Terrain and tanks

terrain.js

@@ -1,13 +1,18 @@
-import {createCanvas, drawRect, clipCanvas} from './gfx.js';
+import {createCanvas, drawRect, clipCanvas, plot} from './gfx.js';
+import {randomInt} from './math.js';
 
 export function createTerrain(width, height) {
   const terrain = createCanvas(width, height);
-  generateTerrain(terrain, width, height);
+  generateTerrain(terrain);
   return terrain;
 }
 
-export function generateTerrain(ctx, width, height) {
-  drawRect(ctx, 0, height-80, width, 80, 'burlywood');
+export function generateTerrain(ctx) {
+  const {width, height} = ctx.canvas;
+  for (let x=0; x<width; x++) {
+    const h = Math.round(80 + 8 * Math.sin(x/25));
+    drawRect(ctx, x, height-h, 1, h, 'burlywood');
+  }
 }
 
 export function isTerrain(ctx, x, y) {
@@ -15,6 +20,14 @@ export function isTerrain(ctx, x, y) {
   return imageData.data[3] > 0;
 }
 
+export function landHeight(ctx, x) {
+  const {height} = ctx.canvas;
+  const imageData = ctx.getImageData(x, 0, 1, height);
+  for (let y=height-1; y>=0; y--) {
+    if (imageData.data[y*4+3] === 0) return y;
+  }
+}
+
 export function clipTerrain(ctx, fn) {
   return clipCanvas(ctx, fn);
 }