I work on a little project where i have to create plane with mouse detection.
For moment i just make some test on a cube from a simple exemple found on the web.
The detection is good and accurate but the container has to be scaled when mouse wheel in order to make zoom.
(i also have to make a zoom on some images, the purpose is to superimpose images with some 3D forms in order to create an accurate detection on my images, these images are scaled with css transform so i guess the simple way is to do the same with the canvas container)
The problem come after scalling this canvas container (using css transform), the raycasting doesnt remain exact and i dont really know how to fix it, i tried to change some value but in a random way.
I guess there is something to do with the scale factor applied on the container but i dont understand which variable i have to modify.
I will try to scale the canvas using three.js directly and following the scale that i apply on my images but i dont know if that would be easier.
Here is my test : http://pixelreseller.com/src_pixelreseller/projets/three-test/
You can see code by the code source but if you prefer that i copy/paste code here, let me know.
Related
i'm a beginner in Javascript so please bear with me.
Basically I'm making a sandbox drawing facility for a website using Javascript. And this is done using the canvas. What I need to do is to be able to resize the canvas dynamically but at the same time keep everything on the canvas to scale.
I don't think this question has been asked before. It seems trivial but I currently have all my objects on the canvas defined in absolute coordinates. I also have mouse events to use to draw things. And when I want to enlarge the canvas (by doubling the size say). All the objects inside won't be enlarged properly to scale and the mouse coordinate system would be messed up too.
Only solution i can think of is add a scale factor to ALL my drawing parts, but this is very tricky with a lot of code. Is there a better way?
If you don't mind jaggies on your double-sized canvas drawings then you can simply use CSS to double-size your canvas. Then divide every incoming mouseEvent coordinate by 2.
If you don't want jaggies on your double-sized canvas then:
Double-size the canvas element: canvas.width*=2 and canvas.height*=2 This automatically erases all canvas content.
Scale up the canvas: context.scale(2,2)
Redraw all your drawing parts using the unchanged original coordinates. A happy note: you do not have to scale any of your drawing coordinates -- context.scale automatically does that for you.
Divide every incoming mouseEvent coordinate by 2.
I'm trying to figure out if it is possible to stretch in image in Javascript so different parts of the image expand more quickly than others. I was thinking along the lines of an black/white map where black does not stretch at all, white stretches the most and the shades of grey in between stretch proportionately. Is this at all possible? I;m hoping to make a picture look as if its losing or gaining weight.
Thanks!
You could use the HTML5 canvas feature along Java-script to do image manipulation.
Altogh it will be processor intensive, mainly if you want to do animation, you can do it.
Some tutorial for the canvas element of HTML5 with Java-script, probably you are interested more on the drawImage(image,x,y) method.
http://www.w3schools.com/html/html5_canvas.asp
And references
http://www.w3schools.com/tags/ref_canvas.asp
You could then get draw the parts you want scaled, but giving it near non noticeable artifacts effects like you want is really difficult.
I am trying to transform a non-uniformed portion of image in a canvas element to a proper rectangle (ie. Like taking a non-rectangle portion of an image in photoshop and using Distort to make it rectangle), but am having difficulty understanding Canvas Matrix Transforms.
I am not after code, just a point in the right direction, in terms of understanding how I could achieve this.
Cheers
Update 1: Incase I didn't explain well enough http://i.imgur.com/QTB6q.png
Update 2: The those boxes are an area inside a photo which was added to the canvas, essentially I am cropping and straightening a portion of the image.
In html5 canvas you can apply only affine transformations using transform or setTransform() methods, so you need to know what is the matrix applied already and using the inverse matrix to make it look like a square area, for other transformations (non-affine), it is needed some math knowledge (that I don't have), create or search for an implementation for Canvas API (which works only with affine transformations).
I would like to have a repeated pattern of squares (a little like a blueprint) as a background to the entire SVG element. I am using Raphael. How can I accomplish this?
I want to do this with SVG rather than images as I pan / zoom the SVG using SetViewBox and I would like the background to scale appropriately too.
One option is to render those squares the usual way, via paper.rect(). Might be expensive, though, and would take some maintenance if the canvas can grow in size.
The other option is to do a patterned fill, paper.rect(0,0,100,100).attr({fill: "url(images/pattern.png)"}); (see this tutorial), which should automatically repeat the image it is given. I haven't done that myself, though, so I'm not really sure how the pattern is scaled when you do SetViewBox().
http://raphaeljs.com/polar-clock.html
I'd like to create this without using SVC or Canvas. Can anyone point me in the direction of examples doing something similar with css?
Thanks!
Well, SVG certainly seems to be the correct solution to this (or canvas, but I would prefer SVG). And the Raphael script will even work in old versions of IE as it switches to VML in IE6/7/8, so if you're trying to avoid SVG/Canvas because of that then you don't need to worry.
But you're asking how to do it without them, so I'll see what I can do...
There are a number of people who have demonstrated drawing some quite complex shapes using pure CSS. See http://css-tricks.com/examples/ShapesOfCSS/ for example.
With pure CSS/HTML, the only realistic way to draw curves is using the border-radius style. A circle as per the example in the question could be achieved using a square element with border-radius, and a thick border.
Drawing concentric circles as per the question would involve numerous elements layered on top of each other, each styled similarly, but at different sizes.
Now the tricky bit. To turn them from circles into arcs is going to be harder. The only sensible way I can think of to do it would be to layer some more elements on top of the circles coloured the same as the background, to obscure part of the circle. We would need to use CSS transform to rotate them so that the angle of the cut-off was correct.
So it could be done.
Animating it (certainly as nicely as in the example) would be another order of magnitude more difficult, and I wouldn't want to even start thinking about it. Just give me the SVN any day.