I'm drawing irregular shapes using Core Graphics on a retina display. I do this by creating a UIBezierPath with 5 to 10 random points. In drawRect I stroke the path and fill it using solid red colour.
My problem is that diagonal lines in my drawing doesn't appear to be sharp.
I have tried anti aliasing but if anything this makes it appear worse. I have experimented with different line widths, not stroking, not filling, but I can not seem to get a really sharp diagonal line.
For comparison I created a similar shape in Photoshop (using similar size) and saved that as PNG. If I display that PNG on iOS it looks much sharper.
What can I do to make my shape that I create in code look sharp?
Make sure your CGPoint's are rounded to the nearest integer value.
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I am trying to add a transparent texture on top a cube. Only the front face is not transparent. Other sides are transparent. What could be the problem?. Any help is appreciated.
EDIT : I found that the face which is drawn first is opaque.
3 face of the cube is drawn.
Opaque face.((This face's index is given first in GLdrawElements))
Transparent face.
You most probably ran into a sorting problem. To display transparent geometries correctly the faces of the object have to be sorted from back to front.
Unfortunately there is no built-in support for that in opengl-es (or in any gfx-library in existance). The only possibility is to sort your polygons, recreate your object each frame and draw it with correctly ordered faces.
A workaround would be using additive transparency instead of normal transparency. Additive transparency is an order independent calculation. You have to remember to turn off z-buffer writes while drawing because otherwise some geometry may be ocluded.
Additive transparency is achieved by setting both blendfunc values to GL_ONE.
I would like to extract the white areas/bright areas of an image and place a custom objects in those areas. I need to know which framework to work with. if anyone has done something similar, I would appreciate an answer. I know how to get Pixel values, however the hard part is creating a Bloom/star effect in those highlighted areas.
You could make a mask where the luminance value was above a threshold, then blur or whatever the mask and composite above the image.
Say the user taps 4 spots on the iphone, defining an irregular 4 sided polygon (in 2d space). Is there a way to map/fit a (potentially highly distorted) image onto this shape, without using OpenGL?
Something like:
Is my only option to somehow calculate the 3d space that my irregular 4 sided shape sits in (based on where the tapped 2d points sit), create an OpenGL plane in that space, and map my texture to it flatly? Seems like there should be an easier way...
Thanks in advance.
Update: After diving into OpenGL I'm almost there... but I still can't get the texture to distort correctly. The triangulation seems to be messing with the texture mapping:
I can't answer your question completely, but one thing I would say is that you don't need to think about any conversion / mapping to 3D. Using OpenGL you can easily draw the shape in 2D and have the texture mapped as you desire. No need for any fancy maths or conversions. It's no more complicated than drawing a rectangle. OpenGL doesn't care that your 4-sided shape isn't actually rectangular.
I am building a cocos2d iPhone game.
There will be 6 'enemy spaceship sprites' that vary only by colour. I.e. all the sprites will have the same shape only some parts of the interior will have different colours.
My two options are:
1)
Create a template shape with a transparent interior.
At runtime, draw this shape on top of a small block of colour X.
The interior of the sprite will be colour X.
2)
Pre-render 6 different sprites
At run time, simply draw the sprite of a given colour.
What is the advantages and disadvantages of each method? Is there a best practice?
If I later wanted to animate the sprites, or dynamically change their colours, would this effect my choice of method?
Thanks!
I think first you need to figure out what it is that you're trying to do... Animation or a large number of color combinations make pre-rendering unfeasible. On the other hand, pre-rendering makes sense if you have a large number of ships on-screen at the same time, because you can use this technique to cut the number of drawing operations in half.
I am working on drawing anti-aliased lines in OpenGL-ES on iPhone. I am using an approach outlined in iPhone 3D Programming, called "Rendering Anti-Aliased Lines with Textures". The basis idea is to iterate through the line creating a bounding rectangle for each line segment (pair of vertices). This bounding rectangle can be represented by 6 triangles - and these can be filled with a texture. A texture (dot.png) comes with sample code, but I would like to experiment with other textures to see if I can get a more 3 dimensional affect.
So, I am wondering if there is a tool that would help me create these texture images. I have tried using Photoshop - but my skills there are rudimentary. I have seen "GIMP" mentioned, but I have no experience with it. I am guessing/hoping that there is some app out there that is designed for this purpose. Any pointers would be most welcome.
Thanks
If you mean, to create some blurry circles you can try to generate some using imagemagick. Some examples are here for blurring www.imagemagick.org/Usage/blur/
and here for radial gradients: http://www.imagemagick.org/Usage/canvas/#radial-gradient and www.imagemagick.org/script/fx.php