1 files changed, 51 insertions, 2 deletions

diff --git a/frontend/_rigidbody/circle.js b/frontend/_rigidbody/circle.js
index 194a772..35044e3 100644
--- a/frontend/_rigidbody/circle.js
+++ b/frontend/_rigidbody/circle.js
@@ -1,6 +1,16 @@
 const BYTES_PER_FLOAT = 4;
 
-function circle(pGl, pRadius, pSegments, pColorList, pInitialPosition) {
+/**
+ * Initializes a new circle object for the WebGL context.
+ * 
+ * @param {WebGLRenderingContext} pGl 
+ * @param {number} pRadius 
+ * @param {number} pSegments 
+ * @param {Array<Vector4>} pColorList 
+ * @param {vec2} pInitialPosition 
+ * @param {number} pMass 
+ */
+function circle(pGl, pRadius, pSegments, pColorList, pInitialPosition, pMass) {
     const lBuffer = pGl.createBuffer();
 
     pGl.bindBuffer(pGl.ARRAY_BUFFER, lBuffer);
@@ -30,11 +40,12 @@ function circle(pGl, pRadius, pSegments, pColorList, pInitialPosition) {
     return { 
         buffer: lBuffer, 
         vertexCount: vertexCount,
+        prevPos: vec2(),
         position: pInitialPosition || vec2(),
         velocity: vec2(),
         force: vec2(),
         torque: 0,
-        mass: 1,
+        mass: pMass || 1,
         rotationVelocity: 0,
         rotationRadians: 0,
         model: mat4(),
@@ -43,6 +54,7 @@ function circle(pGl, pRadius, pSegments, pColorList, pInitialPosition) {
 }
 
 function renderCircle(pGl, pProgramInfo, pCircle) {
+    pGl.uniformMatrix4fv(pProgramInfo.uniformLocations.model, false, pCircle.model);
     pGl.bindBuffer(pGl.ARRAY_BUFFER, pCircle.buffer);
     {
         pGl.enableVertexAttribArray(pProgramInfo.attributeLocations.position);
@@ -57,4 +69,41 @@ function renderCircle(pGl, pProgramInfo, pCircle) {
 
 function getMomentOfInertia(pCircle) {
     return (Math.PI * Math.pow(pCircle.radius, 4)) / 4;
+}
+
+function doCirclesIntersect(pFirst, pSecond) {
+    const lDistanceBetween = Math.pow(pFirst.position.x - pSecond.position.x, 2) 
+        + Math.pow(pFirst.position.y - pSecond.position.y, 2)
+    return lDistanceBetween <= Math.pow(pFirst.radius + pSecond.radius, 2);
+}
+
+/**
+ * Returns intersection information about the intersecting circles.
+ * 
+ * Warning! Only use this if doCirclesIntersect returned true for these circles.
+ * 
+ * @param {circle} pFirst 
+ * @param {circle} pSecond 
+ */
+function getIntersectionDataForCircles(pFirst, pSecond) {
+    // The collision normal is simply the difference between the two current positions
+    const lCollisionNormal = normalize2(subVec2(pFirst.position, pSecond.position));
+
+    // TODO: Might be useful in the future?
+    const lCollisionPoint = vec2(
+        ((pFirst.position.x * pSecond.radius) + (pSecond.position.x * pFirst.radius)) / (pFirst.radius + pSecond.radius),
+        ((pFirst.position.y * pSecond.radius) + (pSecond.position.y * pFirst.radius))  / (pFirst.radius + pSecond.radius)
+    );
+
+    const lSecondDeepestPointInFirst = (subVec2(pSecond.position, scaleVec2(lCollisionNormal, pSecond.radius)));
+    const lFirstDeepestPointInSecond = (addVec2(pFirst.position, scaleVec2(lCollisionNormal, pFirst.radius)));
+    const lLengthOfOverlapByTwo = length2(subVec2(lFirstDeepestPointInSecond, lSecondDeepestPointInFirst)) / 2.0;
+    const lMedianIntersectingPoint = addVec2(lSecondDeepestPointInFirst, scaleVec2(lCollisionNormal, lLengthOfOverlapByTwo));
+
+    return {
+        relativeVelocity:   subVec2(pFirst.velocity, pSecond.velocity),
+        collisionNormal:    lCollisionNormal,
+        firstPointOfApplication: subVec2(lMedianIntersectingPoint, pFirst.position),
+        secondPointOfApplication: subVec2(lMedianIntersectingPoint, pSecond.position)
+    }
 }
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