3 files changed, 211 insertions, 0 deletions
diff --git a/frontend/_shared/math/circle.js b/frontend/_shared/math/circle.js
new file mode 100644
index 0000000..340d7dc
--- /dev/null
+++ b/frontend/_shared/math/circle.js
@@ -0,0 +1,112 @@
+/// <reference path="mat4.js" />
+/// <reference path="vec2.js" />
+
+const BYTES_PER_FLOAT = 4;
+
+/**
+ * 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);
+
+    var lBufferedData = [];
+    vertexCount = 0;
+
+    const lAngleIncrements = (360.0 / pSegments) * (Math.PI / 180.0);
+    for (let lSegIdx = 0; lSegIdx < pSegments; lSegIdx++) {
+        const lAngle = lAngleIncrements * lSegIdx,
+            lNextAngle = lAngleIncrements * (lSegIdx + 1),
+            lColorIndex = Math.floor(pColorList.length * (lSegIdx / pSegments)),
+            lColor = pColorList[lColorIndex]; // TODO: Calculate which one to use
+
+        lBufferedData = lBufferedData.concat([
+            0,                              0,                              lColor.x, lColor.y, lColor.z, lColor.w,
+            pRadius * Math.sin(lAngle),     pRadius * Math.cos(lAngle),     lColor.x, lColor.y, lColor.z, lColor.w,
+            pRadius * Math.sin(lNextAngle), pRadius * Math.cos(lNextAngle), lColor.x, lColor.y, lColor.z, lColor.w
+        ]);
+
+        vertexCount += 3;
+    }
+
+    pGl.bufferData(pGl.ARRAY_BUFFER, new Float32Array(lBufferedData), pGl.STATIC_DRAW)
+    pGl.bindBuffer(pGl.ARRAY_BUFFER, undefined);
+
+    return { 
+        buffer: lBuffer, 
+        vertexCount: vertexCount,
+        prevPos: vec2(),
+        position: pInitialPosition || vec2(),
+        prevVelocity: vec2(),
+        velocity: vec2(),
+        force: vec2(),
+        torque: 0,
+        mass: pMass === undefined ? 1 : pMass,
+        rotationVelocity: 0,
+        rotationRadians: 0,
+        model: translateMatrix(mat4(), pInitialPosition ? pInitialPosition.x : 0, pInitialPosition ? pInitialPosition.y : 0, 0),
+        radius: pRadius
+    };
+}
+
+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);
+        pGl.vertexAttribPointer(pProgramInfo.attributeLocations.position, 2, pGl.FLOAT, false, BYTES_PER_FLOAT * 6, 0);
+
+        pGl.enableVertexAttribArray(pProgramInfo.attributeLocations.color);
+        pGl.vertexAttribPointer(pProgramInfo.attributeLocations.color, 4, pGl.FLOAT, false, BYTES_PER_FLOAT * 6, BYTES_PER_FLOAT * 2);
+    }
+
+    pGl.drawArrays(pGl.TRIANGLE_STRIP, 0, pCircle.vertexCount);
+}
+
+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));
+    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)
+    );
+
+    return {
+        relativeVelocity:   subVec2(pFirst.velocity, pSecond.velocity),
+        collisionNormal:    lCollisionNormal,
+        //firstPointOfApplication: addVec2(scaleVec2(normalize2(pFirst.velocity), pFirst.radius), pFirst.position),
+        //secondPointOfApplication: addVec2(scaleVec2(normalize2(pSecond.velocity), pSecond.radius), pSecond.position)
+        firstPointOfApplication: subVec2(lCollisionPoint, pFirst.position),
+        secondPointOfApplication: subVec2(lCollisionPoint, pSecond.position)
+    }
+}
+
+function freeCircle(pGl, pCircle) {
+    pGl.deleteBuffer(pCircle.buffer);
+}
+\ No newline at end of file
diff --git a/frontend/_shared/math/mat4.js b/frontend/_shared/math/mat4.js
new file mode 100644
index 0000000..6ab29e2
--- /dev/null
+++ b/frontend/_shared/math/mat4.js
@@ -0,0 +1,43 @@
+function mat4() {
+    return [
+        1, 0, 0, 0,
+        0, 1, 0, 0,
+        0, 0, 1, 0,
+        0, 0, 0, 1
+    ]
+}
+
+function orthographic(pLeft, pRight, pBottom, pTop) {
+    const lResult = mat4();
+    lResult[0] = 2.0 / (pRight - pLeft);
+    lResult[5] = 2.0 / (pTop - pBottom);
+    lResult[10] = 1.0;
+    lResult[12] = -(pRight + pLeft) / (pRight - pLeft);
+    lResult[13] = -(pTop + pBottom) / (pTop - pBottom);
+    return lResult;
+}
+
+function translateMatrix(m, x, y, z) {
+    m = [...m];
+    m[12] += x;
+    m[13] += y;
+    m[14] += z;
+    return m;
+}
+
+function rotateMatrix2d(m, angle) {
+    m = [...m];
+    m[0] = Math.cos(angle);
+    m[1] = -Math.sin(angle);
+    m[4] = Math.sin(angle);
+    m[5] = Math.cos(angle);
+    return m;
+}
+
+function scaleMatrix(m, x, y, z) {
+    m = [...m];
+    m[0] = m[0] * x;
+    m[5] = m[5] * y;
+    m[10] = m[10] * z;
+    return m;
+}
+\ No newline at end of file
diff --git a/frontend/_shared/math/vec2.js b/frontend/_shared/math/vec2.js
new file mode 100644
index 0000000..cff38ce
--- /dev/null
+++ b/frontend/_shared/math/vec2.js
@@ -0,0 +1,56 @@
+function vec2(x = 0, y = 0) {
+    return { x: x, y: y};
+}
+
+function addVec2(v1, v2) {
+    return {
+        x: v1.x + v2.x,
+        y: v1.y + v2.y
+    };
+}
+
+function subVec2(v1, v2) {
+    return {
+        x: v1.x - v2.x,
+        y: v1.y - v2.y
+    };
+}
+
+function scaleVec2(v, s) {
+    return {
+        x: v.x * s,
+        y: v.y * s
+    };
+}
+
+function dot2(v1, v2) {
+    return v1.x * v2.x + v1.y * v2.y;
+}
+
+function length2(v) {
+    return Math.sqrt(v.x * v.x + v.y * v.y);
+}
+
+function normalize2(v) {
+    const lLength = length2(v);
+    const lInverseLength = lLength === 0 ? 1.0 : 1.0 / length2(v);
+    return { x: v.x * lInverseLength, y: v.y * lInverseLength };
+}
+
+function vec2str(v) {
+    return `(${v.x.toFixed(2)}, ${v.y.toFixed(2)})`;
+}
+
+function getPerp2(v) {
+    return {
+        x: -v.y,
+        y: v.x
+    };
+}
+
+function negate2(v) {
+    return {
+        x: -v.x,
+        y: -v.y
+    };
+}
+\ No newline at end of file