I have a scene with a background image (a lit room), and a black image (shadow) over that. I need to be able to move my finger over the background and reveal some parts of the scene, simulating a dim light source in a dark room.
My current approach was to generate a mask depending on the position of the touch, and then applying that mask to the shadow image. The problem is I'm generating a new mask and applying it every time I receive a touch event. It's a large image (800x600) and this causes the performance to go down and it increases a lot the memory usage, eventually crashing the game (I think I don't have any memory leaks, but that's not warrantied... anyway the performance itself isn't acceptable).
Can anyone think of a better approach (which doesn't involve using OpenGL ES -- that's not an option in this project) to do this?
To go with my comments above.
Maybe to get around the different shadow levels you could also have a grid of views (squares) between the image and the shadow view. each grid square has a different alpha opacity and when the spot is over a grid square, the grid square's alpha opacity changes to 0. when the spot moves off the grid square it's alpha opacity changes back to it's default.
Without more information it is a little difficult to know whether this approach will work in your case but what you could do is generate a single mask image, say, a radial alpha gradient and then apply an affine transform to it to shape it according to the touches. This can be used to simulate a torch/flashlight beam.
I would try this: use one view with a custom drawRect implemetation: first draw the shadow image (in grayscale) then a bright spot image in white an alpha. And finally the background image in a 'multiply' blend mode.
Just a thought, does the shadow has to be an image? Perhaps you could simply fill the shadow layer with a color and mask it then? This way the memory usage should be less and the effect should be nearly identical (if not exactly the same).
There is no reason to generate a new mask on every touch move. Instead, let the mask be initialized once and manipulate it (reset it's frame) as needed upon touch events.
Related
Pretend i have 3 nodes in total. One of the nodes is a large SCNShere and i put the camera inside this sphere and make the sphere double sided with a textured image. I then put in two smaller spheres next to each other in the center inside this sphere. I also allowCameraControl. I want to be able to zoom into these two smaller spheres without zooming into the larger sphere and messing up the detail on that sphere.
You can't put limits on the camera that's automatically created with allowCameraControl. You'll have to do your own camera management, using your own gesture recognizers.
Another solution would be to rethink your approach to the background image. Instead of using a sky sphere for the background (which is what it sounds like you're doing), use a skybox, or cube map. You can supply a cube map through the scene's background property. The SCNMaterial documentation explains the options for supply a cube map.
Hmm, I wonder what would happen if you use the large sphere's textured image/material as the scene's background, instead of putting it on an enclosing sphere?
I like the idea of using an image as the background but there are two problems. One is i looked on the web for ways to make an image the background and none of them work. Two I want the background to have depth so in order to go on that idea I need to find a way to zoom into the background and have the image pan in the opposite direction that I drag.
I've been searching around for this one for a bit, and unfortunately I can't seem to find any good, consistent results. So, in the Unity UI system, buttons can stretch without becoming pixelated or distorted. This is because the texture is split up into 9 parts - the corners, middle, and sides.
This works because the button's middle and sides are stretched, but not the corners. Then, the button appears not pixelated, at any dimension.
So, the question is as follows: How can I do the same thing for a transparent, unlit texture in 3D space? I have a speech bubble texture on a flat plane that I know how to re-scale to fit the text in the speech bubble.
I've set the texture type to Multiple Sprite, and divided it up into 9 parts. However, I cannot seem to find where I can set the texture to act like the UI button does, and I'm not sure that this is even possible in this way in 3D space.
Is there a way, or should I just make the different parts of the texture different objects, and move them together? That would seem very inefficient and ugly compared to this.
To accomplish what you are asking, you would need to create tiles for this speech bubble and then write a script that procedurally builds a speech bubble based on the plane's scale value. You could also try just changing the texture's Filter Mode to Point.
However I really don't think you should be using textures for this anyway. Why not just use a Unity Canvas and set the Render Mode to World Space? Then you can just set your text box to be a sprite, not a texture, and set its filter mode to Point (See below). This would also make it a lot easier for when you want there to be text in the speech bubble later on.
I'm trying to draw semi-transparent primitives (lines, circles) in OpenGL ES using Cocos2d but can't avoid the visible overlap regions. Does anyone know how to solve this?
This is a problem you usually come across pretty often, even in 3D.
I'm not too familiar with Cocos2D, but one way to solve this in generic OpenGL is to fill the framebuffer with your desired alpha channel, switch the blending mode to glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_DST_ALPHA) and draw the rectangles. The idea behind this is that you draw a rectangle with the desired transparency which is taken from the framebuffer, but in the progress mask the area you've drawn to so that your subsequent rectangles will be masked there.
Another approach is to render the whole thing to a texture or assemble the shape using polygons that don't overlap.
I'm not sure whether Cocos2D supports any of these…
I do not know what capabilities Cocos2D specifically provides, but I can see two options,
One, do not overlap like that, but rather construct more complex geometry such that each pixel is only covered once,
Two, use stencil buffer to create a mask as you draw, and to reject any pixels that are already masked.
I have to draw the following shape in a rectangle. What is the best way to do it? The blue areas are the background color. The black is a border and the red is the interior color. I want to paint the black and red only.
Thanks
It totally depends on how you would use the shape; whether they will move, how many of them will be displayed, whether they will be scaled while being displayed, etc.
In general, OpenGL ES is considered to be the fastest way of drawing on iOS devices. However, if you have only a small number of those shape (say, <10~100?) and the other part of the application does not have a lot of fast animations Quart 2D is usually enough in terms of drawing, in order to, say, achieve a 30/60Hz drawing rate.
How you use Quartz2D still matters a lot. If you need to redraw the shapes frequently, you would need to draw the shape on CALayers, and rather than redrawing the shapes, you should move and transform the layers.
Comparing drawing as a bitmap and a vector shape, I believe both would work fine for this kind of shape (especially because you would not redraw the shape so often, but only work with the layer on which the image already is drawn). But if your shapes are scaled frequently, you would consider vector images for the quality of the image.
To summarize, learn (if you don't already know) how to draw into a graphics context first (see Drawing and Printing Guide for iOS). You should be able to draw a simple vector shape or a bitmap image by overriding drawRect or similar methods inside a UIView object. Then if you need to animate those shapes, learn how to create a CALayer and draw on the layer (see Core Animation Programming Guide). Finally, if you need to create many duplicates of the shape on the screen, learn how to use CGLayer to replicate an image (see Quartz 2D Programming Guide).
I've got a pretty simple situation that calls for something I don't know how to do without a stencil buffer (which is not supported on the iPhone).
Basically, I've got a 3D model that gets drawn behind an image. I want an outline of that model to be drawn on top of it at all times. So when it's behind the image, you can see its outline, and when its not behind the image you can see a model with an outline.
An option to simply get an outline working would be to draw a wireframe of the model with thick lines and a z offset, then draw the regular model on top of it. The problem with this is obviously that I need the outline to be drawn after the model.
This method needs to be fast, as I'm already pushing a lot of polygons around - full-on drawing of the model again in one way or another is not really desired.
Also, is there any way to find out whether my model can be seen at the moment? That is, whether or not the image over top has an opaque section at the position of the model, or if it has a transparent section. If I can figure this out (again, very quickly), then I can just draw a wireframe instead of a textured model, depending on if it's visible.
Any ideas here? Thanks.
most of the time you can re-create stencil effects using the alpha channel and render-to-texture if you think about it ...
http://research.microsoft.com/en-us/um/people/hoppe/proj/silmap/ Is a technical paper on the matter. Hopefully there's an easier way for you to accomplish this ;)
Here is a general option that might produce the effect you want (I have experience with OGL, but not iPhone):
Method 1
Render object to texture as pure white, separate from scene. This will produce a white mask where the object would be rendered.
Either draw this directly to the screen with alpha fade for a "full object", or if you're intent on your outlines, you could try rendering THIS texture to another texture, slightly enlarged, then render the original "full object" shading over this enlarged texture as pure black. This will create a sort of outline texture that you could render over the top of the scene.
Method 2
Edit out. Just read the "no stencil buffer" stipulation.
Does that help?