I'm trying to animate a simple rectangular shape so that it scales in size in a certain direction. As it is, I am making a rectangle that extends from point A to B. The end goal is to animate it so that it starts at A and is transformed to be the length required to get to B.
I'm pretty new to animation in general, so this process seems finicky to me.
Right now I am:
Creating a vector between the start and end point
Finding the 8 corners of the rectangle along that vector
Creating 2 triangles for each face of the rectangle
Rendering the shape
This is all being done by using a MeshBuilder object and adding the triangles and points individually.
So, the way I'm creating the prism doesn't really help for what I need to do. Ideally I suppose, I would just create a short prism aligned between the points, and then just extend the rectangle to be the right length in an animation.
Any thoughts?
I solved this is a sense by scaling the 3D object from a size of 0 in the X/Y/Z to 1.0. So instead of the prism "extending" from A to B, it more or less "grows" to B.
Note that the ScaleTransform3D needed to have the CenterXYZ properties set to the coordinates of point A in order for it to be anchored to the correct position.
If I find a better solution, I'll update this answer later.
Related
I am trying to implement some kind of snapping functionality in WPF for a circle (which represents my mouse) and it should snap to another object (normally this would be a line or a rectangle).
Is there a way to do this kind of functionality with WPF without doing all the calculations on my own and if not is there an easy way (library?) to get this kind of information?
Edit: I want to snap the border of the circle to the border of the rectangle/line.
As a first step, you should find the point on the rectangle that is the closest to the cursor, and the distance between the two: extending the edges of the rectangle, you partition the plane into 9 regions. Depending on the region where the cursor lies, the searched distance will be the distance to a corner (Euclidean distance formula) or the distance to an edge (difference of abscissas or ordinates).
Subtract the circle radius from this distance. This will tell you if you are close enough for a snap.
When a snap is possible, move the cursor along the line from the current cursor position to the closest point until you hit the corner or edge. You will need to use the parametric equation of the line segment.
The complete discussion requires some care but only involves simple math.
A similar approach is possible to snap to a line segment. Here is a trick: if you rotate the line segment to make it horizontal, you can consider the line segment as a degenerate rectangle and use the same snapping algorithm. Rotate the line segment and the cursor, apply the snapping logics and then counter-rotate the updated cursor.
That kind of functionality only takes a few lines of code to replicate... I doubt that you'll find a 'library' of code to do it for you. The method is as follows:
Keep a collection that contains the 4 Points that form each shape's bounding box. You then need to handle to MouseMove event on the Canvas, or shape container. In this event, you simply need to ascertain whether the current mouse position is within a certain distance from any of the shape edges... you'll have a little bit more work to do with non-rectangular shapes to calculate their edges, but the principal is the same.
If you detect the presence of a nearby shape, then you simply need to change the value of the nearest dimension to that of the nearby shape... the snap. That's it... much easier than you think.
Ok, in my XNA project i've added simple shader + model loading code, anything works. I created a very simple low-detailed model in 3Ds Max. Exported and imported to XNA with FBX format.
The problem is:
if i move my simple camera to some distance from this model, one of its components starts to flicker. I tried another model and there is the same situation, some of components start to flicker and only if i get to some distance from model.
This flickering (or blinking or ..) appears only with textured objects (probably), and looks like:
in each frame random parts/pixels of model (or not so random) replaced with object which is behind a model or its component... :(
UPDATE: Now i know - problem is in my model (i checked some other models). I dont understand why but Plane object gives that flickering. Maybe the problem is not in Plane object.
This is only an educated guess but: Your far-plane is too far away, or your near-plane is too close, or both.
A perspective camera gives you a viewable area that looks like this:
Your Z-buffer (depth buffer) covers the range between the near and the far planes. A typical Z-buffer might have 24-bits of precision, giving you 224 possible values. The further apart your near and far planes are, the greater the world-space distance each possible value must covers. In other words: your Z buffer is less accurate.
What you are seeing is known as "Z-fighting". This is where the Z-buffer is not accurate enough to differentiate between the depths of two given pixels. So you end up with pixels that should have been rejected as being "behind" what was already rendered, drawn instead.
(Alternately your model has some coplanar or nearly coplanar triangles - that is triangles who's surfaces are too close together. Same issue: Not enough precision in the Z-buffer to differentiate between the two surfaces.)
You may also wish to enable backface-culling (RasterizerState.CullCounterClockwise), if it is not already enabled. This culls triangles facing away from the camera, removing one possible source of Z-fighting.
I have seen this happen before on models where there are two or more surfaces overlapping in the same plane, one surface is inside the other but in the same plane - so the system can not tell which surface is in front of the other and usually ends up with a mash-up of both surfaces.
It looks like you have a smaller rectangular surface intersecting with a larger rectangular surface that makes up the lower base shape of your model. Probably from another object inside the box? Or from a object subtraction error that left two rectangles inside each other on that surface maybe?
Either way modify the model so there are no longer two surfaces with in each other.
So I am working on a Risk type game in XNA/C#. I have a map, similar this one, and I need to be able to detect mouseovers on each territory (number). If these areas were squares, it would be easy, as they could each be represented by a rectangle. However, they are different size polygons. Is there a polygon shape that behaves similar to a square? If there isn't, how would I go about doing this?
I sugest this:attach color to each number, recreate your picture in these colors: every shape will be in its particular color. Dont draw it onscreen, use it only as reference map. And when the user clicks or moves mouse over your original map, you just simply project mouse coordinates into the color map, check the color of pixel laying under the mouse and because you have each color associated to number of territory...
This is not c# specific (as I've never written anything in the language, so no idea of what apis there are), though there are 2 algorithms that come to mind for detecting if a point is inside a polygon (which can be used to detect if a mouse point is over another polygon/map shape).
One is based on raycasting, where you cast a ray in 1 direction from the (mouse) point to "infinity" (edge of the board in this case) and count the number of times it crosses the polygon's edges. If it is odd, then the point is inside the polygon, if it is even, then the point is outside of the polygon.
A wiki link to it: http://en.wikipedia.org/wiki/Point_in_polygon#Ray_casting_algorithm
The other algorithm that comes to mind works only for triangles I think but it can be more simple to implement I think (taking a quick glance at your shapes, I think they can easily be broken down into triangles and some are already triangles). It is to do with checking if the point is on the same (internal) "side" of all the edges in the triangle. To find out what "side" a point is on vs an edge, you'd take create 2 vectors, the first vector would be the edge itself (made up of 2 points) and the other vector would be the first point of that edge to the input point, then calculate the cross product of those 2 vectors. The result will be negative or positive, which can be used to determine the "direction".
A link to it: http://www.blackpawn.com/texts/pointinpoly/default.html
(On that page is another algorithm that can also work for triangles)
Hit testing on a polygon is not so difficult to do in real time. You could use a KD-Tree for optimisation if the map is huge. Otherwise find a simple Contains method for a polygon and use that. I have one on another computer. Let me know if you'd like it.
I'd like to achieve an effect in XNA where I move a clipping plane through an object, and the object gradually disappears WHILE the clipped area is filled with a custom color or texture.
This is what I was able to achieve via HLSL:
And this is what I would actually need:
I think the teapot isn't a really great example because the models I would use would always be fully closed at all times.
Are there any good solutions to this?
I think that if you just have calculated if a pixel is front or back, you don´t need to clip it if the pixel is front, you only should set the pixel normal to the plane normal value, and calculate light as usual...
I am doing some sort of drawing software in WPF, and I have certain visual elements in a Canvas like for example Rectangles and Lines. I have implemented dragging of those elements around the Canvas to move them. The motion must be aligned to pixels, I read WPF uses points and not pixels so it has become a concern of mine to know whether my lines or rectangles are aligned to pixels. I tried using SnapsToPixels, but I'm not sure it will do the trick, or if it will do it when I'm moving the visuals around.
Finally, I must implement moving visuals with the keyboard, a single cursor stroke means move the visual exactly one pixel, how can I do this from the code behind? I assume doing something like:
Canvas.SetLeft(visual) = Canvas.GetLeft(visual) + 1;
Will only add one point to its position, and not one pixel, how can I move exactly one pixel in the Canvas?
Thank you very much.
It might help to use SnapToDevicePixels for your canvas.
Is this what you are looking for?
Matrix m =
PresentationSource.FromVisual(Application.Current.MainWindow)
.CompositionTarget.TransformToDevice;
double pixelSizeX = m.M11;
double pixelSizeY = m.M22;