
@@ -210,6 +217,7 @@ Debug& operator<<(Debug& debug, const FlatFlags value) {
         FlatFlag::VertexColor,
         FlatFlag::TextureTransformation,
         #ifndef MAGNUM_TARGET_GLES2
+        FlatFlag::InstancedObjectId, /* Superset of ObjectId */
         FlatFlag::ObjectId
         #endif
         });

src/Magnum/Shaders/Flat.frag

@@ -72,6 +72,10 @@ in mediump vec2 interpolatedTextureCoordinates;
 in lowp vec4 interpolatedVertexColor;
 #endif
 
+#ifdef INSTANCED_OBJECT_ID
+flat in highp uint interpolatedInstanceObjectId;
+#endif
+
 #ifdef NEW_GLSL
 #ifdef EXPLICIT_ATTRIB_LOCATION
 layout(location = COLOR_OUTPUT_ATTRIBUTE_LOCATION)
@@ -104,6 +108,10 @@ void main() {
     #endif
 
     #ifdef OBJECT_ID
-    fragmentObjectId = objectId;
+    fragmentObjectId =
+        #ifdef INSTANCED_OBJECT_ID
+        interpolatedInstanceObjectId +
+        #endif
+        objectId;
     #endif
 }

src/Magnum/Shaders/Flat.h

@@ -43,7 +43,8 @@ namespace Implementation {
         VertexColor = 1 << 2,
         TextureTransformation = 1 << 3,
         #ifndef MAGNUM_TARGET_GLES2
-        ObjectId = 1 << 4
+        ObjectId = 1 << 4,
+        InstancedObjectId = (1 << 5)|ObjectId
         #endif
     };
     typedef Containers::EnumSet<FlatFlag> FlatFlags;
@@ -115,6 +116,11 @@ on framebuffers with integer attachments.
 
 @snippet MagnumShaders.cpp Flat-usage-object-id
 
+If you have a batch of meshes with different object IDs, enable
+@ref Flag::InstancedObjectId and supply per-vertex IDs to the @ref ObjectId
+attribute. The output will contain a sum of the per-vertex ID and ID coming
+from @ref setObjectId().
+
 @requires_gles30 Object ID output requires integer buffer attachments, which
     are not available in OpenGL ES 2.0 or WebGL 1.0.
 
@@ -160,6 +166,20 @@ template<UnsignedInt dimensions> class MAGNUM_SHADERS_EXPORT Flat: public GL::Ab
          */
         typedef typename Generic<dimensions>::Color4 Color4;
 
+        #ifndef MAGNUM_TARGET_GLES2
+        /**
+         * @brief (Instanced) object ID
+         * @m_since_latest
+         *
+         * @ref shaders-generic "Generic attribute", @ref Magnum::UnsignedInt.
+         * Used only if @ref Flag::InstancedObjectId is set.
+         * @requires_gles30 Object ID output requires integer buffer
+         *      attachments, which are not available in OpenGL ES 2.0 or WebGL
+         *      1.0.
+         */
+        typedef typename Generic<dimensions>::ObjectId ObjectId;
+        #endif
+
         enum: UnsignedInt {
             /**
              * Color shader output. Present always, expects three- or
@@ -234,7 +254,20 @@ template<UnsignedInt dimensions> class MAGNUM_SHADERS_EXPORT Flat: public GL::Ab
              *      WebGL 1.0.
              * @m_since{2019,10}
              */
-            ObjectId = 1 << 4
+            ObjectId = 1 << 4,
+
+            /**
+             * Instanced object ID. Retrieves a per-instance / per-vertex
+             * object ID from the @ref ObjectId attribute, outputting a sum of
+             * the per-vertex ID and ID coming from @ref setObjectId().
+             * Implicitly enables @ref Flag::ObjectId. See
+             * @ref Shaders-Flat-usage-object-id for more information.
+             * @requires_gles30 Object ID output requires integer buffer
+             *      attachments, which are not available in OpenGL ES 2.0 or
+             *      WebGL 1.0.
+             * @m_since_latest
+             */
+            InstancedObjectId = (1 << 5)|ObjectId
             #endif
         };
 
@@ -346,7 +379,8 @@ template<UnsignedInt dimensions> class MAGNUM_SHADERS_EXPORT Flat: public GL::Ab
          * Expects that the shader was created with @ref Flag::ObjectId
          * enabled. Value set here is written to the @ref ObjectIdOutput, see
          * @ref Shaders-Flat-usage-object-id for more information. Default is
-         * @cpp 0 @ce.
+         * @cpp 0 @ce. If @ref Flag::InstancedObjectId is enabled as well, this
+         * value is combined with ID coming from the @ref ObjectId attribute.
          * @requires_gles30 Object ID output requires integer buffer
          *      attachments, which are not available in OpenGL ES 2.0 or WebGL
          *      1.0.

src/Magnum/Shaders/Flat.vert

@@ -87,6 +87,15 @@ in lowp vec4 vertexColor;
 out lowp vec4 interpolatedVertexColor;
 #endif
 
+#ifdef INSTANCED_OBJECT_ID
+#ifdef EXPLICIT_ATTRIB_LOCATION
+layout(location = OBJECT_ID_ATTRIBUTE_LOCATION)
+#endif
+in highp uint instanceObjectId;
+
+flat out highp uint interpolatedInstanceObjectId;
+#endif
+
 void main() {
     #ifdef TWO_DIMENSIONS
     gl_Position.xywz = vec4(transformationProjectionMatrix*vec3(position, 1.0), 0.0);
@@ -111,4 +120,9 @@ void main() {
     /* Vertex colors, if enabled */
     interpolatedVertexColor = vertexColor;
     #endif
+
+    #ifdef INSTANCED_OBJECT_ID
+    /* Instanced object ID, if enabled */
+    interpolatedInstanceObjectId = instanceObjectId;
+    #endif
 }

src/Magnum/Shaders/Phong.cpp

@@ -101,6 +101,9 @@ Phong::Phong(const Flags flags, const UnsignedInt lightCount): _flags{flags}, _l
         .addSource(flags & Flag::VertexColor ? "#define VERTEX_COLOR\n" : "")
         .addSource(flags & Flag::TextureTransformation ? "#define TEXTURE_TRANSFORMATION\n" : "")
         .addSource(Utility::formatString("#define LIGHT_COUNT {}\n", lightCount))
+        #ifndef MAGNUM_TARGET_GLES2
+        .addSource(flags >= Flag::InstancedObjectId ? "#define INSTANCED_OBJECT_ID\n" : "")
+        #endif
         .addSource(rs.get("generic.glsl"))
         .addSource(rs.get("Phong.vert"));
     frag.addSource(flags & Flag::AmbientTexture ? "#define AMBIENT_TEXTURE\n" : "")
@@ -111,6 +114,7 @@ Phong::Phong(const Flags flags, const UnsignedInt lightCount): _flags{flags}, _l
         .addSource(flags & Flag::AlphaMask ? "#define ALPHA_MASK\n" : "")
         #ifndef MAGNUM_TARGET_GLES2
         .addSource(flags & Flag::ObjectId ? "#define OBJECT_ID\n" : "")
+        .addSource(flags >= Flag::InstancedObjectId ? "#define INSTANCED_OBJECT_ID\n" : "")
         #endif
         .addSource(Utility::formatString(
             "#define LIGHT_COUNT {}\n"
@@ -146,6 +150,8 @@ Phong::Phong(const Flags flags, const UnsignedInt lightCount): _flags{flags}, _l
             bindFragmentDataLocation(ColorOutput, "color");
             bindFragmentDataLocation(ObjectIdOutput, "objectId");
         }
+        if(flags >= Flag::InstancedObjectId)
+            bindAttributeLocation(ObjectId::Location, "instanceObjectId");
         #endif
     }
     #endif
@@ -355,6 +361,7 @@ Debug& operator<<(Debug& debug, const Phong::Flag value) {
         _c(VertexColor)
         _c(TextureTransformation)
         #ifndef MAGNUM_TARGET_GLES2
+        _c(InstancedObjectId)
         _c(ObjectId)
         #endif
         #undef _c
@@ -374,6 +381,7 @@ Debug& operator<<(Debug& debug, const Phong::Flags value) {
         Phong::Flag::VertexColor,
         Phong::Flag::TextureTransformation,
         #ifndef MAGNUM_TARGET_GLES2
+        Phong::Flag::InstancedObjectId, /* Superset of ObjectId */
         Phong::Flag::ObjectId
         #endif
         });

src/Magnum/Shaders/Phong.frag

@@ -153,6 +153,10 @@ in mediump vec2 interpolatedTextureCoordinates;
 in lowp vec4 interpolatedVertexColor;
 #endif
 
+#ifdef INSTANCED_OBJECT_ID
+flat in highp uint interpolatedInstanceObjectId;
+#endif
+
 #ifdef NEW_GLSL
 #ifdef EXPLICIT_ATTRIB_LOCATION
 layout(location = COLOR_OUTPUT_ATTRIBUTE_LOCATION)
@@ -229,6 +233,10 @@ void main() {
     #endif
 
     #ifdef OBJECT_ID
-    fragmentObjectId = objectId;
+    fragmentObjectId =
+        #ifdef INSTANCED_OBJECT_ID
+        interpolatedInstanceObjectId +
+        #endif
+        objectId;
     #endif
 }

src/Magnum/Shaders/Phong.h

@@ -98,10 +98,14 @@ diffuse part and then separate the alpha like this:
 
 The shader supports writing object ID to the framebuffer for object picking or
 other annotation purposes. Enable it using @ref Flag::ObjectId and set up an
-integer buffer attached to the @ref ObjectIdOutput attachment. The
-functionality is practically the same as in the @ref Flat shader, see its
-@ref Shaders-Flat-usage-object-id documentation for more information and usage
-example.
+integer buffer attached to the @ref ObjectIdOutput attachment. If you have a
+batch of meshes with different object IDs, enable @ref Flag::InstancedObjectId
+and supply per-vertex IDs to the @ref ObjectId attribute. The output will
+contain a sum of the per-vertex ID and ID coming from @ref setObjectId().
+
+The functionality is practically the same as in the @ref Flat shader, see
+@ref Shaders-Flat-usage-object-id "its documentation" for more information and
+usage example.
 
 @requires_gles30 Object ID output requires integer buffer attachments, which
     are not available in OpenGL ES 2.0 or WebGL 1.0.
@@ -175,6 +179,20 @@ class MAGNUM_SHADERS_EXPORT Phong: public GL::AbstractShaderProgram {
          */
         typedef Generic3D::Color4 Color4;
 
+        #ifndef MAGNUM_TARGET_GLES2
+        /**
+         * @brief (Instanced) object ID
+         * @m_since_latest
+         *
+         * @ref shaders-generic "Generic attribute", @ref Magnum::UnsignedInt.
+         * Used only if @ref Flag::InstancedObjectId is set.
+         * @requires_gles30 Object ID output requires integer buffer
+         *      attachments, which are not available in OpenGL ES 2.0 or WebGL
+         *      1.0.
+         */
+        typedef Generic3D::ObjectId ObjectId;
+        #endif
+
         enum: UnsignedInt {
             /**
              * Color shader output. @ref shaders-generic "Generic output",
@@ -205,7 +223,7 @@ class MAGNUM_SHADERS_EXPORT Phong: public GL::AbstractShaderProgram {
          *
          * @see @ref Flags, @ref flags()
          */
-        enum class Flag: UnsignedByte {
+        enum class Flag: UnsignedShort {
             /**
              * Multiply ambient color with a texture.
              * @see @ref setAmbientColor(), @ref bindAmbientTexture()
@@ -271,7 +289,20 @@ class MAGNUM_SHADERS_EXPORT Phong: public GL::AbstractShaderProgram {
              *      WebGL 1.0.
              * @m_since{2019,10}
              */
-            ObjectId = 1 << 7
+            ObjectId = 1 << 7,
+
+            /**
+             * Instanced object ID. Retrieves a per-instance / per-vertex
+             * object ID from the @ref ObjectId attribute, outputting a sum of
+             * the per-vertex ID and ID coming from @ref setObjectId().
+             * Implicitly enables @ref Flag::ObjectId. See
+             * @ref Shaders-Phong-usage-object-id for more information.
+             * @requires_gles30 Object ID output requires integer buffer
+             *      attachments, which are not available in OpenGL ES 2.0 or
+             *      WebGL 1.0.
+             * @m_since_latest
+             */
+            InstancedObjectId = (1 << 8)|ObjectId
             #endif
         };
 

src/Magnum/Shaders/Phong.vert

@@ -113,6 +113,15 @@ in lowp vec4 vertexColor;
 out lowp vec4 interpolatedVertexColor;
 #endif
 
+#ifdef INSTANCED_OBJECT_ID
+#ifdef EXPLICIT_ATTRIB_LOCATION
+layout(location = OBJECT_ID_ATTRIBUTE_LOCATION)
+#endif
+in highp uint instanceObjectId;
+
+flat out highp uint interpolatedInstanceObjectId;
+#endif
+
 #if LIGHT_COUNT
 out mediump vec3 transformedNormal;
 #ifdef NORMAL_TEXTURE
@@ -160,4 +169,9 @@ void main() {
     /* Vertex colors, if enabled */
     interpolatedVertexColor = vertexColor;
     #endif
+
+    #ifdef INSTANCED_OBJECT_ID
+    /* Instanced object ID, if enabled */
+    interpolatedInstanceObjectId = instanceObjectId;
+    #endif
 }

src/Magnum/Shaders/Test/FlatGLTest.cpp

@@ -143,6 +143,7 @@ constexpr struct {
     {"vertex colors + textured", Flat2D::Flag::VertexColor|Flat2D::Flag::Textured},
     #ifndef MAGNUM_TARGET_GLES2
     {"object ID", Flat2D::Flag::ObjectId},
+    {"instanced object ID", Flat2D::Flag::InstancedObjectId},
     {"object ID + alpha mask + textured", Flat2D::Flag::ObjectId|Flat2D::Flag::AlphaMask|Flat2D::Flag::Textured}
     #endif
 };
@@ -182,6 +183,23 @@ const struct {
         Flat2D::Flag::Textured|Flat2D::Flag::AlphaMask, 1.0f}
 };
 
+#ifndef MAGNUM_TARGET_GLES2
+constexpr struct {
+    const char* name;
+    Flat2D::Flags flags;
+    UnsignedInt uniformId;
+    UnsignedInt instanceCount;
+    UnsignedInt expected;
+} RenderObjectIdData[] {
+    {"", /* Verify that it can hold 16 bits at least */
+        Flat2D::Flag::ObjectId, 48526, 0, 48526},
+    {"instanced, first instance",
+        Flat2D::Flag::InstancedObjectId, 13524, 1, 24526},
+    {"instanced, second instance",
+        Flat2D::Flag::InstancedObjectId, 13524, 2, 62347}
+};
+#endif
+
 FlatGLTest::FlatGLTest() {
     addInstancedTests<FlatGLTest>({
         &FlatGLTest::construct<2>,
@@ -236,8 +254,9 @@ FlatGLTest::FlatGLTest() {
         &FlatGLTest::renderAlphaTeardown);
 
     #ifndef MAGNUM_TARGET_GLES2
-    addTests({&FlatGLTest::renderObjectId2D,
-              &FlatGLTest::renderObjectId3D},
+    addInstancedTests({&FlatGLTest::renderObjectId2D,
+                       &FlatGLTest::renderObjectId3D},
+        Containers::arraySize(RenderObjectIdData),
         &FlatGLTest::renderObjectIdSetup,
         &FlatGLTest::renderObjectIdTeardown);
     #endif
@@ -975,14 +994,23 @@ void FlatGLTest::renderObjectIdTeardown() {
 }
 
 void FlatGLTest::renderObjectId2D() {
+    auto&& data = RenderObjectIdData[testCaseInstanceId()];
+    setTestCaseDescription(data.name);
+
     CORRADE_COMPARE(_framebuffer.checkStatus(GL::FramebufferTarget::Draw), GL::Framebuffer::Status::Complete);
 
     GL::Mesh circle = MeshTools::compile(Primitives::circle2DSolid(32));
 
-    Flat2D{Flat3D::Flag::ObjectId}
+    if(data.instanceCount) circle
+        .setInstanceCount(data.instanceCount)
+        .addVertexBufferInstanced(
+            GL::Buffer{Containers::arrayView({11002u, 48823u})},
+            1, 0, Flat2D::ObjectId{});
+
+    Flat2D{data.flags}
         .setColor(0x9999ff_rgbf)
         .setTransformationProjectionMatrix(Matrix3::projection({2.1f, 2.1f}))
-        .setObjectId(47523)
+        .setObjectId(data.uniformId)
         .draw(circle);
 
     MAGNUM_VERIFY_NO_GL_ERROR();
@@ -1014,23 +1042,32 @@ void FlatGLTest::renderObjectId2D() {
     MAGNUM_VERIFY_NO_GL_ERROR();
     /* Outside of the object, cleared to 27 */
     CORRADE_COMPARE(image.pixels<UnsignedInt>()[10][10], 27);
-    /* Inside of the object. Verify that it can hold 16 bits at least. */
-    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], 47523);
+    /* Inside of the object */
+    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], data.expected);
 }
 
 void FlatGLTest::renderObjectId3D() {
+    auto&& data = RenderObjectIdData[testCaseInstanceId()];
+    setTestCaseDescription(data.name);
+
     CORRADE_COMPARE(_framebuffer.checkStatus(GL::FramebufferTarget::Draw), GL::Framebuffer::Status::Complete);
 
     GL::Mesh sphere = MeshTools::compile(Primitives::uvSphereSolid(16, 32));
 
-    Flat3D{Flat3D::Flag::ObjectId}
+    if(data.instanceCount) sphere
+        .setInstanceCount(data.instanceCount)
+        .addVertexBufferInstanced(
+            GL::Buffer{Containers::arrayView({11002u, 48823u})},
+            1, 0, Flat2D::ObjectId{});
+
+    Flat3D{data.flags}
         .setColor(0x9999ff_rgbf)
         .setTransformationProjectionMatrix(
             Matrix4::perspectiveProjection(60.0_degf, 1.0f, 0.1f, 10.0f)*
             Matrix4::translation(Vector3::zAxis(-2.15f))*
             Matrix4::rotationY(-15.0_degf)*
             Matrix4::rotationX(15.0_degf))
-        .setObjectId(48526)
+        .setObjectId(data.uniformId)
         .draw(sphere);
 
     MAGNUM_VERIFY_NO_GL_ERROR();
@@ -1065,8 +1102,8 @@ void FlatGLTest::renderObjectId3D() {
     MAGNUM_VERIFY_NO_GL_ERROR();
     /* Outside of the object, cleared to 27 */
     CORRADE_COMPARE(image.pixels<UnsignedInt>()[10][10], 27);
-    /* Inside of the object. Verify that it can hold 16 bits at least. */
-    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], 48526);
+    /* Inside of the object */
+    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], data.expected);
 }
 #endif
 

src/Magnum/Shaders/Test/FlatTest.cpp

@@ -39,6 +39,9 @@ struct FlatTest: TestSuite::Tester {
 
     void debugFlag();
     void debugFlags();
+    #ifndef MAGNUM_TARGET_GLES2
+    void debugFlagsInstancedObjectId();
+    #endif
 };
 
 FlatTest::FlatTest() {
@@ -49,7 +52,11 @@ FlatTest::FlatTest() {
               &FlatTest::constructCopy<3>,
 
               &FlatTest::debugFlag,
-              &FlatTest::debugFlags});
+              &FlatTest::debugFlags,
+              #ifndef MAGNUM_TARGET_GLES2
+              &FlatTest::debugFlagsInstancedObjectId
+              #endif
+              });
 }
 
 template<UnsignedInt dimensions> void FlatTest::constructNoCreate() {
@@ -87,6 +94,17 @@ void FlatTest::debugFlags() {
     CORRADE_COMPARE(out.str(), "Shaders::Flat::Flag::Textured|Shaders::Flat::Flag::AlphaMask Shaders::Flat::Flags{}\n");
 }
 
+#ifndef MAGNUM_TARGET_GLES2
+void FlatTest::debugFlagsInstancedObjectId() {
+    std::ostringstream out;
+
+    /* InstancedObjectId is a superset of ObjectId so only one should be
+     *printed */
+    Debug{&out} << (Flat3D::Flag::ObjectId|Flat3D::Flag::InstancedObjectId);
+    CORRADE_COMPARE(out.str(), "Shaders::Flat::Flag::InstancedObjectId\n");
+}
+#endif
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::Shaders::Test::FlatTest)

src/Magnum/Shaders/Test/PhongGLTest.cpp

@@ -151,6 +151,7 @@ constexpr struct {
     {"vertex colors + diffuse texture", Phong::Flag::VertexColor|Phong::Flag::DiffuseTexture, 1},
     #ifndef MAGNUM_TARGET_GLES2
     {"object ID", Phong::Flag::ObjectId, 1},
+    {"instanced object ID", Phong::Flag::InstancedObjectId, 1},
     {"object ID + alpha mask + specular texture", Phong::Flag::ObjectId|Phong::Flag::AlphaMask|Phong::Flag::SpecularTexture, 1},
     #endif
     {"five lights", {}, 5},
@@ -266,6 +267,23 @@ const struct {
         0xffffffff_rgbaf, 0x9999ff00_rgbaf}
 };
 
+#ifndef MAGNUM_TARGET_GLES2
+constexpr struct {
+    const char* name;
+    Phong::Flags flags;
+    UnsignedInt uniformId;
+    UnsignedInt instanceCount;
+    UnsignedInt expected;
+} RenderObjectIdData[] {
+    {"", /* Verify that it can hold 16 bits at least */
+        Phong::Flag::ObjectId, 48526, 0, 48526},
+    {"instanced, first instance",
+        Phong::Flag::InstancedObjectId, 13524, 1, 24526},
+    {"instanced, second instance",
+        Phong::Flag::InstancedObjectId, 13524, 2, 62347}
+};
+#endif
+
 PhongGLTest::PhongGLTest() {
     addInstancedTests({&PhongGLTest::construct}, Containers::arraySize(ConstructData));
 
@@ -322,7 +340,8 @@ PhongGLTest::PhongGLTest() {
         &PhongGLTest::renderAlphaTeardown);
 
     #ifndef MAGNUM_TARGET_GLES2
-    addTests({&PhongGLTest::renderObjectId},
+    addInstancedTests({&PhongGLTest::renderObjectId},
+        Containers::arraySize(RenderObjectIdData),
         &PhongGLTest::renderObjectIdSetup,
         &PhongGLTest::renderObjectIdTeardown);
     #endif
@@ -1158,11 +1177,20 @@ void PhongGLTest::renderObjectIdTeardown() {
 }
 
 void PhongGLTest::renderObjectId() {
+    auto&& data = RenderObjectIdData[testCaseInstanceId()];
+    setTestCaseDescription(data.name);
+
     CORRADE_COMPARE(_framebuffer.checkStatus(GL::FramebufferTarget::Draw), GL::Framebuffer::Status::Complete);
 
     GL::Mesh sphere = MeshTools::compile(Primitives::uvSphereSolid(16, 32));
 
-    Phong{Phong::Flag::ObjectId, 2}
+    if(data.instanceCount) sphere
+        .setInstanceCount(data.instanceCount)
+        .addVertexBufferInstanced(
+            GL::Buffer{Containers::arrayView({11002u, 48823u})},
+            1, 0, Phong::ObjectId{});
+
+    Phong{data.flags, 2}
         .setLightColors({0x993366_rgbf, 0x669933_rgbf})
         .setLightPositions({{-3.0f, -3.0f, 0.0f},
                             { 3.0f, -3.0f, 0.0f}})
@@ -1171,7 +1199,7 @@ void PhongGLTest::renderObjectId() {
         .setSpecularColor(0x6666ff_rgbf)
         .setTransformationMatrix(Matrix4::translation(Vector3::zAxis(-2.15f)))
         .setProjectionMatrix(Matrix4::perspectiveProjection(60.0_degf, 1.0f, 0.1f, 10.0f))
-        .setObjectId(48526)
+        .setObjectId(data.uniformId)
         .draw(sphere);
 
     MAGNUM_VERIFY_NO_GL_ERROR();
@@ -1205,8 +1233,8 @@ void PhongGLTest::renderObjectId() {
     MAGNUM_VERIFY_NO_GL_ERROR();
     /* Outside of the object, cleared to 27 */
     CORRADE_COMPARE(image.pixels<UnsignedInt>()[10][10], 27);
-    /* Inside of the object. Verify that it can hold 16 bits at least. */
-    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], 48526);
+    /* Inside of the object */
+    CORRADE_COMPARE(image.pixels<UnsignedInt>()[40][46], data.expected);
 }
 #endif
 

src/Magnum/Shaders/Test/PhongTest.cpp

@@ -39,6 +39,9 @@ struct PhongTest: TestSuite::Tester {
 
     void debugFlag();
     void debugFlags();
+    #ifndef MAGNUM_TARGET_GLES2
+    void debugFlagsInstancedObjectId();
+    #endif
 };
 
 PhongTest::PhongTest() {
@@ -46,7 +49,11 @@ PhongTest::PhongTest() {
               &PhongTest::constructCopy,
 
               &PhongTest::debugFlag,
-              &PhongTest::debugFlags});
+              &PhongTest::debugFlags,
+              #ifndef MAGNUM_TARGET_GLES2
+              &PhongTest::debugFlagsInstancedObjectId
+              #endif
+              });
 }
 
 void PhongTest::constructNoCreate() {
@@ -77,6 +84,17 @@ void PhongTest::debugFlags() {
     CORRADE_COMPARE(out.str(), "Shaders::Phong::Flag::DiffuseTexture|Shaders::Phong::Flag::SpecularTexture Shaders::Phong::Flags{}\n");
 }
 
+#ifndef MAGNUM_TARGET_GLES2
+void PhongTest::debugFlagsInstancedObjectId() {
+    std::ostringstream out;
+
+    /* InstancedObjectId is a superset of ObjectId so only one should be
+     *printed */
+    Debug{&out} << (Phong::Flag::ObjectId|Phong::Flag::InstancedObjectId);
+    CORRADE_COMPARE(out.str(), "Shaders::Phong::Flag::InstancedObjectId\n");
+}
+#endif
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::Shaders::Test::PhongTest)