Line collision in pygame

// Moving box 2 box intercepts var objBox = createBox(0, 0, 0, 0); // the moving box var objLine = createLine(0, 0, 0, 0); // the line representing the box movement var boxes = []; // array of boxes to check against //Find closest intercept to start of line function findIntercepts(B, L) { lineAddSlopes(L); // get slopes and extras for line (one off calculation) // for each obstacles check for intercept; for (var i = 0; i < boxes.length; i++) { intercept(B, L, boxes[i]); } // Line will hold the intercept pos as minX, minY, the normals of the side hit in nx,ny // and the dist from the line start squared } function lineAddSlopes(l) { // adds the slopes of the lie for x,y and length as dist var dx = l.x2 - l.x1; // vector from start to end of line var dy = l.y2 - l.y1; var dist = dx * dx + dy * dy; l.dx = dx / dy; // slope of line in terms of y to find x l.dy = dy / dx; // slope of line in terms of x to find y l.dist = dist; l.minX = dx; // the 2D intercept point. l.minY = dy; l.nx = 0; // the face normal of the intercept point l.ny = 0; } function intercept(moveBox, moveLine, obstructionBox) { // find the closest intercept, if any var check, iPosX, iPosY, distSqrX, distSqrY; const b1 = moveBox, b2 = obstructionBox, l = moveLine; distSqrX = distSqrY = l.dist; const lr = l.x1 < l.x2; // lr for (l)eft to (r)ight is true is line moves from left to right. const tb = l.y1 < l.y2; // tb for (t)op to (b)ottom is true is line moves from top to bottom const w2 = b1.w / 2, h2 = b1.h / 2; const right = b2.x + b2.w + w2; const left = b2.x - w2; const top = b2.y - h2; const bottom = b2.y + b2.h + h2; check = lr ? // quick check if collision is possible l.x1 < right && l.x2 > left: l.x2 < right && l.x1 > left; check && (check = tb ? l.y1 < bottom && l.y2 > top: l.y2 < bottom && l.y1 > top); if (check) { const lrSide = lr ? left : right; // get closest left or right side const tbSide = tb ? top : bottom; // get closest top or bottom side const distX = lrSide - l.x1; // x Axis distance to closest side const distY = tbSide - l.y1; // y Axis distance to closest side iPosX = l.x1 + distY * l.dx; // X intercept of top or bottom iPosY = l.y1 + distX * l.dy; // Y intercept of left or right if (iPosX >= left && iPosX <= right) { // is there a x Axis intercept? iPosX -= l.x1; distSqrX = Math.min(distSqrX, distY * distY + iPosX * iPosX); // distance squared } if (iPosY >= top && iPosY <= bottom) { // is there a y Axis intercept? iPosY -= l.y1; distSqrY = Math.min(distSqrY, distX * distX + iPosY * iPosY); } if (distSqrX < l.dist || distSqrY < l.dist) { if (distSqrX < distSqrY) { l.dist = distSqrX; l.minX = iPosX; l.minY = distY; l.nx = 0; l.ny = tb ? -1 : 1; } else { l.dist = distSqrY; l.minX = distX; l.minY = iPosY; l.nx = lr ? -1 : 1; l.ny = 0; } l.x2 = l.x1 + l.minX; // Set new line end. This keeps the line l.y2 = l.y1 + l.minY; // length as short as possible and avoid // unnneeded intercept tests } } } //====================================================================================================================== // SUPPORT CODE FROM HERE DOWN //====================================================================================================================== // The following code is support code that provides me with a standard interface to various forums. // It provides a mouse interface, a full screen canvas, and some global often used variable // like canvas, ctx, mouse, w, h (width and height), globalTime // This code is not intended to be part of the answer unless specified and has been formated to reduce // display size. It should not be used as an example of how to write a canvas interface. // By Blindman67 const RESIZE_DEBOUNCE_TIME = 100; var w, h, cw, ch, canvas, ctx, onResize, mouse, createCanvas, resizeCanvas, setGlobals, globalTime = 0, resizeCount = 0; createCanvas = function () { var c, cs; cs = (c = document.createElement("canvas")).style; cs.position = "absolute"; cs.top = cs.left = "0px"; cs.zIndex = 1000; document.body.appendChild(c); return c; } resizeCanvas = function () { if (canvas === undefined) { canvas = createCanvas(); } canvas.width = window.innerWidth; canvas.height = window.innerHeight; ctx = canvas.getContext("2d"); if (typeof setGlobals === "function") { setGlobals(); } if (typeof onResize === "function") { resizeCount += 1; setTimeout(debounceResize, RESIZE_DEBOUNCE_TIME); } } function debounceResize() { resizeCount -= 1; if (resizeCount <= 0) { onResize(); } } setGlobals = function () { cw = (w = canvas.width) / 2; ch = (h = canvas.height) / 2; mouse.updateBounds(); } mouse = (function () { function preventDefault(e) { e.preventDefault(); } var mouse = { x : 0, y : 0, w : 0, alt : false, shift : false, ctrl : false, buttonRaw : 0, over : false, bm : [1, 2, 4, 6, 5, 3], active : false, bounds : null, crashRecover : null, mouseEvents : "mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".split(",") }; var m = mouse; function mouseMove(e) { var t = e.type; m.x = e.clientX - m.bounds.left; m.y = e.clientY - m.bounds.top; m.alt = e.altKey; m.shift = e.shiftKey; m.ctrl = e.ctrlKey; if (t === "mousedown") { m.buttonRaw |= m.bm[e.which - 1]; } else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2]; } else if (t === "mouseout") { !m.buttonRaw && (m.over = false); } else if (t === "mouseover") { m.over = true; } else if (t === "mousewheel") { m.w = e.wheelDelta; } else if (t === "DOMMouseScroll") { m.w = -e.detail; } e.preventDefault(); } m.updateBounds = function () { if (m.active) { m.bounds = m.element.getBoundingClientRect(); } } m.addCallback = function (callback) { if (typeof callback === "function") { if (m.callbacks === undefined) { m.callbacks = [callback]; } else { m.callbacks.push(callback); } } else { throw new TypeError("mouse.addCallback argument must be a function"); } } m.start = function (element, blockContextMenu) { if (m.element !== undefined) { m.removeMouse(); } m.element = element === undefined ? document : element; m.blockContextMenu = blockContextMenu === undefined ? false : blockContextMenu; m.mouseEvents.forEach(n => { document.addEventListener(n, mouseMove); }); if (m.blockContextMenu === true) { m.element.addEventListener("contextmenu", preventDefault, false); } m.active = true; m.updateBounds(); } m.remove = function () { if (m.element !== undefined) { m.mouseEvents.forEach(n => { m.element.removeEventListener(n, mouseMove); }); if (m.contextMenuBlocked === true) { m.element.removeEventListener("contextmenu", preventDefault); } m.element = m.callbacks = m.contextMenuBlocked = undefined; m.active = false; } } return mouse; })(); resizeCanvas(); mouse.start(canvas, true); window.addEventListener("resize", resizeCanvas); w = canvas.width; h = canvas.height; cw = w / 2; // center ch = h / 2; globalTime = new Date().valueOf(); // global to this var numRandomBoxes = 10; // number of obstacles var movePoint = 0; // which end of the line to move var boxes = []; // array of boxes. onresize = function(){ boxes = []; numRandomBoxes = Math.floor(((w * h) / (30*130)) * 0.25); // approx box density of 1/8th canvas pixels boxes.push(createBox(0,h-100,w,10)); // create a ground box var i = 0; // create some random boxes while(i++ < numRandomBoxes){ boxes.push(createBox(rand(-10,w + 10),rand(-10,h + 10),rand(10,30),rand(10,130))); } } onresize(); // set up var objBoxE = createBox(0,0,0,0); // a mirror of moving used for display var boxSizing = false; function createBox(x, y, w, h) { return { x : x, y : y, w : w, h : h}; } function createLine(x1, y1, x2, y2) { return { x1 : x1, y1 : y1, x2 : x2, y2 : y2}; } function copyBox(b1, b2) { // copy coords from b1 to b2 b2.x = b1.x; b2.y = b1.y; b2.w = b1.w; b2.h = b1.h; } function rand(min, max) { // returns a random int between min and max inclusive return Math.floor(Math.random() * (max - min) + min); } // draw a box function drawBox(b, ox = 0, oy = 0, xx = 0, yy = 0, fill) { // ox,oy optional expand box. if (!fill) { ctx.strokeRect(b.x - ox + xx, b.y - oy + yy, b.w + ox * 2, b.h + oy * 2); } else { ctx.fillRect(b.x - ox + xx, b.y - oy + yy, b.w + ox * 2, b.h + oy * 2); } } // draw a line function drawLine(l, ox, oy) { // ox and oy optional offsets ox = ox ? ox : 0; oy = oy ? oy : 0; ctx.moveTo(l.x1 + ox, l.y1 + oy) ctx.lineTo(l.x2 + ox, l.y2 + oy); } // draw a a cross (mark) function drawMark(x, y, size) { ctx.fillRect(x - size / 2, y - 0.5, size, 1); ctx.fillRect(x - 0.5, y - size / 2, 1, size); } // main update function function update(timer){ requestAnimationFrame(update); var L,B; // short cuts to line and box to make code readable L = objLine; B = objBox; globalTime = timer; ctx.setTransform(1,0,0,1,0,0); // reset transform ctx.globalAlpha = 1; // reset alpha ctx.clearRect(0,0,w,h); if(mouse.buttonRaw & 4){ // right button to clear the box and line B.x = B.y = 0; B.w = B.h = 0; L.x1 = L.x2 = 0; L.y1 = L.y2 = 0; copyBox(B,objBoxE); } if(mouse.buttonRaw & 1){ // if left button drag new box or move line ends if(B.w === 0){ // if the box has no size boxSizing = true; // create a box and flag that we are sizing the box B.x = mouse.x; B.y = mouse.y; B.w = 1; B.h = 1; }else{ if(boxSizing){ // drag out the box size B.x = Math.min(mouse.x,B.x); B.y = Math.min(mouse.y,B.y); B.w = Math.max(1,mouse.x-B.x); B.h = Math.max(1,mouse.y-B.y); }else{ if(L.x1 === L.x2 && L.y1 === L.y2 ){ // else if line does not exist start a new one movePoint = 1; L.x1 = B.x + B.w / 2; L.y1 = B.y + B.h / 2; L.x2 = mouse.x + 1; L.y2 = mouse.y + 1; }else{ // if line does exist find closest end if(mouse.oldBRaw !== mouse.buttonRaw){ // mouse button just down movePoint = 1; } L.x2 = mouse.x; L.y2 = mouse.y; } B.x = L.x1 - B.w / 2; B.y = L.y1 - B.h / 2; objBoxE.x = L.x2 - B.w / 2; objBoxE.y = L.y2 - B.h / 2; objBoxE.w = B.w; objBoxE.h = B.h; } } }else{ boxSizing = false; } // draw obstical boxes ctx.strokeStyle = "black"; for(var i = 0; i < boxes.length; i ++){ drawBox(boxes[i]); } // draw start and end boxes ctx.strokeStyle = "red" drawBox(B); drawBox(objBoxE); // draw the line ctx.beginPath(); drawLine(L); ctx.stroke(); // draw the box outer edges ctx.globalAlpha = 0.25; ctx.beginPath(); drawLine(L,-B.w/2,-B.h/2); drawLine(L,B.w/2,-B.h/2); drawLine(L,B.w/2,B.h/2); drawLine(L,-B.w/2,B.h/2); ctx.stroke(); // if the line has length then check for intercepts if(!(L.x1 === L.x2 && L.y1 === L.y2 )){ ctx.strokeStyle = "Blue" findIntercepts(B,L); ctx.fillStyle = "#0F0"; ctx.strokeStyle = "black" ctx.globalAlpha = 0.2; drawBox(B,0,0,0,0,true); drawBox(B); ctx.globalAlpha = 1; drawBox(B,0,0,L.minX,L.minY,true); drawBox(B,0,0,L.minX,L.minY); ctx.beginPath(); ctx.moveTo(L.x1 + L.minX, L.y1 + L.minY); ctx.lineTo(L.x1 + L.minX+ L.nx * 30, L.y1 + L.minY+ L.ny * 30); ctx.stroke(); } if(mouse.buttonRaw === 0){ ctx.globalAlpha = 1; ctx.font = "16px arial"; ctx.textAlign = "center"; ctx.fillStyle = "rgba(240,230,220,0.8)"; ctx.strokeStyle = "black" ctx.fillRect(20,h - 42, w- 40,40); ctx.strokeRect(20,h - 42, w- 40,40); ctx.fillStyle = "black" if(B.w === 0){ ctx.fillText("Left click drag to size a box",w / 2, h - 20); ctx.canvas.style.cursor = "crosshair"; }else if(!(L.x1 === L.x2 && L.y1 === L.y2 )){ ctx.fillText("Left click drag to move box destination",w / 2, h - 26); ctx.fillText("Right click to clear.",w / 2, h - 6); ctx.canvas.style.cursor = "move"; }else{ ctx.fillText("Left click drag to move box destination",w / 2, h - 26); ctx.fillText("Right click to clear.",w / 2, h - 6); ctx.canvas.style.cursor = "move"; } } else { ctx.canvas.style.cursor = "none"; } mouse.oldBRaw = mouse.buttonRaw; } requestAnimationFrame(update);