From d644eff20a20809dffbb098b2e74dbd4c1ef5fb9 Mon Sep 17 00:00:00 2001 From: Matthew Kosarek Date: Sun, 11 Apr 2021 16:35:25 -0400 Subject: Nearly have good pill-lin collisions working, just need to get the actual equation right --- frontend/2d/_collisions/pill_line.html | 18 +++- frontend/2d/_collisions/pill_line.html.content | 15 ++++ frontend/2d/_collisions/pill_line/dist/output.wasm | Bin 57400 -> 60622 bytes frontend/2d/_collisions/pill_line/main.cpp | 98 ++++++++++++++++++--- 4 files changed, 115 insertions(+), 16 deletions(-) diff --git a/frontend/2d/_collisions/pill_line.html b/frontend/2d/_collisions/pill_line.html index 4cbefde..8b3539a 100644 --- a/frontend/2d/_collisions/pill_line.html +++ b/frontend/2d/_collisions/pill_line.html @@ -47,6 +47,21 @@ +

Pill-Line

@@ -72,7 +87,6 @@
-
  • -  +don diff --git a/frontend/2d/_collisions/pill_line.html.content b/frontend/2d/_collisions/pill_line.html.content index fb2994c..c534d93 100644 --- a/frontend/2d/_collisions/pill_line.html.content +++ b/frontend/2d/_collisions/pill_line.html.content @@ -1,4 +1,19 @@ +

    Pill-Line

    diff --git a/frontend/2d/_collisions/pill_line/dist/output.wasm b/frontend/2d/_collisions/pill_line/dist/output.wasm index 3b6a673..c671a7e 100755 Binary files a/frontend/2d/_collisions/pill_line/dist/output.wasm and b/frontend/2d/_collisions/pill_line/dist/output.wasm differ diff --git a/frontend/2d/_collisions/pill_line/main.cpp b/frontend/2d/_collisions/pill_line/main.cpp index 76dc7d4..0476b98 100644 --- a/frontend/2d/_collisions/pill_line/main.cpp +++ b/frontend/2d/_collisions/pill_line/main.cpp @@ -19,6 +19,8 @@ struct Rigidbody { float32 rotationalVelocity = 0.f; float32 rotation = 0.f; float32 mass = 1.f; + float32 cofOfRestition = 0.7f; + float32 momentOfInertia = 0.f; void reset() { force = { 0, 0 }; @@ -41,6 +43,10 @@ struct Rigidbody { rotation += (rotationalVelocity * deltaTimeSeconds); } + + void setMomentOfInertia(float32 moi) { + momentOfInertia = moi; + } }; struct Pill { @@ -95,6 +101,9 @@ struct Pill { shape.load(vertices, numVertices, renderer); body.reset(); + // https://byjus.com/jee/moment-of-inertia-of-ellipse/ + body.momentOfInertia = (body.mass * (a * a + b * b)) / 4.f; + a = width / 2.f; b = height / 2.f; @@ -121,20 +130,30 @@ struct Pill { struct LineSegment { OrthographicShape shape; + Rigidbody body; Vector2 start; Vector2 end; + float32 length; Vector2 normal; OrthographicVertex vertices[2]; void load(OrthographicRenderer* renderer, Vector4 color, Vector2 inStart, Vector2 inEnd) { start = inStart; end = inEnd; + length = (start - end).length(); vertices[0].position = start; vertices[0].color = color; vertices[1].position = end; vertices[1].color = color; normal = (end - start).getPerp().normalize(); shape.load(vertices, 2, renderer); + + body.reset(); + body.mass = 100000.f; + body.cofOfRestition = 1.f; + body.rotationalVelocity = 0; + body.velocity = Vector2(); + body.momentOfInertia = body.mass * (length / 2.f); } void render(OrthographicRenderer* renderer) { @@ -159,9 +178,10 @@ struct LineSegment { struct IntersectionResult { bool intersect = false; - Vector2 pointOfIntersection; Vector2 collisionNormal; Vector2 relativeVelocity; + Vector2 firstPointOfApplication; + Vector2 secondPointOfApplication; }; EM_BOOL onPlayClicked(int eventType, const EmscriptenMouseEvent* mouseEvent, void* userData); @@ -209,6 +229,34 @@ float32 areaOfTriangle(Vector2 a, Vector2 b, Vector2 c) { IntersectionResult getIntersection(Pill* pill, LineSegment* segment) { IntersectionResult result; + + /** + + Formula for finding equation of pill: + 1) Using the parametrized equation of a line: + x(t) = x1 + (x2 - x1) * t + y(t) = y1 + (y2 - y1) * t + 2) Knowing the equation of a translated and rotated ellipse: + + Define x and y as follows: + + x = x_1 + l, where l is the translation in x + y = y_1 + h, where h is the translation in y + + Therefore, the general equation of a rotated ellipse is: + + (x * cos(theta) + y * sin(theta)) / (a * a) + + (y * cos(theta) - x * sin(theta)) / b * b = 1 + + ( + l + x * cos(theta) + y * sin(theta)) / (a * a) + + (y + h + y * cos(theta) + y * sin(theta)) / (a * a) + + 3) Plug in the parametrized equation of our line for x_1 and y_2. + + 4) If the determinant >= 0, we have an intersection, otherwise, nothing. + + **/ + /*float32 rotationAngleOfPill = pill->body.rotation; Vector2 translationOfPill = pill->body.position; @@ -249,20 +297,37 @@ IntersectionResult getIntersection(Pill* pill, LineSegment* segment) { float32 t1 = -B + determinant / (2 * A); float32 t2 = -B - determinant / (2 * A); - Vector2 pointAtT1 = { segment->start.x + (t1 * (segment->end.x - segment->start.x)), segment->start.y + (t1 * (segment->end.y - segment->start.y)) }; + Vector2 pointAtT1 = pill->shape.model * Vector2 { segment->start.x + (t1 * (segment->end.x - segment->start.x)), segment->start.y + (t1 * (segment->end.y - segment->start.y)) }; Vector2 pointAtT2 = { segment->start.x + (t2 * (segment->end.x - segment->start.x)), segment->start.y + (t2 * (segment->end.y - segment->start.y)) }; - printf("Intersecting\n"); result.intersect = true; - result.pointOfIntersection = pointAtT1 - pill->body.position;; - result.relativeVelocity = Vector2() - pill->body.velocity; + result.relativeVelocity = pill->body.velocity - segment->body.velocity;; result.collisionNormal = (pointAtT1 - pill->body.position).normalize(); + result.firstPointOfApplication = pointAtT1 - pill->body.position; + result.secondPointOfApplication = pointAtT1 - ((segment->end - segment->start) / 2.f); return result; } void resolveCollision(Rigidbody* first, Rigidbody* second, IntersectionResult* ir) { - + Vector2 relativeVelocity = ir->relativeVelocity; + Vector2 collisionNormal = ir->collisionNormal; + Vector2 firstPerp = ir->firstPointOfApplication.getPerp(); + Vector2 secondPerp = ir->secondPointOfApplication.getPerp(); + + float32 cofOfRestition = (first->cofOfRestition + second->cofOfRestition) / 2.f; + float32 lNumerator = (relativeVelocity * -(1.0 + cofOfRestition)).dot(collisionNormal); + float32 lLinearDenomPart = collisionNormal.dot(collisionNormal * (1 / first->mass + 1 / second->mass)); + float32 lRotationalDenomPart = powf(firstPerp.dot(collisionNormal), 2) / first->momentOfInertia + + powf(secondPerp.dot(collisionNormal), 2) / second->momentOfInertia; + + float32 lImpulseMagnitude = lNumerator / (lLinearDenomPart);// + lRotationalDenomPart); + + first->velocity = first->velocity + (collisionNormal * (lImpulseMagnitude / first->mass)); + second->velocity = second->velocity - (collisionNormal * (lImpulseMagnitude / second->mass)); + + //first->rotationalVelocity = first->rotationalVelocity + firstPerp.dot(collisionNormal * lImpulseMagnitude) / first->momentOfInertia; + //second->rotationalVelocity = second->rotationalVelocity - secondPerp.dot(collisionNormal * lImpulseMagnitude) / second->momentOfInertia; } void update(float32 deltaTimeSeconds, void* userData) { @@ -280,20 +345,25 @@ void update(float32 deltaTimeSeconds, void* userData) { if (ir.intersect) { // Find the exact moment that the intersection happens by rewinding the simulation until we're not intersecting - while (ir.intersect) { - pill = copyPill.copy(); - deltaTimeSeconds /= 2.f; - pill.update(deltaTimeSeconds); + IntersectionResult subIr = ir; + float32 subdividedTimeSeconds = deltaTimeSeconds; + do { + ir = subIr; - ir = getIntersection(&pill, &segmentList[lineIdx]); + pill = copyPill.copy(); + subdividedTimeSeconds /= 2.f; + pill.update(subdividedTimeSeconds); - if (deltaTimeSeconds <= 0.f) { + subIr = getIntersection(&pill, &segmentList[lineIdx]); + if (subdividedTimeSeconds == 0.f) { printf("Error: Should not be happening.\n"); break; } - } + } while (subIr.intersect); - printf("Found intersection at timestamp: %f\n", deltaTimeSeconds); + printf("Found intersection at timestamp: %f\n", subdividedTimeSeconds); + resolveCollision(&pill.body, &segmentList[lineIdx].body, &ir); + pill.update(deltaTimeSeconds - subdividedTimeSeconds); } } -- cgit v1.2.1