Merge of ~glmark2-dev/glmark2/shadow

Adds SceneShadow to exercise shadow mapping.

10 files changed, 630 insertions, 0 deletions

diff --git a/data/shaders/depth.frag b/data/shaders/depth.frag
new file mode 100644
index 0000000..e2a5256
--- /dev/null
+++ b/data/shaders/depth.frag
@@ -0,0 +1,6 @@
+varying vec3 Normal;
+
+void main()
+{
+    gl_FragColor = vec4(Normal, 1.0);
+}
diff --git a/data/shaders/depth.vert b/data/shaders/depth.vert
new file mode 100644
index 0000000..f424032
--- /dev/null
+++ b/data/shaders/depth.vert
@@ -0,0 +1,12 @@
+attribute vec3 position;
+attribute vec3 normal;
+
+uniform mat4 ModelViewProjectionMatrix;
+
+varying vec3 Normal;
+
+void main(void)
+{
+    Normal = normal;
+    gl_Position = ModelViewProjectionMatrix * vec4(position, 1.0);
+}
diff --git a/data/shaders/shadow.frag b/data/shaders/shadow.frag
new file mode 100644
index 0000000..6b86ace
--- /dev/null
+++ b/data/shaders/shadow.frag
@@ -0,0 +1,17 @@
+uniform sampler2D ShadowMap;
+
+varying vec4 Color;
+varying vec4 ShadowCoord;
+
+void main()
+{
+    vec4 sc_perspective = ShadowCoord / ShadowCoord.w;
+    sc_perspective.z += 0.1505;
+    vec4 shadow_value = texture2D(ShadowMap, sc_perspective.st);
+    float light_distance = shadow_value.z;
+    float shadow = 1.0;
+    if (ShadowCoord.w > 0.0 && light_distance < sc_perspective.z) {
+        shadow = 0.5;
+    }
+    gl_FragColor = vec4(shadow * Color.rgb, 1.0);
+}
diff --git a/data/shaders/shadow.vert b/data/shaders/shadow.vert
new file mode 100644
index 0000000..a8ba2b4
--- /dev/null
+++ b/data/shaders/shadow.vert
@@ -0,0 +1,16 @@
+attribute vec2 position;
+
+uniform mat4 LightMatrix;
+uniform mat4 ModelViewProjectionMatrix;
+
+varying vec4 ShadowCoord;
+varying vec4 Color;
+
+void main()
+{
+    Color = MaterialDiffuse;
+
+    vec4 pos4 = vec4(position, 0.0, 1.0);
+    ShadowCoord = LightMatrix * pos4;
+    gl_Position = ModelViewProjectionMatrix * pos4;
+}
diff --git a/src/android.cpp b/src/android.cpp
index d9678f4..53a17f7 100644
--- a/src/android.cpp
+++ b/src/android.cpp
@@ -275,6 +275,7 @@ create_and_add_scenes(std::vector<Scene*>& scenes, Canvas& canvas)
     scenes.push_back(new SceneIdeas(canvas));
     scenes.push_back(new SceneTerrain(canvas));
     scenes.push_back(new SceneJellyfish(canvas));
+    scenes.push_back(new SceneShadow(canvas));
 }
 
 
diff --git a/src/default-benchmarks.h b/src/default-benchmarks.h
index d121e30..45f7672 100644
--- a/src/default-benchmarks.h
+++ b/src/default-benchmarks.h
@@ -63,6 +63,7 @@ private:
         benchmarks.push_back("ideas:speed=duration");
         benchmarks.push_back("jellyfish");
         benchmarks.push_back("terrain");
+        benchmarks.push_back("shadow");
         benchmarks.push_back("conditionals:vertex-steps=0:fragment-steps=0");
         benchmarks.push_back("conditionals:vertex-steps=0:fragment-steps=5");
         benchmarks.push_back("conditionals:vertex-steps=5:fragment-steps=0");
diff --git a/src/main.cpp b/src/main.cpp
index 36cdf7b..d310a51 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -63,6 +63,7 @@ add_and_register_scenes(vector<Scene*>& scenes, Canvas& canvas)
     scenes.push_back(new SceneIdeas(canvas));
     scenes.push_back(new SceneTerrain(canvas));
     scenes.push_back(new SceneJellyfish(canvas));
+    scenes.push_back(new SceneShadow(canvas));
 
     for (vector<Scene*>::const_iterator iter = scenes.begin();
          iter != scenes.end();
diff --git a/src/mesh.cpp b/src/mesh.cpp
index bcc36e6..9ccbcc6 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -543,6 +543,8 @@ void
 Mesh::render_array()
 {
     for (size_t i = 0; i < vertex_format_.size(); i++) {
+        if (attrib_locations_[i] < 0)
+            continue;
         glEnableVertexAttribArray(attrib_locations_[i]);
         glVertexAttribPointer(attrib_locations_[i], vertex_format_[i].first,
                               GL_FLOAT, GL_FALSE, vertex_stride_,
@@ -552,6 +554,8 @@ Mesh::render_array()
     glDrawArrays(GL_TRIANGLES, 0, vertices_.size());
 
     for (size_t i = 0; i < vertex_format_.size(); i++) {
+        if (attrib_locations_[i] < 0)
+            continue;
         glDisableVertexAttribArray(attrib_locations_[i]);
     }
 }
@@ -566,6 +570,8 @@ void
 Mesh::render_vbo()
 {
     for (size_t i = 0; i < vertex_format_.size(); i++) {
+        if (attrib_locations_[i] < 0)
+            continue;
         glEnableVertexAttribArray(attrib_locations_[i]);
         glBindBuffer(GL_ARRAY_BUFFER, vbos_[i]);
         glVertexAttribPointer(attrib_locations_[i], vertex_format_[i].first,
@@ -576,6 +582,8 @@ Mesh::render_vbo()
     glDrawArrays(GL_TRIANGLES, 0, vertices_.size());
 
     for (size_t i = 0; i < vertex_format_.size(); i++) {
+        if (attrib_locations_[i] < 0)
+            continue;
         glDisableVertexAttribArray(attrib_locations_[i]);
     }
 }
diff --git a/src/scene-shadow.cpp b/src/scene-shadow.cpp
new file mode 100644
index 0000000..4fd27c7
--- /dev/null
+++ b/src/scene-shadow.cpp
@@ -0,0 +1,550 @@
+//
+// Copyright © 2012 Linaro Limited
+//
+// This file is part of the glmark2 OpenGL (ES) 2.0 benchmark.
+//
+// glmark2 is free software: you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation, either version 3 of the License, or (at your option) any later
+// version.
+//
+// glmark2 is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+// details.
+//
+// You should have received a copy of the GNU General Public License along with
+// glmark2.  If not, see <http://www.gnu.org/licenses/>.
+//
+// Authors:
+//  Jesse Barker
+//
+#include "scene.h"
+#include "model.h"
+#include "util.h"
+#include "log.h"
+#include "shader-source.h"
+#include "stack.h"
+
+using std::string;
+using std::vector;
+using std::map;
+using LibMatrix::Stack4;
+using LibMatrix::mat4;
+using LibMatrix::vec4;
+using LibMatrix::vec3;
+using LibMatrix::vec2;
+
+static const vec4 lightPosition(0.0f, 3.0f, 2.0f, 1.0f);
+
+//
+// To create a shadow map, we need a framebuffer object set up for a 
+// depth-only pass.  The render target can then be bound as a texture,
+// and the depth values sampled from that texture can be used in the
+// distance-from-light computations when rendering the shadow on the
+// ground below the rendered object.
+//
+class DepthRenderTarget
+{
+    Program program_;
+    unsigned int canvas_width_;
+    unsigned int canvas_height_;
+    unsigned int width_;
+    unsigned int height_;
+    unsigned int tex_;
+    unsigned int fbo_;
+public:
+    DepthRenderTarget() :
+        canvas_width_(0),
+        canvas_height_(0),
+        width_(0),
+        height_(0),
+        tex_(0),
+        fbo_(0) {}
+    ~DepthRenderTarget() {}
+    bool setup(unsigned int width, unsigned int height);
+    void teardown();
+    void enable(const mat4& mvp);
+    void disable();
+    unsigned int texture() { return tex_; }
+    Program& program() { return program_; }
+};
+
+bool
+DepthRenderTarget::setup(unsigned int width, unsigned int height)
+{
+    canvas_width_ = width;
+    canvas_height_ = height;
+    width_ = canvas_width_ * 2;
+    height_ = canvas_height_ * 2;
+
+    static const string vtx_shader_filename(GLMARK_DATA_PATH"/shaders/depth.vert");
+    static const string frg_shader_filename(GLMARK_DATA_PATH"/shaders/depth.frag");
+
+    ShaderSource vtx_source(vtx_shader_filename);
+    ShaderSource frg_source(frg_shader_filename);
+
+    if (!Scene::load_shaders_from_strings(program_, vtx_source.str(), frg_source.str())) {
+        return false;
+    }
+
+    glGenTextures(1, &tex_);
+    glBindTexture(GL_TEXTURE_2D, tex_);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, width_, height_, 0,
+                 GL_DEPTH_COMPONENT, GL_UNSIGNED_INT, 0);
+    glBindTexture(GL_TEXTURE_2D, 0);
+
+    glGenFramebuffers(1, &fbo_);
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo_);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D,
+                           tex_, 0);
+    unsigned int status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+    if (status != GL_FRAMEBUFFER_COMPLETE) {
+        Log::error("DepthRenderState::setup: glCheckFramebufferStatus failed (0x%x)\n", status);
+        return false;
+    }
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
+    return true;
+}
+
+void
+DepthRenderTarget::teardown()
+{
+    program_.stop();
+    program_.release();
+    if (tex_) {
+        glDeleteTextures(1, &tex_);
+        tex_ = 0;
+    }
+    if (fbo_) {
+        glDeleteFramebuffers(1, &fbo_);
+        fbo_ = 0;
+    }
+}
+
+void
+DepthRenderTarget::enable(const mat4& mvp)
+{
+    program_.start();
+    program_["ModelViewProjectionMatrix"] = mvp;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo_);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D,
+                           tex_, 0);
+    glViewport(0, 0, width_, height_);
+    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
+    glClear(GL_DEPTH_BUFFER_BIT);
+}
+
+void DepthRenderTarget::disable()
+{
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    glViewport(0, 0, canvas_width_, canvas_height_);
+    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+}
+
+//
+// The actual shadow pass is really just a quad projected into the scene
+// with the horse's shadow cast upon it.  In the vertex stage, we compute
+// a texture coordinate for the depth texture look-up by transforming the
+// current vertex position using a matrix describing the light's view point.
+// In the fragment stage, that coordinate is perspective corrected, and
+// used to sample the depth texture.  If the depth value for that fragment
+// (effectively the distance from the light to the object at that point)
+// is less than the Z component of that coordinate (effectively the distance
+// from the light to the ground at that point) then that location is in shadow.
+//
+class GroundRenderer
+{
+    Program program_;
+    mat4 light_;
+    Stack4 modelview_;
+    mat4 projection_;
+    int positionLocation_;
+    unsigned int bufferObject_;
+    unsigned int texture_;
+    vector<vec2> vertices_;
+    vector<vec2> texcoords_;
+    
+public:
+    GroundRenderer() :
+        positionLocation_(0),
+        bufferObject_(0) {}
+    ~GroundRenderer() {}
+    bool setup(const mat4& projection, unsigned int texture);
+    void teardown();
+    void draw();
+};
+
+bool
+GroundRenderer::setup(const mat4& projection, unsigned int texture)
+{
+    projection_ = projection;
+    texture_ = texture;
+
+    // Program set up
+    static const vec4 materialDiffuse(0.3f, 0.3f, 0.3f, 1.0f);
+    static const string vtx_shader_filename(GLMARK_DATA_PATH"/shaders/shadow.vert");
+    static const string frg_shader_filename(GLMARK_DATA_PATH"/shaders/shadow.frag");
+    ShaderSource vtx_source(vtx_shader_filename);
+    ShaderSource frg_source(frg_shader_filename);
+
+    vtx_source.add_const("MaterialDiffuse", materialDiffuse);
+
+    if (!Scene::load_shaders_from_strings(program_, vtx_source.str(), frg_source.str())) {
+        return false;
+    }
+    positionLocation_ = program_["position"].location();
+
+    // Set up the position data for our "quad".
+    vertices_.push_back(vec2(-1.0, -1.0));
+    vertices_.push_back(vec2(1.0, -1.0));
+    vertices_.push_back(vec2(-1.0, 1.0));
+    vertices_.push_back(vec2(1.0, 1.0));
+
+    // Set up the VBO and stash our position data in it.
+    glGenBuffers(1, &bufferObject_);
+    glBindBuffer(GL_ARRAY_BUFFER, bufferObject_);
+    glBufferData(GL_ARRAY_BUFFER, vertices_.size() * sizeof(vec2),
+                 &vertices_.front(), GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    // Set up the light matrix with a bias that will convert values
+    // in the range of [-1, 1] to [0, 1)], then add in the projection
+    // and the "look at" matrix from the light position.
+    light_ *= LibMatrix::Mat4::translate(0.5, 0.5, 0.5);
+    light_ *= LibMatrix::Mat4::scale(0.5, 0.5, 0.5);
+    light_ *= projection_;
+    light_ *= LibMatrix::Mat4::lookAt(lightPosition.x(), lightPosition.y(), lightPosition.z(),
+                                      0.0, 0.0, 0.0,
+                                      0.0, 1.0, 0.0);
+
+    return true;
+}
+
+void
+GroundRenderer::teardown()
+{
+    program_.stop();
+    program_.release();
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glDeleteBuffers(1, &bufferObject_);
+    bufferObject_ = 0;
+    texture_= 0;
+    vertices_.clear();
+}
+
+void
+GroundRenderer::draw()
+{
+    // Need to add uniforms for the shadow texture, and transformation to
+    // "lay the quad down".
+    modelview_.push();
+    modelview_.translate(projection_[0][3], projection_[1][3] - 0.8, projection_[2][3] - 0.5);
+    modelview_.rotate(-85.0, 1.0, 0.0, 0.0);
+    modelview_.scale(2.0, 2.0, 2.0);
+    mat4 mvp(projection_);
+    mvp *= modelview_.getCurrent();
+
+    glBindBuffer(GL_ARRAY_BUFFER, bufferObject_);
+    program_.start();
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_2D, texture_);
+    program_["ShadowMap"] = 0;
+    program_["LightMatrix"] = light_;
+    program_["ModelViewProjectionMatrix"] = mvp;
+
+    glEnableVertexAttribArray(positionLocation_);
+    glVertexAttribPointer(positionLocation_, 2, GL_FLOAT, GL_FALSE, 0, 0);
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+    glDisableVertexAttribArray(positionLocation_);
+    glBindTexture(GL_TEXTURE_2D, 0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    modelview_.pop();
+}
+
+class ShadowPrivate
+{
+    Canvas& canvas_;
+    DepthRenderTarget depthTarget_;
+    GroundRenderer ground_;
+    Program program_;
+    Stack4 modelview_;
+    Stack4 projection_;
+    Mesh mesh_;
+    vec3 centerVec_;
+    float radius_;
+    float rotation_;
+    float rotationSpeed_;
+    bool useVbo_;
+    
+public:
+    ShadowPrivate(Canvas& canvas) :
+        canvas_(canvas),
+        radius_(0.0),
+        rotation_(0.0),
+        rotationSpeed_(36.0),
+        useVbo_(true) {}
+    ~ShadowPrivate() {}
+
+    bool setup(map<string, Scene::Option>& options);
+    void teardown();
+    void update(double elapsedTime);
+    void draw();
+};
+
+bool
+ShadowPrivate::setup(map<string, Scene::Option>& options)
+{
+    // Program object setup
+    static const string vtx_shader_filename(GLMARK_DATA_PATH"/shaders/light-basic.vert");
+    static const string frg_shader_filename(GLMARK_DATA_PATH"/shaders/light-basic.frag");
+    static const vec4 materialDiffuse(1.0f, 1.0f, 1.0f, 1.0f);
+
+    ShaderSource vtx_source(vtx_shader_filename);
+    ShaderSource frg_source(frg_shader_filename);
+
+    vtx_source.add_const("LightSourcePosition", lightPosition);
+    vtx_source.add_const("MaterialDiffuse", materialDiffuse);
+
+    if (!Scene::load_shaders_from_strings(program_, vtx_source.str(), frg_source.str())) {
+        return false;
+    }
+
+    // Model setup
+    Model::find_models();
+    Model model;
+    bool modelLoaded = model.load("horse");
+
+    if(!modelLoaded) {
+        return false;
+    }
+
+    model.calculate_normals();
+
+    // Mesh setup
+    vector<std::pair<Model::AttribType, int> > attribs;
+    attribs.push_back(std::pair<Model::AttribType, int>(Model::AttribTypePosition, 3));
+    attribs.push_back(std::pair<Model::AttribType, int>(Model::AttribTypeNormal, 3));
+    model.convert_to_mesh(mesh_, attribs);
+
+    useVbo_ = (options["use-vbo"].value == "true");
+    bool interleave = (options["interleave"].value == "true");
+    mesh_.vbo_update_method(Mesh::VBOUpdateMethodMap);
+    mesh_.interleave(interleave);
+
+    if (useVbo_) {
+        mesh_.build_vbo();
+    }
+    else {
+        mesh_.build_array();
+    }
+
+    // Calculate a projection matrix that is a good fit for the model
+    vec3 maxVec = model.maxVec();
+    vec3 minVec = model.minVec();
+    vec3 diffVec = maxVec - minVec;
+    centerVec_ = maxVec + minVec;
+    centerVec_ /= 2.0;
+    float diameter = diffVec.length();
+    radius_ = diameter / 2;
+    float fovy = 2.0 * atanf(radius_ / (2.0 + radius_));
+    fovy /= M_PI;
+    fovy *= 180.0;
+    float aspect(static_cast<float>(canvas_.width())/static_cast<float>(canvas_.height()));
+    projection_.perspective(fovy, aspect, 2.0, 50.0);
+
+    if (!depthTarget_.setup(canvas_.width(), canvas_.height())) {
+        Log::error("Failed to set up the render target for the depth pass\n");
+        return false;
+    }
+
+    if (!ground_.setup(projection_.getCurrent(), depthTarget_.texture())) {
+        Log::error("Failed to set up the ground renderer\n");
+        return false;
+    }
+
+    return true;
+}
+
+
+void
+ShadowPrivate::teardown()
+{
+    depthTarget_.teardown();
+    ground_.teardown();
+    program_.stop();
+    program_.release();
+    mesh_.reset();
+}
+
+void
+ShadowPrivate::update(double elapsedTime)
+{
+    rotation_ = rotationSpeed_ * elapsedTime;
+}
+
+void
+ShadowPrivate::draw()
+{
+    // To perform the depth pass, set up the model-view transformation so
+    // that we're looking at the horse from the light position.  That will
+    // give us the appropriate view for the shadow.
+    modelview_.push();
+    modelview_.loadIdentity();
+    modelview_.lookAt(lightPosition.x(), lightPosition.y(), lightPosition.z(),
+                      0.0, 0.0, 0.0,
+                      0.0, 1.0, 0.0);
+    modelview_.rotate(rotation_, 0.0f, 1.0f, 0.0f);
+    mat4 mvp(projection_.getCurrent());
+    mvp *= modelview_.getCurrent();
+    modelview_.pop();
+
+    // Enable the depth render target with our transformation and render.
+    depthTarget_.enable(mvp);
+    vector<GLint> attrib_locations;
+    attrib_locations.push_back(depthTarget_.program()["position"].location());
+    attrib_locations.push_back(depthTarget_.program()["normal"].location());
+    mesh_.set_attrib_locations(attrib_locations);
+    if (useVbo_) {
+        mesh_.render_vbo();
+    }
+    else {
+        mesh_.render_array();
+    }
+    depthTarget_.disable();
+
+    // Ground rendering using the above generated texture...
+    ground_.draw();
+
+    // Draw the "normal" view of the horse
+    modelview_.push();
+    modelview_.translate(-centerVec_.x(), -centerVec_.y(), -(centerVec_.z() + 2.0 + radius_));
+    modelview_.rotate(rotation_, 0.0f, 1.0f, 0.0f);
+    mvp = projection_.getCurrent();
+    mvp *= modelview_.getCurrent();
+
+    program_.start();
+    program_["ModelViewProjectionMatrix"] = mvp;
+
+    // Load the NormalMatrix uniform in the shader. The NormalMatrix is the
+    // inverse transpose of the model view matrix.
+    LibMatrix::mat4 normal_matrix(modelview_.getCurrent());
+    normal_matrix.inverse().transpose();
+    program_["NormalMatrix"] = normal_matrix;
+    attrib_locations.clear();
+    attrib_locations.push_back(program_["position"].location());
+    attrib_locations.push_back(program_["normal"].location());
+    mesh_.set_attrib_locations(attrib_locations);
+    if (useVbo_) {
+        mesh_.render_vbo();
+    }
+    else {
+        mesh_.render_array();
+    }
+
+    // Per-frame cleanup
+    modelview_.pop();
+}
+
+SceneShadow::SceneShadow(Canvas& canvas) :
+    Scene(canvas, "shadow"),
+    priv_(0)
+{
+    options_["use-vbo"] = Scene::Option("use-vbo", "true",
+                                        "Whether to use VBOs for rendering",
+                                        "false,true");
+    options_["interleave"] = Scene::Option("interleave", "false",
+                                           "Whether to interleave vertex attribute data",
+                                           "false,true");
+}
+
+SceneShadow::~SceneShadow()
+{
+    delete priv_;
+}
+
+bool
+SceneShadow::supported(bool show_errors)
+{
+    static const string oes_depth_texture("GL_OES_depth_texture");
+    static const string arb_depth_texture("GL_ARB_depth_texture");
+    if (!GLExtensions::support(oes_depth_texture) &&
+        !GLExtensions::support(arb_depth_texture)) {
+        if (show_errors) {
+            Log::error("We do not have the depth texture extension!!!\n");
+        }
+
+        return false;
+    }
+    return true;
+}
+
+bool
+SceneShadow::load()
+{
+    running_ = false;
+    return true;
+}
+
+void
+SceneShadow::unload()
+{
+}
+
+bool
+SceneShadow::setup()
+{
+    // If the scene isn't supported, don't bother to go through setup.
+    if (!supported(false) || !Scene::setup())
+    {
+        return false;
+    }
+
+    priv_ = new ShadowPrivate(canvas_);
+    if (!priv_->setup(options_)) {
+        delete priv_;
+        priv_ = 0;
+        return false;
+    }
+
+    // Set core scene timing after actual initialization so we don't measure
+    // set up time.
+    startTime_ = Util::get_timestamp_us() / 1000000.0;
+    lastUpdateTime_ = startTime_;
+    running_ = true;
+
+    return true;
+}
+
+void
+SceneShadow::teardown()
+{
+    // Add scene-specific teardown here
+    priv_->teardown();
+    Scene::teardown();
+}
+
+void
+SceneShadow::update()
+{
+    Scene::update();
+    // Add scene-specific update here
+    priv_->update(lastUpdateTime_ - startTime_);
+}
+
+void
+SceneShadow::draw()
+{
+    priv_->draw();
+}
+
+Scene::ValidationResult
+SceneShadow::validate()
+{
+    return Scene::ValidationUnknown;
+}
diff --git a/src/scene.h b/src/scene.h
index a455fbd..dd77ba9 100644
--- a/src/scene.h
+++ b/src/scene.h
@@ -556,4 +556,22 @@ public:
     void draw();
     ValidationResult validate();
 };
+
+class ShadowPrivate;
+class SceneShadow : public Scene
+{
+    ShadowPrivate* priv_;
+public:
+    SceneShadow(Canvas& canvas);
+    ~SceneShadow();
+    bool supported(bool show_errors);
+    bool load();
+    void unload();
+    bool setup();
+    void teardown();
+    void update();
+    void draw();
+    ValidationResult validate();
+};
+
 #endif