As image shows there is all values we can set while making viewshed but heading angle is not working. see if somebody can help.
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I am in the midst of reimplementing an interactive heatmap from svg to canvas in javascript. I was wondering if anyone had any ideas for how allow someone to select an area and have it zoom into that area using html5 canvas and js.
Many thanks,
Tom
Disclaimer: Because you haven't provided any code I am going to stick to Strategy here :)
Method 1: DIY
First thing you will have to decide is what your resolution or cell size in your case is and what happens to a individual cell when you zoom.
Case 1: Your cell size increases, and you just multiply the cellsize by the factor of zoom and clip the area that goes out of bounds of what user selected.
Case 2: You want your heatmap cells to be pixel sized in which case when you zoom in, now each of the previous pixel(or cell) will have to interpolated and you will increase the resolution by the factor of zoom. Of course you will have to re-run heat map function for that region with a greater resolution.
Once you have one of the two strategy figured out, Implementation on JavaScript it actually quite simple.
You hook into drag-event. and let users draw a rectangle to show them the reference area they are zooming into.
Then you calculate you zoom factor based on the ratio of the drawn rectangle, to the original image or the container. This becomes your zoom-factor
Now using the zoom factor you generate a new image, based on Case1 or Case2 depending on which you go with
Finally you replace existing image with old one.
Viola! Zoom!!
Method 2: Use a Library!
Use a awesome library like OpenLayers 3, and just load your heatmap into it. Here's an Heatmap Example done in OpenLayers 3. Zoom pan now come for FREE!
Hope this helps.
I am trying to make an 'Eraser' for my fabricjs-based 0.5 Opacity free drawing app(with non-trivial background image), i. e. everything drawing is half-transparent and we still can see the background through the free drawing.
However I understand by default all free drawing are 'path-based' i. e. everything we draw (between mouse-down mouse up) is captured as an individual path in the canvas, so it is not possible to erase arbitrary part of the path. So I am thinking maybe we can capture the mouse-down/up event manually and draw an image pixie by pixie and place it on the canvas with opacity=0.5? so that we can use white to overwrite all those 'old' drawing?
Is this a workable/efficient enough solution?
However I am not sure how this can be implemented in fabricjs? could you please give me some advise on the steps or some pseudocode? thanks
I didn't complete my attempt when i had a similar problem , but the basic concept was simple 'Read the pixel under the cursor(and under the canvas, where another canvas with a background image was) and paint the path with the same color' , creating an eraser effect. The starting stone was this jsfiddle.net/DV9Bw/1/ maybe it can help you out, i didn't try it to its completion since the idea was quickly abandoned
i want to create a animation in WebGl, my idea is like this:
You inside a large rectangle.
The sides of this rectangle are animated with image of a binary gif.
The camera is going forward until infinity.
I want to create like this image in WebGl:
http://i.stack.imgur.com/D0GpT.jpg
But i don't know, how do put the camera inside a large rectangle and going the camera to forward until infinity, someone can help me?
Here's what the author called "nano-Doom" :-) It has a few planes which make up a world, and you can move the camera around with the keyboard:
http://learningwebgl.com/blog/?p=1067
Given the little information you provided in your question, my suggestion would be to run through the preceeding lessons up to the one given above.
For a game we develop with libgdx, we need to show the user the remaining time for making a move.
How can we render a circular progress bar which shows the remaining seconds?
In the following answer there is a javascript solution :
Circular / radial progress bar
Thanks.
First create a texture (region) with the full circular progress bar. Next deform a shape (mesh) made up of one or more triangles to fit the actual area which should be shown.
For this, think of a line from the center of the image to the bounds of the image. Calculate the intersection point (and "wall", i.e. left, right, top or bottom of the image) of the line at the given angle. This will give you the portion of the texture (region) that needs to be drawn.
For example, if the line at rest (angle is zero) crosses the bottom wall of the image at the middle, your image is square and you want to rotate clockwise, then everything between 45 and 135 degrees hits the left wall, between 135 and 225 degrees hits the top wall, and so on.
Now you have the shape, you'll need to express it in triangle. Or to maintain compatibility with libgdx's spritebatch, an even number of triangles. Make sure to update the U and V values according to the location of the vertex.
A simple implementation of this can be found over here: https://github.com/xoppa/world/blob/master/src/com/xoppa/android/misc/RadialSprite.java
You could use an OpenGL shader to generate a circular progress bar. Here is an animated timer that would be a good place to start: http://glsl.heroku.com/e#10201.0
However, I don't think there is any good Libgdx infrastructure for dropping in shaders like this. You would have to use the OpenGL APIs (see https://code.google.com/p/libgdx/wiki/OpenGLShader).
In my web application I want the user to be able to draw some rectangles on an image, also change the size of the rectangles and drag and drop them. after that I have to get coordinates of rectangles and send them to server's database
Is it better to create a canvas on a photo or load the image in canvas ?
I don't write any code yet because I have no idea how to do this.
Any ideas,suggestions,links,libraries ?
As the comment said canvas is a good bet for this, but you'd need to do a fair bit of coding to get it working.
I actually have a tutorial on making Canvas interactive by drawing rectangles and moving them around. It should give you a good start on this project.
There are also a few libraries, such as fabricJS, but that might be hard to get the coordinates out of without digging into the library.