I have a number of square regions in my game screen which, when actors move across these regions, I want the background image to show through from behind.
So, is it possible to draw to a SpriteBatch such that a region is subtracted/deleted from the texture (effectively "punching a hole" in it)?
I can't think how else to achieve this... Scissors seem incredibly impractical for my purpose, as I want to clip the areas INSIDE a number of squares. This is the inverse of Scissors - which clip areas OUTSIDE the scissors' bounds. The thought of calculating dozens of Scissor regions to fill the inverse areas between an assortment of square regions seems too impractical to be the solution... especially if the regions are moving.
Any help or suggestions appreciated!
UPDATE: Image attached.
I want the background to always be visible in the areas marked with the dotted lines. The dotted areas will move, so I'd rather not create more sprites from the background to lay on top, but rather have parts of the actors intersecting the dotted squares not be drawn. (Or any method that will achieve the same effect.)
I think the best hack is to not try and be so precise about clipping your actors, but to just re-draw the background on top the actors (and to clip that).
Specifically:
draw the whole background
draw your actors/sprites
draw the background with one cliprect for one part that "shows through"
draw the background with another cliprect for the other part that "shows through"
draw the dotted boxes around your cliprect areas
Great image, by the way. Easily worth 1000 words. :)
Related
I am drawing a coloured circle within an NSView that is contained in an NSMenuItem. When I do so, the circle is drawn in a darker colour to the one I specify and when I add a subview with no drawing code, the area occupied by that view is drawn in the true colour, as illustrated by the image. Could someone explain to me why this is happening and how to fix it?
Many Thanks, Ben.
When you use Graphics.drawTriangles() and Graphics.beginBitmapFill() to draw two triangles to create a rectangle face, when the face is not square or rectangle, but rather a trapezoid, or an irregular shape, the bitmap used to fill the face is distorted. In order to correct the distortion, Papervision3D has a Boolean property precise. But how does it work?
Thanks! :)
I have this background that I'm using for a section, and it starts with a small arrow engraving at the top:
However I'm trying to get it when it repeats to clip out the top arrow part, just leaving the texture in the middle part. I was wondering if it was possible to do it with something like webkit? Thanks
You can't. You need to come up with another method of doing so. There are a number of ways to do this. Personally, I would use only the arrow, but use inner box-shadow for the shadows on everything else. This way you have smaller image being used, and it will always fit the size of the container.
Break up the background image from the pointer and make the two separate sprites. You can get tricky with the pointer and have it point in all 4 directions in the same image. This will allow you to pop up the bubble in all directions from the source.
You can't repeat both x and y on a usable sprite.
I have a maximum of three sprites in my projects.
One for non-repeating elements, another for repeat-x, another for repeat-y.
I find the clip property pretty much useless.
I have two images, a gameboard and the same gameboard with all posible player positions in a pressed state. When a player moves to a position on the board, I put the board image over the pressed board image and slice using context.drawImage() on the pressed image, to display the pressed position through the slice. However, my game board contains positions which are not rectangular but different shapes.
Is it possible with html 5 canvas, to cut a non-rectangular shape out of an image to display the underlying image?
I found it's possible to use clip() on shapes but I can't find a similar option on images.
you can create a third image that is a mask with transparent (alpha-channel) pixels and non-transparent pixels, and use a
globalCompositeOperation
to merge the mask and the to-be-masked image into a new image ( think you can use an xor or source-out here..
I'm working on a simple tutorial, and I'd like to randomly generate the positions of the red and green boxes in the accompanying images anywhere inside the dark gray area, but not in the white area. Are there any particularly elegant algorithms to do this? There are some hackish ideas I have that are really simple (continue to generate while the coordinates are not outside the inside rectangle, etc.), but I was wondering if anyone had come up with some neat solutions.
Thanks for any help!
Simplicity is a sort of elegance in its own right, so I agree with Jon: take a Monte Carlo approach and continue sampling until you get a valid value.
If you wanted to guarantee that you'd never place the red or green squares inside the white box, you could use the following simple algorithm:
Determine the height hS and width wS of the square you're placing.
Divide the gray area into 8 rectangular regions R = {R1, R2, ... R8}, defined by the white box. (Imagine a tic-tac-toe grid with the white box at the center; this defines the surrounding eight regions.)
Let P(S is placed in Ri) = A(Ri) / A(R), where A(Ri) is the area in which the center of S can be placed: that is, a region which is of area (hRi - hS) ยท (wRi - wS).
Select a region according to the above probabilities. Then select a point in that region from a uniform distribution of the available x- and y-coordinates.
Done!
I would personally go with the simple "keep sampling until you get a valid value" approach unless there's a chance that you'll have a very large white rectangle against a grey rectangle which isn't much bigger. To me, simpler is almost always better.
An alternative would be to work out how many possible pixels there will be, and generate a random number in that range. Then effectively number the pixels from top left to bottom right. Work out whether the given random sample is in the top section, the bottom section or the middle (which you can do by just seeing if it's less than the first pixel on the top line of the white rectangle, or less than the first pixel on the line below the white rectangle). Once you've worked that out, it's a simple matter of working out the row, then the pixel within the row. This isn't hugely hard, but it is pretty fiddly and easy to get wrong. Note that this is determining a single random pixel: as you're generating large squares, you should consider the range of valid pixels for the top left corner of the square, and find a sample in that range.