For a 2d grey image, I want to extract each pixel's grey/brightness value as depth/z-index to generate a smooth 3d plane, something like a brightness level depth map.
My simple idea is that loop add each pixel as a point in the scene, and set z-index with grey value.
But, first how to add points(a very small one to represent a pixel) with Three.js?
And, is this a good way? is this a smooth plane? what if a large image(e.g. 2000*4800, I don't think memory can hold that much points)?
Related
Currently I have an image that needs to be manipulated so it matches the same scale, position, and rotation as a template.
The grey rectangle with a circle in the middle is the template.
The orange rectangle and circle represents the user's input. It needs to be rotated, scaled and aligned to it matches the grey one. I'm currently stumped on how to proceed. I've no code other than the following.
function align_image()
{
// clever transform alignment code here
}
Bad dog, no biscuit!
The process at of aligning the images would normally be done manual input and judged by eye. I'm hoping to automate this step and align the image to its respective size and position but leaving the comfort and safety of Photoshop DOM I'm not sure how to proceed or even if this is a trivial matter or one left best alone. The project is web based currently using javascript and three.js
So if anyone can give me some pointers I'd appreciated it.
I don't code javascript so I can only talk about the algorithm. Generally best tool for registration is to use feature matching methods (using sift, surf,...) but your image is not the kind that have strong features. Now if you're always dealing with rectangles and circles in your images, find the "edges" of the rectangle with Hough Transform, compute the angle of those edges (lines) then rotate the image with that angle in the opposite direction.
Then with the help of Hough Circle Detector, find the center of the circles in the middle of the images, calculate the distance between them, and move the target rectangle to the source's circle position. After the movement by comparing the radius of the circles, you can resize the target image to make it like the source rectangle.
All of these are conveniently doable with Opencv.
I'm creating a 2d game in HTML5 canvas. It's an isometric world, so actually it's also 3d.
You always see that isometric games use tiles, and I think the reason is just for the depth logic.
My goal is to create the game without using a tile system. Each item can be placed by the user, so item locations like walls, trees, etc., have variable positions. The positions are isometric x, y, z coordinates.
If the game was just tiled, you could determine a fixed tile area for each item. (I mean: a one-tile item, or a wall of 10 tiles long).
But in my game I use an areaX and areaY for the space an item uses on the ground. And I use a height to store an item's height, which is the z value. (z axiz in my world, is y axis on screen).
The problem is hard to explain. It's about depth sorting.
See the following image:
The brown bar on top of the other bar should be after the gray pole.
I'm now using the simplest form of a painter's algorithm, that only compares the x, y, z coords of each item.
I know this incorrect rendering is a famous problem of the painter's algorithm.
If this was a tiled game, the bars could be divided into 2 tiles next to each other. Then the tiles could be drawn in the order of their depth.
But since I'm trying to create it without tiles, I am looking for a really challenging logic.
The items should be rendered as if they were 3D objects. I would even like to have the following behavior: If multiple items would intersect, then the visible pixels of each item should be drawn, like in this image:
The main problem is that there is no information to determine what parts of an image should be visible, and how they must be cut.
I could create a depth mask for each image, like:
It works a little bit like a z-buffer.
But this is not possible due to the performance of a canvas, because you have to iterate literally over each pixel of each image in the map.
And the second big disadvantage is that you have to load twice as much resources from the server...
Another solution might be cutting all images into vertical strips of 1 pixel wide. Then handle each strip as if it's a tile of 1x1 pixel. Then I'm still creating a tiled game, buy the tiles would be so small that I still reach my goal. But also this solution has the disadvantage performance... Since each image would be split in hundreds of strips, which are new seperate images.
So I'm looking for a challenging solution. Who can help me finding a way to define the depths (or depth areas) for images in a way that correct rendering is possible for the performance of canvas?
This question was effectively asked again and answered over here
The short answer is you can use depth sprites with WebGL
I'm working on writing a software 3d engine in Javascript, rendering to 2d canvas. I'm totally stuck on an issue related to the projection from 3d world to 2d screen coordinates.
So far, I have:
A camera Projection and View matrix.
Transformed Model vertices (v x ModelViewProj).
Take the result and divide both the x and y by the z (perspective) coordinate, making viewport coords.
Scale the resultant 2d vector by the viewport size.
I'm drawing a plane, and everything works when all 4 vertices (2 tris) are on screen. When I fly my camera over the plane, at some point, the off screen vertices transform to the top of the screen. That point seems to coincide with when the perspective coordinate goes above 1. I have an example of what i mean here - press forward to see it flip:
http://davidgoemans.com/phaser3d/
Code isn't minified, so web dev tools can inspect easily, but i've also put the source here:
https://github.com/dgoemans/phaser3dtest/tree/fixcanvas
Thanks in advance!
note: I'm using phaser, not really to do anything at the moment, but my plan is to mix 2d and 3d. It shouldn't have any effect on the 3d math.
When projection points which lie behind of the virtual camera, the results will be projected in front of it, mirrored. x/z is just the same as -x/-z.
In rendering pipelines, this problem is addresses by clipping algorithms which intersect the primitives by clipping planes. In your case, a single clipping plane which lies somewhere in front of your camera, is enough (in rendering pipelines, one is usually using 6 clipping planes to describe a complete viewing volume). You must prevent the situation that a single primitive has at least one point on front of the camera, and at least another one behind it (and you must discard primitives which lie completely behind, but that is rather trivial). Clipping must be done before the perspective divide, which is also the reason why the space the projection matrix transforms to is called the clip space.
I am attempting to use an html canvas element to draw each character available in a font file to a canvas. To make this question as simple as possible, pretend only one character is drawn to a canvas. From there, I want to use Javascript to analyze the canvas and create triangle regions of the canvas that make up the entire character. The reason I need it in triangles is so that the data can later be sent to WebGL so text can be rendered and data will not be lost be scaling the text size up or down.
I am looking for some sort of algorithm to accomplish this or at least some knowledge to get me going in the right direction. If you believe I should use a different approach please tell me why, but I figured this would be the best to provide a way to modify text in many ways as well as make it possible to create 3d block text.
Here's an article on how to draw resolution independent curves with shaders
http://research.microsoft.com/en-us/um/people/cloop/loopblinn05.pdf
My understanding is instead of breaking the shapes into triangles you break them into quads with enough info sorted in the vertices to draw a portion of the curve inside each quad. In other words, as the shader draws each quad there's a formula that for each pixel can compute if that pixel is inside the curve or outside the curve.
I suggest you to start with the keyword Polygon Triangulation.
Using this methods, you can split n-Polygons into triangles like this:
These methods may only apply to figures with real (and not rounded) edges.
So, you are trying to convert a raster image into vector data?
When zoomed in, that will result in very jagged looking geometry.
Since each pixel is being treated as a square edged part of the geometry.
Couldn't you get your hands on the original vector (bezier curve) geometry for each glyph you are drawing?
Transforming that into triangle strips and fans would look smoother.
I've been working on a WebGL project that runs on top of the Three.js library. I am rendering several semi-transparent meshes, and I notice that depending on the angle you tilt the camera, a different object is on top.
To illustrate the problem, I made a quick demo using three semi-transparent cubes. When you rotate the image past perpendicular to the screen, the second half of the smallest cube "jumps" and is no longer visible. However, shouldn't it still be visible? I tried adjusting some of the blending equations, but that didn't seem to make a difference.
What I'm wondering is whether or not this is a bug in WebGL/Three, or something I can fix. Any insight would be much appreciated :)
Well, that's something they weren't able to solve when they invented all this hardware accelerated graphics business and sounds like we'll have to deal with this for a long while.
The issue here is that graphic cards do not sort the polygons, nor objects. The graphics card is "dumb", you tell it to draw an object and it will draw the pixels that represent it and also, in another non-visible "image" called zbuffer (or depthbuffer), will draw the pixels that represent the object but instead of color it will draw the distance to the camera for each pixels. Any other objects that you draw afterwards, the graphics card will check if the distance to the camera for each pixel, and if it's farther, it won't draw it (unless you disable the check, that is).
This speeds up things a lot and gives you nice intersections between solid objects. But it doesn't play well with transparency. Say that you have 2 transparent objects and you want A to be drawn behind B. You'll need to tell the graphics card to draw A first and then B. This works fine as long as they're not intersecting. In order to draw 2 transparent objects intersecting then the graphics would have to sort all the polygons, and as the graphics card doesn't do that, then you'll have to do it.
It's one of these things that you need to understand and specifically tweak for your case.
In three.js, if you set material.transparent = true we'll sort that object so it's drawn before (earlier) other objects that are in front. But we can't really help you if you want to intersect them.