Add missing NaCl PPAPI test components to Chrome repo.

ppapi/native_client/tests/earth/earth.cc

+/*
+ * Copyright (c) 2011 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+// NaCl Earth demo
+// Ray trace planet Earth
+
+#include "native_client/tests/earth/earth.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <math.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define HAVE_THREADS 1
+#include "native_client/common/worker.h"
+
+// print/debug messages
+static void InfoPrintf(const char *fmt, ...) {
+  va_list argptr;
+  va_start (argptr, fmt);
+  vfprintf (stderr, fmt, argptr);
+  va_end (argptr);
+  fflush(stderr);
+}
+
+extern "C" void DebugPrintf(const char *fmt, ...) {
+  va_list argptr;
+  fprintf (stderr, "@@@ EARTH ");
+
+  va_start (argptr, fmt);
+  vfprintf (stderr, fmt, argptr);
+  va_end (argptr);
+  fflush(stderr);
+}
+
+// global properties
+const float kPI = M_PI;
+const float kOneOverPI = 1.0f / kPI;
+const float kOneOver2PI = 1.0f / (2.0f * kPI);
+const float kOneOver255 = 1.0f / 255.0f;
+const int kArcCosineTableSize = 4096;
+const float kMaxWindow = 4096;
+const int kEarthTextureWidth = 1024;
+const int kEarthTextureHeight = 512;
+const int kMaxFrames = 1000000;
+const int kRegionRatio = 8;
+int g_window_width = 512;
+int g_window_height = 512;
+int g_num_frames = 300;
+bool g_ask_sysconf = true;
+int g_num_threads = 4;           // possibly overridden by sysconf()
+int g_num_regions = 4;           // possibly overridden by sysconf()
+bool g_multi_threading = false;  // can be overridden on cmd line
+
+int g_frame_checksum = 0; // used for nacl module testing
+
+// seed for rand_r() - we only call rand_r from main thread.
+static unsigned int g_seed = 0xC0DE533D;
+
+// random number helper
+inline unsigned char rand255() {
+  return static_cast<unsigned char>(rand_r(&g_seed) & 255);
+}
+
+// random number helper
+inline float frand() {
+  return (static_cast<float>(rand_r(&g_seed)) / static_cast<float>(RAND_MAX));
+}
+
+// build a packed color
+inline uint32_t MakeRGBA(uint32_t r, uint32_t g, uint32_t b, uint32_t a) {
+  return (((a) << 24) | ((r) << 16) | ((g) << 8) | (b));
+}
+
+// extraction routines
+inline float ExtractR(uint32_t c) {
+  return static_cast<float>(c & 0xFF) * kOneOver255;
+}
+
+inline float ExtractG(uint32_t c) {
+  return static_cast<float>((c & 0xFF00) >> 8) * kOneOver255;
+}
+
+inline float ExtractB(uint32_t c) {
+  return static_cast<float>((c & 0xFF0000) >> 16) * kOneOver255;
+}
+
+
+// simple container for earth texture
+struct Texture {
+  int width, height;
+  unsigned int pixels[kEarthTextureWidth * kEarthTextureHeight];
+};
+
+
+// compile our texture straight in to avoid runtime filesystem
+Texture g_earth = {
+  kEarthTextureWidth, kEarthTextureHeight, {
+#include "native_client/tests/earth/earth_image.inc"
+  }
+};
+
+
+struct Surface {
+  int width, height, pitch;
+  uint32_t *pixels;
+  Surface(uint32_t *pix, int w, int h) {
+    width = w;
+    height = h;
+    pitch = w;
+    pixels = pix;
+  }
+};
+
+
+struct ArcCosine {
+  // slightly larger table so we can interpolate beyond table size
+  float table[kArcCosineTableSize + 2];
+  float TableLerp(float x);
+  ArcCosine();
+  ~ArcCosine() { ; }
+};
+
+
+ArcCosine::ArcCosine() {
+  // build a slightly larger table to allow for numeric imprecision
+  for (int i = 0; i < (kArcCosineTableSize + 2); ++i) {
+    float f = static_cast<float>(i) / kArcCosineTableSize;
+    f = f * 2.0f - 1.0f;
+    table[i] = acos(f);
+  }
+}
+
+
+// looks up acos(f) using a table and lerping between entries
+// (it is expected that input f is between -1 and 1)
+float ArcCosine::TableLerp(float f) {
+  float x = (f + 1.0f) * 0.5f;
+  x = x * kArcCosineTableSize;
+  int ix = static_cast<int>(x);
+  float fx = static_cast<float>(ix);
+  float dx = x - fx;
+  float af = table[ix];
+  float af2 = table[ix + 1];
+  float a = af + (af2 - af) * dx;
+  return a;
+}
+
+
+// takes a -0..1+ color, clamps it to 0..1 and maps it to 0..255 integer
+inline unsigned int Clamp255(float x) {
+  if (x < 0.0f) {
+    x = 0.0f;
+  } else if (x > 1.0f) {
+    x = 1.0f;
+  }
+  return (unsigned int)(x * 255.0f);
+}
+
+
+// Planet class holds information and functionality needed to render
+// a ray-traced planet into an raw pixel surface
+class Planet {
+  float planet_radius_;
+  float planet_spin_;
+  float planet_x_, planet_y_, planet_z_;
+  float planet_pole_x_, planet_pole_y_, planet_pole_z_;
+  float planet_equator_x_, planet_equator_y_, planet_equator_z_;
+  float eye_x_, eye_y_, eye_z_;
+  float light_x_, light_y_, light_z_;
+  float diffuse_r_, diffuse_g_, diffuse_b_;
+  float ambient_r_, ambient_g_, ambient_b_;
+
+  // cached calculations
+  float planet_xyz_;
+  float planet_pole_x_equator_x_;
+  float planet_pole_x_equator_y_;
+  float planet_pole_x_equator_z_;
+  float planet_radius2_;
+  float planet_one_over_radius_;
+  float eye_xyz_;
+
+  // misc
+  Texture *tex_;
+  Surface surface_;
+  ArcCosine acos_;
+  int num_regions_;
+  WorkerThreadManager *workers_;
+  volatile bool exiting_;
+  bool rendering_;
+
+public:
+
+  // methods prefixed with 'w' are only called by worker threads!
+  // (unless MULTI_THREADING is false)
+  uint32_t* wGetAddr(int x, int y);
+  void wRenderPixelSpan(int x0, int x1, int y);
+  void wMakeRect(int r, int *x, int *y, int *w, int *h);
+  void wRenderRect(int x0, int y0, int x1, int y1);
+  void wWorkerThreadEntry();
+
+  // these methods are only called by the main thread
+  void CacheCalcs();
+  void SetPlanetXYZR(float x, float y, float z, float r);
+  void SetPlanetPole(float x, float y, float z);
+  void SetPlanetEquator(float x, float y, float z);
+  void SetPlanetSpin(float a);
+  void SetEyeXYZ(float x, float y, float z);
+  void SetLightXYZ(float x, float y, float z);
+  void SetAmbientRGB(float r, float g, float b);
+  void SetDiffuseRGB(float r, float g, float b);
+  void SetSurface(Surface surface);
+  bool CreateWorkerThreads(int num);
+  void UpdateSim();
+  void ParallelRender();
+  void ParallelRenderSync();
+  void SequentialRender();
+  void Render();
+  void Sync();
+  Planet(int numRegions, bool multithreading, Texture *tex);
+  ~Planet();
+};
+
+// Given a region r, derive a rectangle.  Currently this function
+// slices the main output buffer into equal sized rows.
+// This function is used to convert a mutex guarded counter into
+// a rectangular region for a given worker thread to process.
+// This rectangle shouldn't overlap with work being done by other workers.
+// If multithreading, this function is only called by the worker threads.
+void Planet::wMakeRect(int r, int *x, int *y, int *w, int *h) {
+  int dy = surface_.height / num_regions_;
+  *x = 0;
+  *w = surface_.width;
+  *y = r * dy;
+  *h = dy;
+}
+
+
+inline uint32_t* Planet::wGetAddr(int x, int y) {
+  assert(surface_.pixels);
+  return (surface_.pixels + y * surface_.pitch) + x;
+}
+
+
+union Convert {
+  float f;
+  int i;
+  Convert(int x) { i = x; }
+  Convert(float x) { f = x; }
+  const int asInt() { return i; }
+  const float asFloat() { return f; }
+};
+
+
+inline const int AsInteger(const float f) {
+  Convert u(f);
+  return u.asInt();
+}
+
+
+inline const float AsFloat(const int i) {
+  Convert u(i);
+  return u.asFloat();
+}
+
+
+const long int kOneAsInteger = AsInteger(1.0f);
+const float kScaleUp = float(0x00800000);
+const float kScaleDown = 1.0f / kScaleUp;
+
+
+inline float inline_quick_sqrt(float x) {
+  int i;
+  i = (AsInteger(x) >> 1) + (kOneAsInteger >> 1);
+  return AsFloat(i);
+}
+
+
+inline float inline_sqrt(float x) {
+  float y;
+  y = inline_quick_sqrt(x);
+  y = (y * y + x) / (2.0f * y);
+  y = (y * y + x) / (2.0f * y);
+  return y;
+}
+
+
+// This is the meat of the ray tracer.  Given a pixel span (x0, x1) on
+// scanline y, shoot rays into the scene and render what they hit.  Use
+// scanline coherence to do a few optimizations
+void Planet::wRenderPixelSpan(int x0, int x1, int y) {
+  const int kColorBlack = MakeRGBA(0, 0, 0, 0xFF);
+  float y0 = eye_y_;
+  float z0 = eye_z_;
+  float y1 = (static_cast<float>(y) / surface_.height) * 2.0f - 1.0f;
+  float z1 = 0.0f;
+  float dy = (y1 - y0);
+  float dz = (z1 - z0);
+  float dy_dy_dz_dz = dy * dy + dz * dz;
+  float two_dy_y0_y_two_dz_z0_z = 2.0f * dy * (y0 - planet_y_) +
+                                  2.0f * dz * (z0 - planet_z_);
+  float planet_xyz_eye_xyz = planet_xyz_ + eye_xyz_;
+  float y_y0_z_z0 = planet_y_ * y0 + planet_z_ * z0;
+  float oowidth = 1.0f / surface_.width;
+  uint32_t *pixels = this->wGetAddr(x0, y);
+  for (int x = x0; x <= x1; ++x) {
+    // scan normalized screen -1..1
+    float x1 = (static_cast<float>(x) * oowidth) * 2.0f - 1.0f;
+    // eye
+    float x0 = eye_x_;
+    // delta from screen to eye
+    float dx = (x1 - x0);
+    // build a, b, c
+    float a = dx * dx + dy_dy_dz_dz;
+    float b = 2.0f * dx * (x0 - planet_x_) + two_dy_y0_y_two_dz_z0_z;
+    float c = planet_xyz_eye_xyz +
+              -2.0f * (planet_x_ * x0 + y_y0_z_z0) - (planet_radius2_);
+    // calculate discriminant
+    float disc = b * b - 4.0f * a * c;
+
+    // did ray hit the sphere?
+    if (disc < 0.0f) {
+      *pixels = kColorBlack;
+      ++pixels;
+      continue;
+    }
+
+    // calc parametric t value
+    float t = (-b - inline_sqrt(disc)) / (2.0f * a);
+    float px = x0 + t * dx;
+    float py = y0 + t * dy;
+    float pz = z0 + t * dz;
+    float nx = (px - planet_x_) * planet_one_over_radius_;
+    float ny = (py - planet_y_) * planet_one_over_radius_;
+    float nz = (pz - planet_z_) * planet_one_over_radius_;
+
+    float Lx = (light_x_ - px);
+    float Ly = (light_y_ - py);
+    float Lz = (light_z_ - pz);
+    float Lq = 1.0f / inline_quick_sqrt(Lx * Lx + Ly * Ly + Lz * Lz);
+    Lx *= Lq;
+    Ly *= Lq;
+    Lz *= Lq;
+    float d = (Lx * nx + Ly * ny + Lz * nz);
+    float pr = (diffuse_r_ * d) + ambient_r_;
+    float pg = (diffuse_g_ * d) + ambient_g_;
+    float pb = (diffuse_b_ * d) + ambient_b_;
+    float ds = -(nx * planet_pole_x_ +
+                 ny * planet_pole_y_ +
+                 nz * planet_pole_z_);
+    float ang = acos_.TableLerp(ds);
+    float v = ang * kOneOverPI;
+    float dp = planet_equator_x_ * nx +
+               planet_equator_y_ * ny +
+               planet_equator_z_ * nz;
+    float w = dp / sin(ang);
+    if (w > 1.0f) w = 1.0f;
+    if (w < -1.0f) w = -1.0f;
+    float th = acos_.TableLerp(w) * kOneOver2PI;
+    float dps = planet_pole_x_equator_x_ * nx +
+                planet_pole_x_equator_y_ * ny +
+                planet_pole_x_equator_z_ * nz;
+    float u;
+    if (dps < 0.0f)
+      u = th;
+    else
+      u = 1.0f - th;
+
+    int tx = static_cast<int>(u * tex_->width);
+    int ty = static_cast<int>(v * tex_->height);
+    int offset = tx + ty * tex_->width;
+    uint32_t texel = tex_->pixels[offset];
+    float tr = ExtractR(texel);
+    float tg = ExtractG(texel);
+    float tb = ExtractB(texel);
+
+    unsigned int ir = Clamp255(pr * tr);
+    unsigned int ig = Clamp255(pg * tg);
+    unsigned int ib = Clamp255(pb * tb);
+    unsigned int color = MakeRGBA(ir, ig, ib, 0xFF);
+
+    *pixels = color;
+    ++pixels;
+  }
+}
+
+
+// Renders a rectangular area of the screen, scan line at a time
+void Planet::wRenderRect(int x, int y, int w, int h) {
+  for (int j = y; j < (y + h); ++j) {
+    this->wRenderPixelSpan(x, x + w - 1, j);
+  }
+}
+
+
+// Thread entry point Planet::wWorkerThread()
+// This is the main loop for the worker thread(s).  It waits for work
+// by testing a semaphore, which will sleep this thread until work arrives.
+// It then grabs a mutex protected counter (which is also decremented)
+// and uses this value to determine which subregion this thread should be
+// processing.  When rendering is finished the worker then pings the main
+// thread via PostDone() semaphore.
+// If multithreading, this function is only called by the worker threads.
+void Planet::wWorkerThreadEntry() {
+
+  // we're a 'detached' thread...
+  // (so we should automagically die when the main thread exits)
+  while (!exiting_) {
+    // wait for some work
+    workers_->WaitWork();
+
+    // if main thread is exiting, have worker exit too
+    if (exiting_) break;
+    // okay, grab region to work on from worker counter
+    int region = workers_->DecCounter();
+    if (region < 0) {
+      // This indicates we're not sync'ing properly
+      InfoPrintf("Region value went negative!\n");
+      exit(-1);
+    }
+    // convert region # into x0, y0, x1, y1 rectangle
+    int x, y, w, h;
+    this->wMakeRect(region, &x, &y, &w, &h);
+
+    // render this rectangle
+    this->wRenderRect(x, y, w, h);
+
+    // let main thread know we've finished a region
+    workers_->PostDone();
+  }
+}
+
+
+// Entry point for worker thread.  (Can't really pass a member function to
+// pthread_create(), so we have to do this little round-about)
+// If multithreading, this function is only called by the worker threads.
+void* wWorkerThreadEntry(void *args) {
+  // unpack this pointer
+  Planet *pPlanet = reinterpret_cast<Planet*>(args);
+  pPlanet->wWorkerThreadEntry();
+  return NULL;
+}
+
+
+// Create worker threads and pass along our this pointer.
+// If workers_ is NULL, we're running in non-threaded mode.
+bool Planet::CreateWorkerThreads(int num) {
+  if (NULL != workers_) {
+    return workers_->CreateThreadPool(num, ::wWorkerThreadEntry, this);
+  } else {
+    return true;
+  }
+}
+
+
+// Run a simple sim to spin the planet.  Update loop is run once per frame.
+// Called from the main thread only and only when the worker threads are idle.
+void Planet::UpdateSim() {
+  float m = planet_spin_ + 0.01f;
+  // keep in nice range
+  if (m > (kPI * 2.0f))
+    m = m - kPI * 2.0f;
+  SetPlanetSpin(m);
+}
+
+
+// This is the main thread's entry point to dispatch rendering of the planet.
+// First, it sets the region counter to its max value.  This mutex guarded
+// counter is how worker threads determine which region of the diagram they
+// should be working on.  Then it pings the PostWork semaphore multiple times
+// to wake up the sleeping worker threads.
+void Planet::ParallelRender() {
+
+  // At this point, all worker threads are idle and sleeping
+
+  // setup barrier counter before we wake workers
+  workers_->SetCounter(num_regions_);
+  rendering_ = true;
+
+  // wake up the workers
+  for (int i = 0; i < num_regions_; ++i) {
+    workers_->PostWork();
+  }
+  // At this point, all worker threads are awake and busy grabbing
+  // work assignments by reading and decrementing the counter.
+}
+
+
+// ParallelRenderSync will sleep a little by waiting for the workers to
+// finish.  It does that by waiting on the WaitDone semaphore.
+void Planet::ParallelRenderSync() {
+
+  // Only wait if rendering is in progress.
+  if (rendering_) {
+    // wait for all work to be done
+    for (int i = 0; i < num_regions_; ++i) {
+      workers_->WaitDone();
+    }
+    // verify that our counter is where we expect it to be
+    int c = workers_->DecCounter();
+    if (-1 != c) {
+      InfoPrintf("We're not syncing correctly! (%d)\n", c);
+      exit(-1);
+    }
+    rendering_ = false;
+  }
+  // At this point, all worker threads are idle and sleeping again.
+  // The main thread is free to muck with shared data, such
+  // as updating the earth spin in the sim routine.
+}
+
+
+// Performs all rendering from the main thread.
+void Planet::SequentialRender() {
+  this->wRenderRect(0, 0, surface_.width, surface_.height);
+}
+
+
+// Renders the Planet diagram.
+// Picks either parallel or sequential rendering implementation.
+void Planet::Render() {
+  if (NULL == workers_) {
+    this->SequentialRender();
+  } else {
+    this->ParallelRender();
+  }
+}
+
+
+// Waits for a rendering to complete.
+void Planet::Sync() {
+  if (NULL != workers_) {
+    this->ParallelRenderSync();
+  }
+}
+
+
+// pre-calculations to make inner loops faster
+// these need to be recalculated when values change
+void Planet::CacheCalcs() {
+  planet_xyz_ = planet_x_ * planet_x_ +
+                planet_y_ * planet_y_ +
+                planet_z_ * planet_z_;
+  planet_radius2_ = planet_radius_ * planet_radius_;
+  planet_one_over_radius_ = 1.0f / planet_radius_;
+  eye_xyz_ = eye_x_ * eye_x_ + eye_y_ * eye_y_ + eye_z_ * eye_z_;
+  // spin vector from center->equator
+  planet_equator_x_ = cos(planet_spin_);
+  planet_equator_y_ = 0.0f;
+  planet_equator_z_ = sin(planet_spin_);
+  // cache cross product of pole & equator
+  planet_pole_x_equator_x_ = planet_pole_y_ * planet_equator_z_ -
+                             planet_pole_z_ * planet_equator_y_;
+  planet_pole_x_equator_y_ = planet_pole_z_ * planet_equator_x_ -
+                             planet_pole_x_ * planet_equator_z_;
+  planet_pole_x_equator_z_ = planet_pole_x_ * planet_equator_y_ -
+                             planet_pole_y_ * planet_equator_x_;
+}
+
+
+void Planet::SetPlanetXYZR(float x, float y, float z, float r) {
+  planet_x_ = x;
+  planet_y_ = y;
+  planet_z_ = z;
+  planet_radius_ = r;
+  CacheCalcs();
+}
+
+
+void Planet::SetEyeXYZ(float x, float y, float z) {
+  eye_x_ = x;
+  eye_y_ = y;
+  eye_z_ = z;
+  CacheCalcs();
+}
+
+
+void Planet::SetLightXYZ(float x, float y, float z) {
+  light_x_ = x;
+  light_y_ = y;
+  light_z_ = z;
+  CacheCalcs();
+}
+
+
+void Planet::SetAmbientRGB(float r, float g, float b) {
+  ambient_r_ = r;
+  ambient_g_ = g;
+  ambient_b_ = b;
+  CacheCalcs();
+}
+
+
+void Planet::SetDiffuseRGB(float r, float g, float b) {
+  diffuse_r_ = r;
+  diffuse_g_ = g;
+  diffuse_b_ = b;
+  CacheCalcs();
+}
+
+
+void Planet::SetPlanetPole(float x, float y, float z) {
+  planet_pole_x_ = x;
+  planet_pole_y_ = y;
+  planet_pole_z_ = z;
+  CacheCalcs();
+}
+
+
+void Planet::SetPlanetEquator(float x, float y, float z) {
+  // this is really over-ridden by spin at the momenent
+  planet_equator_x_ = x;
+  planet_equator_y_ = y;
+  planet_equator_z_ = z;
+  CacheCalcs();
+}
+
+
+void Planet::SetPlanetSpin(float a) {
+  planet_spin_ = a;
+  CacheCalcs();
+}
+
+
+void Planet::SetSurface(Surface surface) {
+  surface_ = surface;
+}
+
+
+// Setups and initializes planet data structures.
+// Seed planet, eye, and light
+Planet::Planet(int numRegions, bool multi, Texture *tex) :
+    planet_radius_(1.0f),
+    planet_spin_(0.0f),
+    planet_x_(0.0f),
+    planet_y_(0.0f),
+    planet_z_(0.0f),
+    planet_pole_x_(0.0f),
+    planet_pole_y_(0.0f),
+    planet_pole_z_(0.0f),
+    planet_equator_x_(0.0f),
+    planet_equator_y_(0.0f),
+    planet_equator_z_(0.0f),
+    eye_x_(0.0f),
+    eye_y_(0.0f),
+    eye_z_(0.0f),
+    light_x_(0.0f),
+    light_y_(0.0f),
+    light_z_(0.0f),
+    diffuse_r_(0.0f),
+    diffuse_g_(0.0f),
+    diffuse_b_(0.0f),
+    ambient_r_(0.0f),
+    ambient_g_(0.0f),
+    ambient_b_(0.0f),
+    planet_xyz_(0.0f),
+    planet_pole_x_equator_x_(0.0f),
+    planet_pole_x_equator_y_(0.0f),
+    planet_pole_x_equator_z_(0.0f),
+    planet_radius2_(0.0f),
+    planet_one_over_radius_(0.0f),
+    eye_xyz_(0.0f),
+    surface_(NULL, 0, 0) {
+  num_regions_ = numRegions;
+  workers_ = multi ? new WorkerThreadManager() : NULL;
+  tex_ = tex;
+  exiting_ = false;
+  rendering_ = false;
+
+  this->SetPlanetXYZR(0.0f, 0.0f, 48.0f, 4.0f);
+  this->SetEyeXYZ(0.0f, 0.0f, -14.0f);
+  this->SetLightXYZ(-8.0f, -4.0f, 2.0f);
+  this->SetAmbientRGB(0.4f, 0.4f, 0.4f);
+  this->SetDiffuseRGB(0.8f, 0.8f, 0.8f);
+  this->SetPlanetPole(0.0f, 1.0f, 0.0f);
+  this->SetPlanetEquator(1.0f, 0.0f, 0.0f);
+  this->SetPlanetSpin(kPI / 2.0f);
+}
+
+
+// Frees up planet resources.
+Planet::~Planet() {
+  if (workers_) {
+    exiting_ = true;
+    // wake up the worker threads from their slumber
+    workers_->PostWorkAll();
+    workers_->JoinAll();
+    delete workers_;
+  }
+}
+
+
+// Clamps input to the max we can realistically support.
+static int ClampThreads(int num) {
+  const int max = 128;
+  if (num > max) {
+    return max;
+  }
+  return num;
+}
+
+
+static void PrintCredits() {
+  static const char *credit =
+    "\n"
+    "Image Credit:\n"
+    "\n"
+    "NASA Goddard Space Flight Center Image by Reto Stöckli (land surface,\n"
+    "shallow water, clouds). Enhancements by Robert Simmon (ocean color,\n"
+    "compositing, 3D globes, animation).\n"
+    "Data and technical support: MODIS Land Group; MODIS Science Data,\n"
+    "Support Team; MODIS Atmosphere Group; MODIS Ocean Group\n"
+    "Additional data:\n"
+    "USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing\n"
+    "Flagstaff Field Center (Antarctica); Defense Meteorological\n"
+    "Satellite Program (city lights).\n"
+    "\n";
+  InfoPrintf(credit);
+}
+
+// If user specifies options on cmd line, parse them
+// here and update global settings as needed.
+static void ParseCmdLineArgs(int argc, const char *argn[], const char *argv[]) {
+  // look for cmd line args
+  PrintCredits();
+  if (argc > 1) {
+    for (int i = 1; i < argc; ++i) {
+      if (argn[i] == strstr(argn[i], "numthreads")) {
+        int numthreads = atoi(argv[i]);
+        if (numthreads > 1) {
+          g_multi_threading = true;
+          g_num_threads = numthreads;
+          g_num_regions = numthreads * kRegionRatio;
+          InfoPrintf("Using %d threads\n", numthreads);
+        } else {
+          InfoPrintf("Could not parse numthreads=%s.\n", argv[i]);
+        }
+      } else if (argn[i] == strstr(argn[i], "usesysconf")) {
+        if (argv[i] == strstr(argv[i], "true")) {
+          g_multi_threading = true;
+          g_ask_sysconf = true;
+        } else if (argv[i] == strstr(argv[i], "false")) {
+          g_multi_threading = false;
+        } else {
+          InfoPrintf("Could not parse usesysconf=%s.\n", argv[i]);
+        }
+      } else if (argn[i] == strstr(argn[i], "xwidth")) {
+        int w = atoi(argv[i]);
+        if ((w > 0) && (w < kMaxWindow)) g_window_width = w;
+      } else if (argn[i] == strstr(argn[i], "xheight")) {
+        int h = atoi(argv[i]);
+        if ((h > 0) && (h < kMaxWindow)) g_window_height = h;
+      } else if (argn[i] == strstr(argn[i], "frames")) {
+        int f = atoi(argv[i]);
+        if ((f > 0) && (f < kMaxFrames)) g_num_frames = f;
+      } else if (argn[i] == strstr(argn[i], "id")) {
+        /* ignore id */
+      } else if (argn[i] == strstr(argn[i], "src")) {
+        /* ignore src */
+      } else if (argn[i] == strstr(argn[i], "style")) {
+        /* ignore style */
+      } else if (argn[i] == strstr(argn[i], "type")) {
+        /* ignore type */
+      } else {
+        if (argn[i] != strstr(argn[i], "help")) {
+          InfoPrintf("unknown option %s=%s\n", argn[i], argv[i]);
+        }
+        InfoPrintf("Earth Pepper Demo\n"
+                   "usage: numthreads=\"n\"   render using n threads.\n"
+                   "       usesysconf=true  use sysconf to set thread count."
+                   "\n"
+                   "       xwidth=\"w\"       width of window.\n"
+                   "       xheight=\"h\"      height of window.\n"
+                   "       framecount=\"n\"   number of frames.\n"
+                   "       help             show this screen.\n");
+      }
+    }
+  }
+
+  InfoPrintf("Multi-threading %s.\n",
+             g_multi_threading ? "enabled" : "disabled");
+
+  // see if the system can tell us # cpus
+  if ((g_ask_sysconf) && (g_multi_threading)) {
+    int ncpu = sysconf(_SC_NPROCESSORS_ONLN);
+    if (ncpu > 1) {
+      InfoPrintf("Using %d processors based on sysconf.\n", ncpu);
+      g_num_threads = ncpu;
+      g_num_regions = ncpu * kRegionRatio;
+    }
+  }
+
+  // clamp threads and regions
+  g_num_threads = ClampThreads(g_num_threads);
+  g_num_regions = ClampThreads(g_num_regions);
+}
+
+Planet *g_planet = NULL;
+
+// Parses cmd line options, initializes surface, runs the demo & shuts down.
+extern "C" void Earth_Init(int argc, const char *argn[], const char *argv[]) {
+  ParseCmdLineArgs(argc, argn, argv);
+  g_planet = new Planet(g_num_regions, g_multi_threading, &g_earth);
+  if (!g_planet->CreateWorkerThreads(g_num_threads)) {
+    DebugPrintf("Earth_Init: thread creation failed.  g_num_threads: %d\n",
+        g_num_threads);
+    exit(-1);
+  }
+}
+
+extern "C" void Earth_Draw(uint32_t *image_data, int width, int height) {
+  g_planet->SetSurface(Surface(image_data, width, height));
+  g_planet->UpdateSim();
+  g_planet->Render();
+}
+
+extern "C" void Earth_Sync() {
+  g_planet->Sync();
+  g_planet->SetSurface(Surface(NULL, 0, 0));
+}