Some minor updates to SAT explanation, and made icons work everywhere

3 files changed, 65 insertions, 14 deletions

diff --git a/2d/_collisions/polygon_polygon/dist/output.wasm b/2d/_collisions/polygon_polygon/dist/output.wasm
index a30f0c4..8e0443b 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 c458299..348e8d2 100644
--- a/2d/_collisions/polygon_polygon/main.cpp
+++ b/2d/_collisions/polygon_polygon/main.cpp
@@ -34,6 +34,7 @@ struct Rigidbody {
     void reset() {
         numImpulses = 0;
         velocity = { 0, 0 };
+        rotationalVelocity = 0.f;
     }
 
     void setMomentOfInertia(float32 moi) {
@@ -158,7 +159,7 @@ struct ConvexPolygon {
         edges = new Edge[numVertices]; // This will be filled in later when we are doing our SAT calculation.
 
         // Calculate moment of inertia
-        body.setMomentOfInertia((PI * body.mass) / 2.f);
+        body.momentOfInertia = (PI * (width * height * body.mass)) / 4.f;
 	}
 
 	void update(float32 dtSeconds) {
@@ -223,31 +224,29 @@ void load() {
     renderer.load(&context);
 
 	for (int index = 0; index < 4; index++) {
-		polygons[index].width = 50.f;
-		polygons[index].height = 50.f;
+        polygons[index].body.reset();
 
 		if (index == 0) {
 			polygons[index].body.position = { context.width / 4.f, context.height / 4.f };
             polygons[index].body.velocity = { 100.f, 200.f };
             polygons[index].body.mass = 2.f;
-            polygons[index].body.rotationalVelocity = 0.2f;
 		} else if (index == 1) {
 			polygons[index].body.position = { context.width / 4.f, context.height * (3.f /4.f) };
             polygons[index].body.velocity = { 50.f, -50.f };
             polygons[index].body.mass = 4.f;
-            polygons[index].body.rotationalVelocity = -0.5f;
 		} else if (index == 2) {
 			polygons[index].body.position = { context.width * (3.f / 4.f), context.height * (3.f / 4.f) };
             polygons[index].body.velocity = { -100.f, -50.f };
             polygons[index].body.mass = 6.f;
-            polygons[index].body.rotationalVelocity = 0.9f;
 		} else if (index == 3) {
 			polygons[index].body.position = { context.width * (3.f / 4.f), context.height / 4.f };
             polygons[index].body.velocity = { -150.f, 50.f };
             polygons[index].body.mass = 8.f;
-            polygons[index].body.rotationalVelocity = 1.4f;
 		}
 
+        polygons[index].width = (polygons[index].body.mass / 2.f) * 20.f;
+		polygons[index].height = (polygons[index].body.mass / 2.f) * 20.f;
+
 		polygons[index].numVertices = (index + 1) * 3;
 		polygons[index].color = Vector4 {
 			index == 0 || index == 3 ? 255.f : 0.f,
@@ -284,9 +283,9 @@ bool projectionsOverlap(Vector2 first, Vector2 second) {
 }
 
 float32 getProjectionOverlap(Vector2 first, Vector2 second) {
-	float32 firstOverlap = fabs(first.x - second.y);
-	float32 secondOverlap = fabs(second.x - first.y);
-	return firstOverlap > secondOverlap ? secondOverlap : firstOverlap;
+	float32 e = MIN(first.y, second.y);
+    float32 f = MAX(first.x, second.x);
+	return e - f;
 }
 
 const float32 EPSILON = 1.f;
@@ -374,13 +373,12 @@ void resolveCollision(Rigidbody* first, Rigidbody* second, IntersectionResult* i
     float32 linearDenomPart = collisionNormal.dot(collisionNormal * (1.f / first->mass + 1.f / second->mass));
 	float32 rotationalDenomPart = (firstPerpNorm * firstPerpNorm) / first->momentOfInertia + (sndPerpNorm * sndPerpNorm) / second->momentOfInertia;
 
-    // @TODO: Most of my 2D rotational work is pretty broken. Let's ignore it for the time being;
-    float32 impulseMagnitude = numerator / (linearDenomPart);// + rotationalDenomPart);
+    float32 impulseMagnitude = numerator / (linearDenomPart + rotationalDenomPart);
     first->velocity = first->velocity + (collisionNormal * (impulseMagnitude / first->mass));
 	second->velocity = second->velocity - (collisionNormal * (impulseMagnitude / second->mass));
 
-    // first->rotationalVelocity = first->rotationalVelocity + firstPerp.dot(collisionNormal * impulseMagnitude) / first->momentOfInertia;
-    // second->rotationalVelocity = second->rotationalVelocity - secondPerp.dot(collisionNormal * impulseMagnitude) / second->momentOfInertia;
+    first->rotationalVelocity = first->rotationalVelocity + firstPerp.dot(collisionNormal * impulseMagnitude) / first->momentOfInertia;
+    second->rotationalVelocity = second->rotationalVelocity - secondPerp.dot(collisionNormal * impulseMagnitude) / second->momentOfInertia;
 }
 
 void update(float32 deltaTimeSeconds, void* userData) {
@@ -430,6 +428,7 @@ void update(float32 deltaTimeSeconds, void* userData) {
 
 			first->update(frameTimeRemaining);
 			second->update(frameTimeRemaining);
+            i = 0;
 		}
     }
 
diff --git a/2d/_collisions/polygon_polygon/snippet1.cpp b/2d/_collisions/polygon_polygon/snippet1.cpp
new file mode 100644
index 0000000..3277cf9
--- /dev/null
+++ b/2d/_collisions/polygon_polygon/snippet1.cpp
@@ -0,0 +1,52 @@
+
+Vector2 getProjection(Vector2* vertices, int numVertices, Vector2 axis) {
+    // Find the min and max vertex projections
+    float32 min = axis.dot(vertices[0]);
+    float32 max = min;
+
+    for (int v = 1; v < numVertices; v++) {
+        float32 d = axis.dot(vertices[v]);
+
+        if (d < min) {
+            min = d;
+        } else if (d > max) {
+            max = d;
+        }
+    }
+
+    return Vector2 { min, max };
+}
+
+bool projectionsOverlap(Vector2 first, Vector2 second) {
+    return first.x <= second.y && second.x <= first.y;
+}
+
+bool doIntersect(ConvexPolygon* first, ConvexPolygon* second) {
+    IntersectionResult ir;
+
+    // Check agaisnt the edges of the first polygon
+    for (int i = 0; i < first->numVertices; i++) {
+        Vector2 normal = first->edges[i].normal;
+
+        Vector2 firstProj = getProjection(first->transformedVertices, first->numVertices, normal);
+        Vector2 secondProj = getProjection(second->transformedVertices, second->numVertices, normal);
+
+        if (!projectionsOverlap(firstProj, secondProj)) {
+            return false;
+        }
+    }
+
+    // Check against the edges of the second polygon
+    for (int i = 0; i < second->numVertices; i++) {
+        Vector2 normal = second->edges[i].normal;
+
+        Vector2 firstProj = getProjection(first->transformedVertices, first->numVertices, normal);
+        Vector2 secondProj = getProjection(second->transformedVertices, second->numVertices, normal);
+
+        if (!projectionsOverlap(firstProj, secondProj)) {
+            return false;
+        }
+    }
+
+    return true;
+}