Close to being done on line-circle collisions, but it appears we're running into a rotation problem. Going to work on square-line collisions in the meantime

6 files changed, 129 insertions, 15 deletions

diff --git a/frontend/_shared/math/circle.js b/frontend/_shared/math/circle.js
index 340d7dc..ba33021 100644
--- a/frontend/_shared/math/circle.js
+++ b/frontend/_shared/math/circle.js
@@ -71,7 +71,7 @@ function renderCircle(pGl, pProgramInfo, pCircle) {
     pGl.drawArrays(pGl.TRIANGLE_STRIP, 0, pCircle.vertexCount);
 }
 
-function getMomentOfInertia(pCircle) {
+function getCircleMomentOfInertia(pCircle) {
     return (Math.PI * Math.pow(pCircle.radius, 4)) / 4;
 }
 
diff --git a/frontend/_shared/math/collision.js b/frontend/_shared/math/collision.js
index 74ec5d8..8e4be7d 100644
--- a/frontend/_shared/math/collision.js
+++ b/frontend/_shared/math/collision.js
@@ -2,22 +2,25 @@
 /// <reference path="line2.js" />
 /// <reference path="circle.js" />
 /// <reference path="mat4.js" />
+/// <reference path="point2.js" />
 
 /**
  * 
- * @param {circle} pCricle 
+ * @param {circle} pCircle 
  * @param {line2} pLine 
  */
-function lineCircleCollision2(pCricle, pLine) {
-    // We have a triangle formed by circle's position P and the two points of the line, A and B.
-    var lSlope = (pCricle.position.y - pLine.start.y) / (pCricle.position.x - pLine.start.x),
-        lAngle = Math.atan(lSlope),
-        lAngleDiff = lAngle - pLine.angle,
-        lPositionToStart = subVec2(pCricle.position, pLine.start),
-        lPosToStartLength = length2(lPositionToStart),
-        lHeight = lPosToStartLength * Math.sin(lAngleDiff);
+function lineCircleCollision2(pCircle, pLine) {
+    return distanceFromPoint2ToLine2(pCircle.position, pLine) <= pCircle.radius;
+}
 
-    if (Math.abs(lHeight - pCricle.radius) < pCricle.radius) {
-        console.log('Intersection');
+function getLineCircleCollison2Data(pCircle, pLine) {
+    const lCollisionNormal = pLine.normal,
+        lCollisionPoint = addVec2(pCircle.position, scaleVec2(negate2(lCollisionNormal), pCircle.radius));
+        
+    return {
+        relativeVelocity:           subVec2(pCircle.velocity, pLine.velocity),
+        collisionNormal:            lCollisionNormal,
+        firstPointOfApplication:    subVec2(lCollisionPoint, pCircle.position),
+        secondPointOfApplication:   subVec2(lCollisionPoint, pLine.start)
     }
 }
\ No newline at end of file
diff --git a/frontend/_shared/math/line2.js b/frontend/_shared/math/line2.js
index d8ab096..a9e72be 100644
--- a/frontend/_shared/math/line2.js
+++ b/frontend/_shared/math/line2.js
@@ -7,7 +7,7 @@
  * @param {vec2} pEnd 
  * @param {WebGLRenderingContext} pGl
  */
-function line2(pStart, pEnd, pGl, pColor, pThickness) {
+function line2(pStart, pEnd, pGl, pColor, pMass) {
     const lDiffVector = subVec2(pEnd, pStart);
 
     const lBuffer = pGl.createBuffer();
@@ -28,12 +28,18 @@ function line2(pStart, pEnd, pGl, pColor, pThickness) {
         start: pStart,
         end: pEnd,
         slope: lSlope,
-        angle: Math.atan(lSlope),
+        normal: normalize2(getPerp2(lDiffVector)),
         length: length2(lDiffVector),
-        direction: normalize2(lDiffVector)
+        mass: pMass,
+        direction: normalize2(lDiffVector),
+        velocity: vec2(0, 0)
     };
 }
 
+function getLine2MomentOfInertia(pLine) {
+    return (1.0 / 12.0) * pLine.mass * Math.pow(pLine.length, 2);
+}
+
 function renderLine2(pGl, pProgramInfo, pLine) {
     pGl.uniformMatrix4fv(pProgramInfo.uniformLocations.model, false, mat4()); // Model on a line is always default matrix
     pGl.bindBuffer(pGl.ARRAY_BUFFER, pLine.buffer);
diff --git a/frontend/_shared/math/point2.js b/frontend/_shared/math/point2.js
new file mode 100644
index 0000000..eeacd91
--- /dev/null
+++ b/frontend/_shared/math/point2.js
@@ -0,0 +1,16 @@
+function point2(x = 0, y = 0) {
+    return { x: x, y: y };
+}
+
+function distanceFromPoint2ToLine2(pPoint, pLine) {
+    // Check out this wikapedia article for more information:
+    // https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line
+    var x0 = pPoint.x,
+        y0 = pPoint.y,
+        x1 = pLine.start.x,
+        y1 = pLine.start.y,
+        x2 = pLine.end.x,
+        y2 = pLine.end.y;
+
+    return Math.abs((x2 - x1) * (y1 - y0) - (x1 - x0) * (y2 - y1)) / Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
+}
\ No newline at end of file
diff --git a/frontend/_shared/math/rectangle.js b/frontend/_shared/math/rectangle.js
new file mode 100644
index 0000000..c24fa12
--- /dev/null
+++ b/frontend/_shared/math/rectangle.js
@@ -0,0 +1,32 @@
+/// <reference path="rigidbody2.js" />
+
+function rectangle(pGl, pData) {
+    var lBuffer = pGl.createBuffer(),
+        lColor = pData.color || { x: 1, y: 0, z: 0, w: 1 };
+
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, lBuffer);
+
+    var lBufferedData = [
+        0,              0,              lColor.x, lColor.y, lColor.z, lColor.w,
+        0,              pData.height,   lColor.x, lColor.y, lColor.z, lColor.w,
+        pData.width,    pData.height,   lColor.x, lColor.y, lColor.z, lColor.w,
+        pData.width,    pData.height,   lColor.x, lColor.y, lColor.z, lColor.w,
+        pData.width,    0,              lColor.x, lColor.y, lColor.z, lColor.w,
+        0,              0,              lColor.x, lColor.y, lColor.z, lColor.w
+    ];
+
+    pGl.bufferData(pGl.ARRAY_BUFFER, new Float32Array(lBufferedData), pGl.STATIC_DRAW)
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, undefined);
+
+    pData.getMomentOfInertia = function() {
+        return Math.pow(pData.width * pData.height, 3.0) / 12.0;
+    };
+        
+    return makeRigidBody2({
+        vertexCount:    6,
+        buffer:         lBuffer, 
+        width:          pData.width,
+        height:         pData.height,
+        model:          translateMatrix(mat4(), pData.position ? pData.position.x : 0, pData.position ? pData.position.y : 0, 0),
+    }, pData);
+}
\ No newline at end of file
diff --git a/frontend/_shared/math/rigidbody2.js b/frontend/_shared/math/rigidbody2.js
new file mode 100644
index 0000000..0b18d0c
--- /dev/null
+++ b/frontend/_shared/math/rigidbody2.js
@@ -0,0 +1,57 @@
+/// <reference path="vec2.js" />
+/// <reference path="mat4.js" />
+/// <reference path="circle.js" />
+/// <reference path="line2.js" />
+/// <reference path="collision.js" />
+
+const GRAVITY = 9.8;
+const BYTES_PER_FLOAT = 4;
+
+/**
+ * 
+ * @param {Shape} pObject a 2D shape like a circle, rectangle, or line
+ * @param {Object} pData initial data for the rigidboy
+ */
+function makeRigidBody2(pObject, pData) {
+    pObject.velocity            = vec2();
+    pObject.prevVelocity        = pObject.velocity;
+    pObject.position            = pData.position || vec2();
+    pObject.prevPosition        = pObject.position;
+    pObject.force               = vec2();
+    pObject.rotationVelocity    = 0;
+    pObject.rotationRadians     = 0;
+    pObject.torque              = 0;
+    pObject.mass                = pData.mass !== undefined ? pData.mass : 1.0;
+    pObject.getMomentOfInertia  = pData.getMomentOfInertia;
+
+    return pObject;
+}
+
+function updateRigidBody2(pRigidbody, pDeltaTimeSeconds) {
+    applyForceRigidbody2(pRigidbody, vec2(0, -1.0 * (pRigidbody.mass * GRAVITY)));
+    const lCurrentAcceleration = scaleVec2(pRigidbody.force, 1.0 / pRigidbody.mass);
+    pRigidbody.prevVelocity = pRigidbody.velocity;
+    pRigidbody.velocity = addVec2(pRigidbody.velocity, scaleVec2(lCurrentAcceleration, pDeltaTimeSeconds));
+    pRigidbody.prevPos = { ...pRigidbody.position };
+    pRigidbody.position = addVec2(pRigidbody.position, scaleVec2(pRigidbody.velocity, pDeltaTimeSeconds));
+    pRigidbody.force = vec2();
+
+    const lMomentOfInertia =  pRigidbody.getMomentOfInertia(pRigidbody);
+    const lAngularAcceleration = pRigidbody.torque / lMomentOfInertia;
+    pRigidbody.rotationVelocity += lAngularAcceleration * pDeltaTimeSeconds;
+    pRigidbody.rotationRadians += pRigidbody.rotationVelocity * pDeltaTimeSeconds;
+    pRigidbody.torque = 0;
+
+    pRigidbody.model = rotateMatrix2d(translateMatrix(mat4(), pRigidbody.position.x, pRigidbody.position.y, 0), pRigidbody.rotationRadians);
+}
+
+function applyForceRigidbody2(pRigidbody, pForceVector, pPointOfApplication) {
+    if (pPointOfApplication !== undefined) {
+        const lOriginToPointOfApp = subVec2(vec2(), pPointOfApplication),
+            lPerpVec = vec2(-lOriginToPointOfApp.y, lOriginToPointOfApp.x);
+
+            pRigidbody.torque += TORQUE_MULTIPLIER * dot2(lPerpVec, pForceVector);
+    }
+
+    pRigidbody.force = addVec2(pRigidbody.force, pForceVector);
+}