/
helper.js
66 lines (55 loc) · 2.15 KB
/
helper.js
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var gl;
function isPowerOf2(value) {
return (value & (value - 1)) == 0;
}
function degToRad (deg) {
return deg * Math.PI / 180;
}
function radToDeg (rad) {
return rad * 180 / Math.PI;
}
// Initialize a texture and load an image.
// When the image finished loading copy it into the texture.
function loadTexture(url) {
const texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Because images have to be download over the internet
// they might take a moment until they are ready.
// Until then put a single pixel in the texture so we can
// use it immediately. When the image has finished downloading
// we'll update the texture with the contents of the image.
const level = 0;
const internalFormat = gl.RGBA;
const width = 1;
const height = 1;
const border = 0;
const srcFormat = gl.RGBA;
const srcType = gl.UNSIGNED_BYTE;
const pixel = new Uint8Array([0, 0, 255, 255]); // opaque blue
gl.texImage2D(gl.TEXTURE_2D, level, internalFormat,
width, height, border, srcFormat, srcType,
pixel);
const image = new Image();
image.onload = function() {
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, level, internalFormat,
srcFormat, srcType, image);
// disable bilinear filtering!
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// WebGL1 has different requirements for power of 2 images
// vs non power of 2 images so check if the image is a
// power of 2 in both dimensions.
if (isPowerOf2(image.width) && isPowerOf2(image.height)) {
// Yes, it's a power of 2. Generate mips.
gl.generateMipmap(gl.TEXTURE_2D);
} else {
// No, it's not a power of 2. Turn of mips and set
// wrapping to clamp to edge
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
}
};
image.src = url;
return texture;
}