I'm creating an ios drawing app and would like to understand how to rotate the texture I'm using for drawing to have the texture follow the direction of my stroke.
Sketchbook for iOS and brushes are two apps that Ive seen accomplish this.
Does anyone have any idea of how to achieve this?
Here's an example of the concept that I'm trying to capture: http://drawsketch.about.com/od/learntodraw/ss/pencilshading_5.htm
Attached is a screenshot from the sketchbook app of this in practice.
UPDATE:
I was able to figure this out (thanks to SO community for helping out!) and posted my answer here: https://stackoverflow.com/a/11298219/111856
You can just rotate the brush texture as you're drawing it. You can get the angle by taking the arctangent of the y delta divided by the x delta for each segment of the stroke:
atan2(newY - prevY, newX - prevX);
Then rotate your brush texture by that amount before blending it at each point along the line.
Related
So what I want to do is build an image the size of the device. The image should be all blue except for a circle at coords (x,y) with a radius of z that should be clear, where x,y,z are variables. I know I should use the CGContext I just don't know how to get it done.
Ani ideas?
You want to use Core Graphics for this. To be more precise, read up on CGContext and the functions used to manipulate them. There are plenty of tutorials for it out there, and Apple provides a lot of sample code as well.
So I am trying to get a very basic "flashlight"-style thing going in one of my games.
The way I was getting it to work, was having a layer on top of my game screen, and this layer would draw a black rectangle with ~ 80% opacity, creating the look of darkness on top of my game scene.
ccDrawSolidRect(ccp(0,0), ccp(480,320), ccc4f(0, 0, 0, 0.8));
What I want to do is draw this rectangle EVERYWHERE on the screen, except for around a cone of vision that will represent the "light source".
What this would create would be a dark overlay on top of everything except for the light, giving it the illusion of a torch/light/flashlight.
The only way I can foresee this happening is by using ccDrawSolidPoly(), but since the position of the light source changes, so would the vertices for the poly.
Any suggestions on how to achieve this would be great.
You can use ccDrawSolidPoly() and avoid having to manually update vertices. For this you can create a new subclass of CCNode representing your light object, and do your custom shape drawing in its -(void)draw method.
The ccDraw...() functions will draw relative to the local sprite coordinates, so you can then move and rotate your new sprite to suit your needs and cocos2d will do the vertices transformations for you.
Update: I found out that you might be better off subclassing CCDrawNode instead of CCNode, as it has some facilities for raw OpenGL drawing (OpenGL's vertexArrayBuffer and vertexBufferObject internal variables and a buffer for vertices, their colors and their texCoords). If your stuff is very simple, maybe subclassing the plain CCNode is enough.
Could a png be used instead as a mask, as the layer above
Like that binocular vision you sometimes see in cartoons?
Or a filter similar to a photoshop mask that darkens as it grows outwardly to wards the edge of the screen
Just a thought anyway...
A picture of more of what your trying to explain might be good too
I am writing a small game (it is 2d) in IOS using Opengl as a way to get comfortable with opengl. I am using the Texture2D class from the CrashLanding demo. I am using this to generate text for the score. When the text is drawn it is upside down. In the code there is comments about the texture being loaded upside down but I can not find a way to render it the correct way. Any help would be greatly appreciated.
OpenGL and your image loading code do not agree on where the origin is. OpenGL starts in the lower left hand corner, while your picture starts in the upper right hand corner. You can apply a transform to the picture in your app like the CrashLanding demo does. Or even simpler pre flip the image in an editing program such as Photoshop. This will work if your image will only be used as an OpenGL texture in this app. If you need to display this same picture elsewhere you'll need to keep a non flipped version, or figure out how to apply the transform.
I'm looking to Animate a UIView and give it some 3D Effects.
I've experimented with CATransform3DMakeRotation() but can't seem to get the correct effect.
What I am trying to achieve is something like this:
Where the red view is moving from side to side with a 3d perspective.
Not the exact answer, but something to point you to right direction. Tumbljack has a nice tutorial, sample project and video on how to do 3D transformation on a view.
You can try with the following properties as mentioned in that.
layer.transform = CATransform3DMakeRotation(radian, x, y, z);
or
transform.m34 = 1.0 / -zDistance;
Try tweaking the sample code to get the desired output on your UIVIew. His tutorial is to have a complete 3D cube/sphere transformation and in your case you might need only the left and right movement from that.
Okay im working on making a tic tac toe game for one of my game development courses using XNA 4.0 I need to place sprites or some other objects so the game can check if the mouse is being clicked in the correct spots. I am going to use transparent sprites as a kind of button. How do I code them to go to these specific x,y coordinates. The game board is drawn on the background, I have all the coordinates to where to place these sprites. I am just stuck on putting the sprites in the correct positions.
SpriteBatch.Draw has a position parameter. Pass in an appropriately-valued Vector2.
Well if you check the Draw method you will find a parameter for the position.
Check this code sample
spriteBatch.Begin();
Vector2 pos = new Vector2(10, 10);
spriteBatch.Draw(SpriteTexture, pos, Color.White);
spriteBatch.End();
This is how you draw a sprite, with SpriteTexture as the image, on the position x10, y10 with the color White to modulate the texture.
You can also find more informations here.
Keep in mind that there are many overloaded methods to the Draw method. One you can even pass in rotation information and the like. So .Draw(...) has a lot of functionality you can use beyond just placing a sprite.