(mkosarek) Fix for wrong timestep

17 files changed, 222 insertions, 57 deletions

diff --git a/2d/_collisions/polygon_polygon/dist/output.wasm b/2d/_collisions/polygon_polygon/dist/output.wasm
index a047d19..055fbb7 100755
--- a/2d/_collisions/polygon_polygon/dist/output.wasm
+++ b/2d/_collisions/polygon_polygon/dist/output.wasm
diff --git a/2d/_collisions/polygon_polygon/main.cpp b/2d/_collisions/polygon_polygon/main.cpp
index 620edaa..9cb3eb2 100644
--- a/2d/_collisions/polygon_polygon/main.cpp
+++ b/2d/_collisions/polygon_polygon/main.cpp
@@ -72,7 +72,7 @@ struct Rigidbody {
             
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
+            force += forceToApply;
             
 
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
diff --git a/2d/rigidbody/rigidbody_1.html b/2d/rigidbody/rigidbody_1.html
index b98d292..0d50904 100644
--- a/2d/rigidbody/rigidbody_1.html
+++ b/2d/rigidbody/rigidbody_1.html
@@ -200,7 +200,7 @@
             <span class="code_comment">// to calculate the fractional amount of force that was applied in this frame.</span>
             <span class="code_keyword">float32</span> impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             <span class="code_keyword">Vector2</span> forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
+            force += forceToApply;
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
         }
 
diff --git a/2d/rigidbody/rigidbody_1/dist/output.wasm b/2d/rigidbody/rigidbody_1/dist/output.wasm
index f6625a9..b9f4c37 100755
--- a/2d/rigidbody/rigidbody_1/dist/output.wasm
+++ b/2d/rigidbody/rigidbody_1/dist/output.wasm
diff --git a/2d/rigidbody/rigidbody_1/main.cpp b/2d/rigidbody/rigidbody_1/main.cpp
index 88c322c..a327fee 100644
--- a/2d/rigidbody/rigidbody_1/main.cpp
+++ b/2d/rigidbody/rigidbody_1/main.cpp
@@ -61,8 +61,7 @@ struct Rigidbody {
             
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
-            
+            force += forceToApply;
 
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
         }
@@ -301,8 +300,8 @@ EM_BOOL onMouseMove(int eventType, const EmscriptenMouseEvent *mouseEvent, void
 		return true;
 	}
 
-	pointer.force.x = static_cast<float32>(mouseEvent->movementX) * 100000.f;
-	pointer.force.y = static_cast<float32>(-mouseEvent->movementY) * 100000.f;
+	pointer.force.x = static_cast<float32>(mouseEvent->movementX) * 1000.f;
+	pointer.force.y = static_cast<float32>(-mouseEvent->movementY) * 1000.f;
 
 	pointer.body.position.x = static_cast<float32>(mouseEvent->targetX);
 	pointer.body.position.y = static_cast<float32>(600.f - mouseEvent->targetY);
diff --git a/2d/rigidbody/rigidbody_1/snippet3.cpp b/2d/rigidbody/rigidbody_1/snippet3.cpp
index 4727a9a..d3ecc4f 100644
--- a/2d/rigidbody/rigidbody_1/snippet3.cpp
+++ b/2d/rigidbody/rigidbody_1/snippet3.cpp
@@ -31,7 +31,7 @@ struct Rigidbody {
             // to calculate the fractional amount of force that was applied in this frame.
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
+            force += forceToApply;
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
         }
 
diff --git a/2d/rigidbody/rigidbody_2/dist/output.wasm b/2d/rigidbody/rigidbody_2/dist/output.wasm
index 29c319a..fb79e45 100755
--- a/2d/rigidbody/rigidbody_2/dist/output.wasm
+++ b/2d/rigidbody/rigidbody_2/dist/output.wasm
diff --git a/2d/rigidbody/rigidbody_2/main.cpp b/2d/rigidbody/rigidbody_2/main.cpp
index 123cf7e..44a3c53 100644
--- a/2d/rigidbody/rigidbody_2/main.cpp
+++ b/2d/rigidbody/rigidbody_2/main.cpp
@@ -69,7 +69,7 @@ struct Rigidbody {
             
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
+            force += forceToApply;
 
             // New! Increment the torque for each force
             torque += i.pointOfApplication.getPerp().dot(forceToApply);
diff --git a/2d/rigidbody/rigidbody_3/dist/output.wasm b/2d/rigidbody/rigidbody_3/dist/output.wasm
index b89435a..0a8a974 100755
--- a/2d/rigidbody/rigidbody_3/dist/output.wasm
+++ b/2d/rigidbody/rigidbody_3/dist/output.wasm
diff --git a/2d/rigidbody/rigidbody_3/main.cpp b/2d/rigidbody/rigidbody_3/main.cpp
index e34f444..2a0af24 100644
--- a/2d/rigidbody/rigidbody_3/main.cpp
+++ b/2d/rigidbody/rigidbody_3/main.cpp
@@ -72,7 +72,7 @@ struct Rigidbody {
             
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
             Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
-            force += forceToApply * impulseDtSeconds;
+            force += forceToApply;
             torque += i.pointOfApplication.getPerp().dot(forceToApply);
 
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
diff --git a/3d/rigidbody.html b/3d/rigidbody.html
index db91bd0..68244de 100644
--- a/3d/rigidbody.html
+++ b/3d/rigidbody.html
@@ -69,26 +69,37 @@
 <article>
   <h1>Rigidbody in 3D</h1>
   <section>
-  <section>
-	<h2>
-	  Live Example
-	</h2>
-    <div class="opengl_canvas_container">
-      <canvas id="gl_canvas" width="800" height="600"></canvas>
-      <button id="gl_canvas_play" class="play_button">
-        Play
-      </button>
-      <button id="gl_canvas_stop" class="stop_button">
-        Stop
-      </button>
-    </div>
-	
-    <footer id="references">
-      <h2>References</h2>
-      <ul>
-      </ul>
-    </footer>
-  </section>
+    <section>
+      <h2>Quaternion Time</h2>
+      <p>
+        I hate to start off the article like this. I really do. But it really wouldn't be a discussion of 3D simulation if we didn't jump right into quaternions. Before I start, however, I recommend you take a look at <a href='https://www.3dgep.com/understanding-quaternions'>this article</a>. Quaternions have been written about over and over throughout the years (and I have read many articles about them over and over throughout the years), so I will not waste your time describing every single detail here. The article that I linked to should provide you enough information to begin to understand what quaternions are and why they're important. That being said, I will provide a brief intro to quaternions here, as well as my own C++ implementation of their algebra. (This article is also quite useful: <a href='http://danceswithcode.net/engineeringnotes/quaternions/quaternions.html'>Dance's With Code Website</a>)
+        <br/><br/>
+        
+      </p>
+    </section>
+    <section>
+	  <h2>
+	    Live Example
+	  </h2>
+      <p>
+        <button id='force_apply'>Click Me</button>
+      </p>
+      <div class="opengl_canvas_container">
+        <canvas id="gl_canvas" width="800" height="600"></canvas>
+        <button id="gl_canvas_play" class="play_button">
+          Play
+        </button>
+        <button id="gl_canvas_stop" class="stop_button">
+          Stop
+        </button>
+      </div>
+	  
+      <footer id="references">
+        <h2>References</h2>
+        <ul>
+        </ul>
+      </footer>
+    </section>
 </article>
 		</main>
 	</body>
diff --git a/3d/rigidbody.html.content b/3d/rigidbody.html.content
index 8bbf294..5a3eca2 100644
--- a/3d/rigidbody.html.content
+++ b/3d/rigidbody.html.content
@@ -17,24 +17,35 @@
 <article>
   <h1>Rigidbody in 3D</h1>
   <section>
-  <section>
-	<h2>
-	  Live Example
-	</h2>
-    <div class="opengl_canvas_container">
-      <canvas id="gl_canvas" width="800" height="600"></canvas>
-      <button id="gl_canvas_play" class="play_button">
-        Play
-      </button>
-      <button id="gl_canvas_stop" class="stop_button">
-        Stop
-      </button>
-    </div>
-	
-    <footer id="references">
-      <h2>References</h2>
-      <ul>
-      </ul>
-    </footer>
-  </section>
+    <section>
+      <h2>Quaternion Time</h2>
+      <p>
+        I hate to start off the article like this. I really do. But it really wouldn't be a discussion of 3D simulation if we didn't jump right into quaternions. Before I start, however, I recommend you take a look at <a href='https://www.3dgep.com/understanding-quaternions'>this article</a>. Quaternions have been written about over and over throughout the years (and I have read many articles about them over and over throughout the years), so I will not waste your time describing every single detail here. The article that I linked to should provide you enough information to begin to understand what quaternions are and why they're important. That being said, I will provide a brief intro to quaternions here, as well as my own C++ implementation of their algebra. (This article is also quite useful: <a href='http://danceswithcode.net/engineeringnotes/quaternions/quaternions.html'>Dance's With Code Website</a>)
+        <br/><br/>
+        
+      </p>
+    </section>
+    <section>
+	  <h2>
+	    Live Example
+	  </h2>
+      <p>
+        <button id='force_apply'>Click Me</button>
+      </p>
+      <div class="opengl_canvas_container">
+        <canvas id="gl_canvas" width="800" height="600"></canvas>
+        <button id="gl_canvas_play" class="play_button">
+          Play
+        </button>
+        <button id="gl_canvas_stop" class="stop_button">
+          Stop
+        </button>
+      </div>
+	  
+      <footer id="references">
+        <h2>References</h2>
+        <ul>
+        </ul>
+      </footer>
+    </section>
 </article>
diff --git a/3d/rigidbody/dist/output.wasm b/3d/rigidbody/dist/output.wasm
index 98d25e5..8ebe0dd 100755
--- a/3d/rigidbody/dist/output.wasm
+++ b/3d/rigidbody/dist/output.wasm
diff --git a/3d/rigidbody/main.cpp b/3d/rigidbody/main.cpp
index c83018b..90c6bc8 100644
--- a/3d/rigidbody/main.cpp
+++ b/3d/rigidbody/main.cpp
@@ -13,17 +13,96 @@
 #include <cmath>
 #include <cfloat>
 
+struct Impulse {
+    Vector3 force = { 0, 0, 0 };
+    Vector3 pointOfApplication = { 0, 0, 0 };
+    float32 timeOfApplicationSeconds = 0.016f;
+    float32 timeAppliedSeconds = 0.f;
+    bool isDead = false;
+};
+
+const int32 MAX_IMPULSES = 4;
+
 struct Rigidbody3d {
+    int32 numImpulses = 0;
+    Impulse activeImpulses[MAX_IMPULSES];
     Vector3 velocity;
     Vector3 position;
+    float32 mass = 1.f;
+
+    Vector3 rotationalVelocity;
+    Quaternion rotation;
+    float32 momentOfInertia = 1.f;
+
+    void reset() {
+        numImpulses = 0;
+        velocity = { 0, 0, 0};
+        rotationalVelocity = { 0, 0, 0 };
+    }
+
+    void applyImpulse(Impulse i) {
+        if (numImpulses > MAX_IMPULSES) {
+            printf("Unable to apply impulse. Buffer full.\n");
+            return;
+        }
+
+        activeImpulses[numImpulses] = i;
+        numImpulses++;
+    }
+
+    void update(float32 deltaTimeSeconds) {
+        // Apply gravity
+        //velocity += (Vector3 { 0.f, -9.8f, 0.f } * deltaTimeSeconds);
+
+        Vector3 force = { 0.f, 0.f, 0.f };
+        Vector3 torque = { 0.f, 0.f, 0.f };
+        for (int32 idx = 0; idx < numImpulses; idx++) {
+            Impulse& i = activeImpulses[idx];
 
-    void update(float32 dtSeconds) {
+            float32 nextTimeAppliedSeconds = i.timeAppliedSeconds + deltaTimeSeconds;
+            if (nextTimeAppliedSeconds >= i.timeOfApplicationSeconds) {
+                nextTimeAppliedSeconds = i.timeOfApplicationSeconds;
+                i.isDead = true;
+            }
+            
+            float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
+            Vector3 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
+            force += forceToApply;
+
+            force.printDebug("Force applied\n");
+
+            torque += i.pointOfApplication.cross(force).dot(forceToApply);
+            i.timeAppliedSeconds = nextTimeAppliedSeconds;
+        }
         
+        Vector3 acceleration = force / mass;
+        velocity += (acceleration * deltaTimeSeconds);
+        position += (velocity * deltaTimeSeconds);
+
+	    Vector3 rotationalAcceleration = torque / momentOfInertia;
+		rotationalVelocity += (rotationalAcceleration * deltaTimeSeconds);
+
+        Quaternion rotationVelocityQuat = { 0, rotationalVelocity.x, rotationalVelocity.y, rotationalVelocity.z };
+        Quaternion dqDt = (rotationVelocityQuat  * rotation) * 0.5f;
+		rotation = rotation + (dqDt * deltaTimeSeconds);
+
+        for (int32 idx = 0; idx < numImpulses; idx++) {
+            if (activeImpulses[idx].isDead) {
+                for (int j = idx + 1; j < numImpulses; j++) {
+                    activeImpulses[j - 1] = activeImpulses[j];
+                }
+
+                idx = idx - 1;
+                numImpulses--;
+            }
+        }
     }
 };
 
 struct Cube {
 	Mesh3d mesh;
+    Rigidbody3d body;
+    float32 scale = 10.f;
 
 	void load(Renderer3d* renderer) {
 	    Vertex3d cubeVertices[] = {
@@ -87,12 +166,18 @@ struct Cube {
 
 
 		mesh.load(&cubeVertices[0], 8, cubeIndices, 36, renderer);
+
+        body.position = Vector3 { 0.f, 0.f, 0.f };
+        body.velocity = Vector3 { 0.f, 0.f, 0.f };
+        mesh.model = Mat4x4().scale(scale);
+
+        float32 singleFaceArea = scale * scale;
+        body.momentOfInertia = (body.mass * singleFaceArea) / 6.f;
 	}
 
 	void update(float32 dtSeconds) {
-        float32 multiplier = (PI / 8.f) * dtSeconds;
-        Vector3 currentRotation = Vector3 { multiplier, multiplier, multiplier };
-		mesh.model = mesh.model.rotate(currentRotation.x, currentRotation.y, currentRotation.z);
+        body.update(dtSeconds);
+		mesh.model = mesh.model.translate(body.position) * body.rotation.toMatrix();
 	}
 
 	void render(Renderer3d* renderer) {
@@ -106,6 +191,7 @@ struct Cube {
 
 EM_BOOL onPlayClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData);
 EM_BOOL onStopClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData);
+EM_BOOL onForceApplicationRequested(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData);
 
 void load();
 void update(float32 time, void* userData);
@@ -122,14 +208,17 @@ int main() {
 	context.init("#gl_canvas");
     emscripten_set_click_callback("#gl_canvas_play", NULL, false, onPlayClicked);
     emscripten_set_click_callback("#gl_canvas_stop", NULL, false, onStopClicked);
+    emscripten_set_click_callback("#force_apply", NULL, false, onForceApplicationRequested);
     return 0;
 }
 
 void load() {
     renderer.load(&context);
+    cube.scale = 12.f;
+    cube.body.mass = 100.f;
 	cube.load(&renderer);
-	camera.projection  = Mat4x4().getPerspectiveProjection(0.1f, 100.f, PI / 2.f, 800.f / 600.f);
-	camera.view = Mat4x4().translate({ 0, 0, -10 });
+	camera.projection  = Mat4x4().getPerspectiveProjection(0.1f, 10000.f, DEG_TO_RAD(60.f), 800.f / 600.f);
+	camera.view = Mat4x4().translate({ 0, 0, -250 });
     mainLoop.run(update);
 }
 
@@ -162,3 +251,12 @@ EM_BOOL onStopClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, voi
     unload();
     return true;
 }
+
+EM_BOOL onForceApplicationRequested(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData) {
+    printf("Force applied\n");
+    Impulse base;
+    base.force = { 0, 1000, 0 };
+    base.pointOfApplication = { 0, 1, 0 };
+    cube.body.applyImpulse(base);
+    return true;
+} 
diff --git a/resources.html.content b/resources.html.content
new file mode 100644
index 0000000..2b3aef1
--- /dev/null
+++ b/resources.html.content
@@ -0,0 +1,12 @@
+<article>
+  <h1>Resources</h1>
+  <section>
+    <p>Here are a set of books and resources that I have found particularly helpful in forming my understanding of physics engines. I highly recommend going through all of these resource.</p>
+  </section>
+  <section>
+    <h2>Mathematics</h2>
+    <ul>
+      <li><a href='http://canvas.projekti.info/ebooks/Mathematics%20for%203D%20Game%20Programming%20and%20Computer%20Graphics,%20Third%20Edition.pdf'>Mathematics for 3D Game Programming and Computer Graphics, Third Edition</a>: a great resource on foundational mathematics for computer graphics. I am linking to the free pdf version here so that you can test drive it, but I highly recommend having a physical copy of this book on your shelf. It is a simple and elegant reference for all things computer graphics.</li>
+    </ul>
+  </section>
+</article>
diff --git a/shared_cpp/mathlib.cpp b/shared_cpp/mathlib.cpp
index b7748fe..fb09cd9 100644
--- a/shared_cpp/mathlib.cpp
+++ b/shared_cpp/mathlib.cpp
@@ -155,6 +155,13 @@ Vector3 Vector3::operator+(const Vector3& v2) {
 	return add(v2);
 }
 
+Vector3& Vector3::operator+=(Vector3 other) {
+    x += other.x;
+    y += other.y;
+    z += other.z;
+    return *this;
+}
+
 Vector3 Vector3::operator-(const Vector3& v2) {
 	return subtract(v2);
 }
@@ -167,6 +174,14 @@ Vector3 Vector3::operator*(float value) {
 	return scale(value);
 }
 
+Vector3 Vector3::operator/(const Vector3& v2) {
+    return {
+        x / v2.x,
+        y / v2.y,
+        z / v2.z        
+    };
+}
+
 Vector3 Vector3::operator*(const Vector3& v2) {
 	return {
 	    x * v2.x,
@@ -623,3 +638,16 @@ Mat4x4 Quaternion::toMatrix() const {
 float Quaternion::dot(const Quaternion& other) const {
 	return w * other.w + x * other.x + y * other.y + z * other.z;
 }
+
+Quaternion quaternionFromRotation(Vector3 axis, float angleRadians) {
+    float halfAngleRadians = angleRadians / 2.f;
+    float cosHalfAngRad = cosf(halfAngleRadians);
+    float sinHalfAngRad = sinf(halfAngleRadians);
+
+    return {
+        cosHalfAngRad,
+        axis.x * sinHalfAngRad,
+        axis.y * sinHalfAngRad,
+        axis.z * sinHalfAngRad
+    };
+}
diff --git a/shared_cpp/mathlib.h b/shared_cpp/mathlib.h
index d550e90..e3c6875 100644
--- a/shared_cpp/mathlib.h
+++ b/shared_cpp/mathlib.h
@@ -18,6 +18,8 @@
 #define ABS(x) (x < 0 ? -x : x)
 #define SIGN(x) (x < 0 ? -1 : 1)
 #define PI 3.141592653589793238463
+#define DEG_TO_RAD(x) (x * (PI / 180.f))
+#define RAD_TO_DEG(x) (x * (180.f / PI))
 
 struct Vector2 {
     float x = 0;
@@ -58,10 +60,12 @@ struct Vector3 {
     Vector3 normalize();
 
     Vector3 operator+(const Vector3& v2);
+    Vector3& operator+=(Vector3 other);
     Vector3 operator-(const Vector3& v2);
     Vector3 operator-();
     Vector3 operator*(float value);
     Vector3 operator*(const Vector3& v2);
+    Vector3 operator/(const Vector3& v2);
     float operator[](int index);
     
     void printDebug(const char* name);
@@ -75,7 +79,7 @@ struct Vector4 {
 
     Vector4();
     Vector4(float value);
-    Vector4(float inX = 0.f, float inY = 0.f, float inZ = 0.f, float inW = 1.f);
+    Vector4(float inX, float inY, float inZ, float inW);
     Vector4 fromColor(float r, float g, float b, float a);
 	Vector4 toNormalizedColor();
 
@@ -126,10 +130,10 @@ struct Mat4x4 {
 };
 
 struct Quaternion {
+    float w = 0;
     float x = 0;
     float y = 0;
     float z = 0;
-    float w = 0;
 
     float operator [](int index);
 	Quaternion operator*(const Quaternion& other) const;
@@ -142,3 +146,5 @@ struct Quaternion {
 	float length() const;
 	float dot(const Quaternion& other) const;
 };
+
+Quaternion quaternionFromRotation(Vector3 axis, float angleRadians);