It looks to me like labels are meant to be anchored to objects in the map. In this case, I want to display some text on top of the map all of time.
I want it to be in the webgl itself, not an html element on top of it.
There are probably a million different ways to better accomplish your REAL objective, if you'd only state what that is, but anyway, if you're really determined to do what your question states...
Make an image with your text.
Base64 Encode that image.
Initialize the map with preserveDrawingBuffer: true (note, performance will suffer)
Use the following code. Replace the long base64 string with YOUR image. Replace the token with YOUR token.
// TO MAKE THE MAP APPEAR YOU MUST
// ADD YOUR ACCESS TOKEN FROM
// https://account.mapbox.com
mapboxgl.accessToken = 'REPLACEME';
const map = new mapboxgl.Map({
container: 'map', // container ID
// Choose from Mapbox's core styles, or make your own style with Mapbox Studio
style: 'mapbox://styles/mapbox/streets-v11', // style URL
center: [-74.5, 40], // starting position [lng, lat]
zoom: 9, // starting zoom
projection: 'globe', // display the map as a 3D globe,
preserveDrawingBuffer: true
});
map.on('render', () => {
var img, tex, vloc, tloc, vertexBuff, texBuff;
var cvs3d = map.getCanvas();
var ctx3d = cvs3d.getContext("experimental-webgl");
var uLoc;
ctx3d.pixelStorei(ctx3d.UNPACK_FLIP_Y_WEBGL, true);
// create shaders
var vertexShaderSrc = `
attribute vec2 aVertex;
attribute vec2 aUV;
varying vec2 vTex;
uniform vec2 pos;
void main(void) {
gl_Position = vec4(aVertex + pos, 0.0, 1.0);
vTex = aUV;
}`;
var fragmentShaderSrc = `
precision highp float;
varying vec2 vTex;
uniform sampler2D sampler0;
void main(void){
gl_FragColor = texture2D(sampler0, vTex);
}`;
var vertShaderObj = ctx3d.createShader(ctx3d.VERTEX_SHADER);
var fragShaderObj = ctx3d.createShader(ctx3d.FRAGMENT_SHADER);
ctx3d.shaderSource(vertShaderObj, vertexShaderSrc);
ctx3d.shaderSource(fragShaderObj, fragmentShaderSrc);
ctx3d.compileShader(vertShaderObj);
ctx3d.compileShader(fragShaderObj);
var progObj = ctx3d.createProgram();
ctx3d.attachShader(progObj, vertShaderObj);
ctx3d.attachShader(progObj, fragShaderObj);
ctx3d.linkProgram(progObj);
ctx3d.useProgram(progObj);
ctx3d.viewport(0, 0, 64, 64);
vertexBuff = ctx3d.createBuffer();
ctx3d.bindBuffer(ctx3d.ARRAY_BUFFER, vertexBuff);
ctx3d.bufferData(ctx3d.ARRAY_BUFFER, new Float32Array([-1, 1, -1, -1, 1, -1, 1, 1]), ctx3d.STATIC_DRAW);
texBuff = ctx3d.createBuffer();
ctx3d.bindBuffer(ctx3d.ARRAY_BUFFER, texBuff);
ctx3d.bufferData(ctx3d.ARRAY_BUFFER, new Float32Array([0, 1, 0, 0, 1, 0, 1, 1]), ctx3d.STATIC_DRAW);
vloc = ctx3d.getAttribLocation(progObj, 'aVertex');
tloc = ctx3d.getAttribLocation(progObj, 'aUV');
uLoc = ctx3d.getUniformLocation(progObj, 'pos');
var drawImage = function(imgobj, x, y, w, h) {
tex = ctx3d.createTexture();
ctx3d.bindTexture(ctx3d.TEXTURE_2D, tex);
ctx3d.texParameteri(ctx3d.TEXTURE_2D, ctx3d.TEXTURE_MIN_FILTER, ctx3d.NEAREST);
ctx3d.texParameteri(ctx3d.TEXTURE_2D, ctx3d.TEXTURE_MAG_FILTER, ctx3d.NEAREST);
ctx3d.texImage2D(ctx3d.TEXTURE_2D, 0, ctx3d.RGBA, ctx3d.RGBA, ctx3d.UNSIGNED_BYTE, imgobj);
ctx3d.enableVertexAttribArray(vloc);
ctx3d.bindBuffer(ctx3d.ARRAY_BUFFER, vertexBuff);
ctx3d.vertexAttribPointer(vloc, 2, ctx3d.FLOAT, false, 0, 0);
ctx3d.enableVertexAttribArray(tloc);
ctx3d.bindBuffer(ctx3d.ARRAY_BUFFER, texBuff);
ctx3d.bindTexture(ctx3d.TEXTURE_2D, tex);
ctx3d.vertexAttribPointer(tloc, 2, ctx3d.FLOAT, false, 0, 0);
ctx3d.drawArrays(ctx3d.TRIANGLE_FAN, 0, 4);
};
img = new Image();
img.src = 'data:image/png;base64,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';
img.onload = function() {
drawImage(this, 0, 0, 64, 64);
var img2 = new Image();
img2.src = 'data:image/png;base64,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';
img2.onload = function() {
drawImage(img2, 64-16, 64-16, 16, 16); // draw in bottom right corner
}
};
});
Fiddle (you have to change map token in order to see it in action): https://jsfiddle.net/rygj51ca/1/
The above code will render an image of a smiley on the mapbox canvas, bottom left corner, every time the map renders.
If you want text in "the top right corner", then you don't want it in the map at all, you want it over the map.
In that case, the best way is just to use a different HTML element, styled however you like. Along these lines:
<div id="map" />
<div id="text-overlay" style="position: absolute; right: 0; top: 0;>Here's my text</div>
Related
This question already has an answer here:
Fragment Shader: wrong color value from texture
(1 answer)
Closed 6 months ago.
I am trying to load a texture into WebGl and read a pixel color from it (to eventually use in a shader). When I read the pixel color at position 70,70 in python, I get (255,0,0,255) which is what I expected. But when I read it in WebGL, I get (255,38,0,255). What am I missing here?
Image: https://i.imgur.com/jGA12NE.png
JSFiddle: https://jsfiddle.net/6u7h0sj1/3/
Python code:
import requests
from io import BytesIO
response = requests.get('https://i.imgur.com/jGA12NE.png')
im = Image.open(BytesIO(response.content))
pixels=im.load()
print(pixels[70,70])
Javascript code to read pixel of texture:
const canvas = document.createElement('canvas');
document.body.appendChild(canvas);
const gl= canvas.getContext("webgl",{"antialias":true});
function loadTexture(){
const texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
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.crossOrigin = ""; // or "anonymous", will be interpreted the same
image.onload = () => {
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, level, internalFormat,
srcFormat, srcType, image);
let width=1;
let height=1;
let x=70;
let y=70;
var fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
var pixels = new Uint8Array(width * height * 4);
gl.readPixels(x, y, width, height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
document.getElementById("test").textContent=pixels;
}
};
image.src = 'https://i.imgur.com/jGA12NE.png';
}
loadTexture();
Found this helpful answer:
Fragment Shader: wrong color value from texture
Solved by adding the following line before loading the texture:
gl.pixelStorei(gl.UNPACK_COLORSPACE_CONVERSION_WEBGL, false);
I wanted to show a vertical line that follows my mouse on my chartjs canvas and the following codes does what I one except one thing, it will stop updating once the tooltips fades out (when there is no data intersects with my cursor). I know it has something to do with rendering but I do not know how and what variable I have to manipulate with.
I can force the animation playing non-stop by setting my animation as timed loop but I don't think this is a proper solution. This will also consume more resources since I need only my lines to be updating constantly not the whole graph.
The function is implemented with inline plugin.
Please have a look, thank you!
let canvas = document.getElementById('myChart')
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect();
return {
x: evt.clientX - rect.left,
};
}
let mousePosX;
canvas.addEventListener('mousemove', function(evt) {
var mousePos = getMousePos(canvas, evt);
mousePosX = mousePos.x;
}, false);
const config = {
type: 'scatter',
plugins: [
{
afterDraw(chart) {
let x = mousePosX;
let yAxis = chart.scales.y;
let ctx = chart.ctx;
ctx.save();
ctx.beginPath();
ctx.moveTo(x, yAxis.top);
ctx.lineTo(x, yAxis.bottom);
ctx.lineWidth = 1;
ctx.strokeStyle = 'rgba(0, 0, 255, 0.4)';
ctx.stroke();
ctx.restore();
},
}
],
.....
I am moving some code from Leaflet into Mapbox GL JS. I have a 2d animated canvas which is rendered correctly when viewed top-down (pitch 0), rotated (bearing whatever), but is skewed when the pitch isn't zero. I have spent the past few days trying to correct it without much success.
My code needs to be able to convert between screen dimensions and map coordinates. E.g. for a given pixel, what lat-lon results (with map.project([lon, lat]) ). Or for a lat-lon, what pixel does it correspond to (with map.unproject([x,y]) ). When the canvas is rendered with pitch 0, the latitudes are equally spaced (*enough) across the pixels and everything works as desired. The conversions occur correctly.
When pitch is > 0, the coordinate conversions appear to work as expected as well. However, I think Mapbox GL JS takes the canvas, and turns it into a WebGL texture. This texture is then somehow scaled/rotated which turns the previous rectangle canvas into a trapezoid.
I need to be able to include this trapezoid scaling or account for this distortion in the canvas calculations.
Rough Sample
The snippet below is an attempt at replicating what is going on with a far simpler codebase. It's based on https://docs.mapbox.com/mapbox-gl-js/example/canvas-source/. You'll see the circles moving around, turning into ovals at different points and stretching--they should remain circles. This is partly caused by the map.unproject() calls using the screen dimensions, which are used to determine the map bounds. In 2d space, this works well because the screen bounds are identical to the camera view. But I think in 3d space, the screen dimensions are distorted by the camera view, and so the relation is lost between screen--camera--map which causes the skew.
My goal is to either correct the skew, or somehow use the camera properties to create the bounds (and project/unproject), OR there's another way to solve this. Essentially I want what is on the canvas at particular coordinates to stay there and not moved when pitched.
Thank you!
const PITCH = 45; // Change to 0 to see uniform shapes
// Based on https://docs.mapbox.com/mapbox-gl-js/example/canvas-source/
mapboxgl.accessToken = 'pk.eyJ1IjoiYnVzaGZpcmVpbyIsImEiOiJjazU3NGwzNGEwM2QxM2VwcWJ0djk1amFyIn0.DP3giqn33iswMWzlclr9jg';
var map = new mapboxgl.Map({
container: 'map',
zoom: 5,
minZoom: 4,
center: [95.899147, 18.088694],
pitch: PITCH,
style: 'mapbox://styles/mapbox/streets-v11'
});
//Animation from https://javascript.tutorials24x7.com/blog/how-to-draw-animated-circles-in-html5-canvas
var canvas = document.getElementById('canvasID');
var ctx = canvas.getContext('2d');
var circles = [];
var radius = 20;
function Circle(x, y, dx, dy, radius, color) {
this.x = x;
this.y = y;
this.dx = dx;
this.dy = dy;
this.radius = radius;
this.draw = function () {
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
ctx.strokeStyle = color;
ctx.stroke();
};
this.update = function () {
if (this.x + this.radius > 400 || this.x - this.radius < 0) {
this.dx = -this.dx;
}
if (this.y + this.radius > 400 || this.y - this.radius < 0) {
this.dy = -this.dy;
}
this.x += this.dx;
this.y += this.dy;
this.draw();
};
}
for (var i = 0; i < 5; i++) {
var color =
'#' +
(0x1000000 + Math.random() * 0xffffff).toString(16).substr(1, 6);
var x = Math.random() * (400 - radius * 2) + radius;
var y = Math.random() * (400 - radius * 2) + radius;
var dx = (Math.random() - 0.5) * 2;
var dy = (Math.random() - 0.5) * 2;
circles.push(new Circle(x, y, dx, dy, radius, color));
}
function animate() {
requestAnimationFrame(animate);
ctx.clearRect(0, 0, 400, 400);
for (var r = 0; r < 5; r++) {
circles[r].update();
}
}
animate();
let size = this.map.getContainer();
const nw = map.unproject([0, 0]);
const ne = map.unproject([size.clientWidth, 0]);
const se = map.unproject([size.clientWidth, size.clientHeight]);
const sw = map.unproject([0, size.clientHeight]);
map.on('load', function () {
map.addSource('canvas-source', {
type: 'canvas',
canvas: 'canvasID',
coordinates: [
[nw.lng, nw.lat],
[ne.lng, ne.lat],
[se.lng, se.lat],
[sw.lng, sw.lat],
],
animate: true
});
map.addLayer({
id: 'canvas-layer',
type: 'raster',
source: 'canvas-source'
});
});
body { margin: 0; padding: 0; }
#map { position: absolute; top: 0; bottom: 0; width: 100%; }
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Canvas Demo</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<link href="https://api.mapbox.com/mapbox-gl-js/v2.3.1/mapbox-gl.css" rel="stylesheet">
<script src="https://api.mapbox.com/mapbox-gl-js/v2.3.1/mapbox-gl.js"></script>
</head>
<body>
<canvas id="canvasID" width="400" height="400">Canvas not supported</canvas>
<div id="map"></div>
</body>
</html>
I am trying to visualise a three.js scene in Mapbox, using an approach based on this tutorial: https://docs.mapbox.com/mapbox-gl-js/example/add-3d-model/
I have a prepared scene named "threescene", which I added to the scene of the custom layer. It contains geometries of buildings. The coordinates are in WGS84, and it seems like they would be transformed properly in the tutorial code.
However, the layer simply does not show up. I don't know if I should do something else with the coordinates, or if there is another problem. I have already attempted to normalise the coordinates within the scene.
My code is as follows:
mapboxgl.accessToken = 'pk.eyJ1IjoiamxpZW1wdCIsImEiOiJjanpzZHNhOGwxZ3RjM2JuenBpcjN4eTh3In0.dnO_1v0NDfRMZBhv-hVvjQ';
var map = window.map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/light-v10',
zoom: 18,
center: [6.8309373573, 53.0475174735], // min of bbox
pitch: 60,
antialias: true // create the gl context with MSAA antialiasing, so custom layers are antialiased
});
// parameters to ensure the model is georeferenced correctly on the map
var modelOrigin = [6.8309373573, 53.0475174735]; // min of bbox
var modelAltitude = 0;
var modelRotate = [Math.PI / 2, 0, 0];
var modelAsMercatorCoordinate = mapboxgl.MercatorCoordinate.fromLngLat(modelOrigin, modelAltitude);
// transformation parameters to position, rotate and scale the 3D model onto the map
var modelTransform = {
translateX: modelAsMercatorCoordinate.x,
translateY: modelAsMercatorCoordinate.y,
translateZ: modelAsMercatorCoordinate.z,
rotateX: modelRotate[0],
rotateY: modelRotate[1],
rotateZ: modelRotate[2],
/* Since our 3D model is in real world meters, a scale transform needs to be
* applied since the CustomLayerInterface expects units in MercatorCoordinates.
*/
scale: modelAsMercatorCoordinate.meterInMercatorCoordinateUnits()
};
var THREE = window.THREE;
// configuration of the custom layer for a 3D model per the CustomLayerInterface
var customLayer = {
id: '3d-model',
type: 'custom',
renderingMode: '3d',
onAdd: function(map, gl) {
this.camera = new THREE.Camera();
this.scene = new THREE.Scene();
this.scene.add(threescene); // here I include my scene
// create two three.js lights to illuminate the model
var directionalLight = new THREE.DirectionalLight(0xffffff);
directionalLight.position.set(0, -70, 100).normalize();
this.scene.add(directionalLight);
var directionalLight2 = new THREE.DirectionalLight(0xffffff);
directionalLight2.position.set(0, 70, 100).normalize();
this.scene.add(directionalLight2);
this.map = map;
// use the Mapbox GL JS map canvas for three.js
this.renderer = new THREE.WebGLRenderer({
canvas: map.getCanvas(),
context: gl,
antialias: true
});
this.renderer.autoClear = false;
},
render: function(gl, matrix) {
var rotationX = new THREE.Matrix4().makeRotationAxis(new THREE.Vector3(1, 0, 0), modelTransform.rotateX);
var rotationY = new THREE.Matrix4().makeRotationAxis(new THREE.Vector3(0, 1, 0), modelTransform.rotateY);
var rotationZ = new THREE.Matrix4().makeRotationAxis(new THREE.Vector3(0, 0, 1), modelTransform.rotateZ);
var m = new THREE.Matrix4().fromArray(matrix);
var l = new THREE.Matrix4().makeTranslation(modelTransform.translateX, modelTransform.translateY, modelTransform.translateZ)
.scale(new THREE.Vector3(modelTransform.scale, -modelTransform.scale, modelTransform.scale))
.multiply(rotationX)
.multiply(rotationY)
.multiply(rotationZ);
this.camera.projectionMatrix.elements = matrix;
this.camera.projectionMatrix = m.multiply(l);
this.renderer.state.reset();
this.renderer.render(this.scene, this.camera);
this.map.triggerRepaint();
}
};
map.on('style.load', function() {
map.addLayer(customLayer, 'waterway-label');
});
You say your coordinates are in WGS84 so you're saying your model is in WGS84, which has units of degrees, yet later on in the code you've inherited the modelScale as in meters.
So which units is your model in, meters or degrees, and which coordinate reference system is it? As you'll need to apply the correct scale transform depending on this.
I want to render high precision float values to a texture, but the values I read are clamped to [0, 1]. Is there anyway to get unclamped values?
Here is the fragment portion of the shader code:
float4 frag (v2f i) : SV_TARGET
{
return float4(0.098, 0.698, 200, 100000); // Obviously a contrived example.
}
Here is the code creating the texture to render to:
RenderTextureDescriptor rtd = new RenderTextureDescriptor(1, 1, RenderTextureFormat.ARGBFloat);
RenderTexture rt = RenderTexture.GetTemporary(rtd);
RenderTexture.active = rt;
mainCamera.SetReplacementShader(selectionShader, "");
mainCamera.Render(); // OnPostRender will be called
mainCamera.ResetReplacementShader();
Read code (in OnPostRender):
Texture2D hitTexture = new Texture2D(1, 1, TextureFormat.RGBAFloat, false);
Rect rect = new Rect(0, 0, 1, 1);
hitTexture.ReadPixels(rect, 0, 0, false);
Color pixelSample = hitTexture.GetPixel(0, 0);
Debug.Log("Sample: " + pixelSample);
The output is "RGBA(0.098, 0.698, 1.000, 1.000)", rather than "RGBA(0.098, 0.698, 200, 100000)" as hoped/expected.