I've noticed that 3D engines tend to have more difficulty rendering curved lines (as in, it takes longer). Why does it use straight lines?
My Idea:
Have the engine use all curved lines, a curved line can be a straight line (i.e. a curved line with no curve) but a straight line can't be a curved line. Wouldn't this allow the engine to perform faster?
Correct me if I am wrong, but, what I'm saying is: Would it be better if the engine used curves instead of straight lines?
Related
The question is very simple. I just want to draw a simple circle around some part of an image with mouse. Not a fancy circle. It can be not at all a complete circle. I just want to circle around some part of an image to make it stand out inside the image.
As simple as this task is, I did not find any solution on google as it always proposes me very complex tasks like how to draw a circle and the like, which are not at all what I want. The problem is that Gimp is very powerful and so non-intuitive for very simple use cases. Any help will be appreciated as it will free me of doing all these changes under windows on another computer and sending the images via email and etc.
Quickest:
Make a circle selection with the Ellipse select tool (you can constrain it to a circle by depressing the Shift key after you start dragging).
Edit > Stroke selection (use preferably "Line" mode, that will also allow you to make a dotted line).
This said, to annotate images there are better alternatives.
I have a object that renders a grid of lines (used for a plot object I am working on) that will update frequently and shift all the lines around. If the grid will update at 60 fps would using CGContextFillRects or CGContextAddLineToPoint (rectangles vs lines) be more efficient?
Let's assume I am going to implementing things in a pretty efficient way. For example with the line technique I would use CGContextMoveToPoint and CGContextAddLineToPoint before stroking the entire grid line in one go with CGContextStrokePath. For both techniques I will generate the data required to draw my shapes somewhere other than the drawRect method.
Initially I feel like CGContextFillRects is better because it has less code involved in the actual drawing at the high level I am operating on so at a glance it seems more efficient. This said I don't need rectangles, and am really making lines in the end here so perhaps generating a rectangle would be more involved than my graphing processing should be when all I really need is a line. What do you all think? Lines or Rectangles for my fast moving/scaling grid?
Typically with computer graphics, drawing fewer pixels is preferable. CGContextAddLines looks like it accomplishes what you want, and might be shorter in code length than CGContextAddLineToPoint.
I am trying to draw arrows. I know how to draw lines which takes me half way there but I want the tip to have a small triangle just like an arrow. However even when I use a triangle as a point, obviously it does not always point towards the direction of the line and might sometimes produce weird looking arrows.
I would like to draw the passes a player makes on a soccer field. I do that using LINESTRING and 4 coordinates I have in a table in my database. I use the xFrom, yFrom, xTo and yTo coordinates and I manage to draw lines. However I would like to have the tip of the line to show as an arrow but I found nothing in Google or in SQL documentation.
I would like to use SSRS and not any other graphics vector program because its simpler and its incorporated easily in my overall report.
Anyone can suggest a way of turning a line into an arrow?
Thanks
Okay, first off I'd like to preface this answer with the statement that using SQL Server and Reporting Services as a graphics tool is asking for trouble. This is by far, not what it was meant for.
With that being said, I believe this would work. You will need to spend some time studying, though. When manipulating images, you have several operations that you can perform. (Like Rotating, skewing, resizing, etc.) The mathematics behind these operations can be performed using matrix algebra. What you will need to do is look at the line you have created. It has a slope. If you picture that line superimposed upon X and Y axes, you can see that there is an angle between the line and the Y axis. (Assumes that the triagle's base rests upon the X axis.) That angle is the angle that you will want to rotate your triangle that you're using as the tip of the arrow. That should fix your problem. You could create a formula to do the calculations. (If the formula engine is robust enough to handle matrix algebra.)
Here are a couple of pages that give you the basics of how to rotate an image.
http://datagenetics.com/blog/august32013/index.html
http://www.fastgraph.com/makegames/3drotation/
Good luck!
I am drawing a path into a CGContext following a set of points collected from the user. There seems to be some random input jitter causing some of the line edges to look jagged. I think a slight feather would solve this problem. If I were using OpenGL ES I would simply apply a feather to the sprite I am stroking the path with; however, this project requires me to stay in Quartz/CoreGraphics and I can't seem to find a similar solution.
I have tried drawing 5 lines with each line slightly larger and more transparent to approximate a feather. This produces a bad result and slows performance noticeably.
This is the line drawing code:
CGContextMoveToPoint(UIGraphicsGetCurrentContext(),((int)lastPostionDrawing1.x), (((int)lastPostionDrawing1.y)));
CGContextAddCurveToPoint(UIGraphicsGetCurrentContext(), ctrl1_x, ctrl1_y, ctrl2_x, ctrl2_y, lastPostionDrawing2.x, lastPostionDrawing2.y;
[currentPath addCurveToPoint:CGPointMake(lastPostionDrawing2.x-((int)furthestLeft.x)+((int)penSize), lastPostionDrawing2.y controlPoint1:CGPointMake(ctrl1_x, ctrl1_y) controlPoint2:CGPointMake(ctrl2_x, ctrl2_y)];
I'm going to go ahead and assume that your CGContext still has anti-aliasing turned on, but if not, then that's the obvious first think to try, as #Davyd's comment suggests: CGContextSetShouldAntialias is the function of interest.
Assuming that's not the problem, and the line is being anti-aliased by the context, but you're still wanting something 'softer.' I can think of a couple of ways to do this that should hopefully be faster than stroking 5 times.
First, you can try getting the stroked path (i.e. a path that describes the outline of the stroke of the current path) using CGContextReplacePathWithStrokedPath you can then fill this path with a gradient (or whatever other fill technique gives the desired results.) This will work well for straight lines, but won't be straightforward for curved paths (since the gradient is filling the area of the stroked path, and will be either linear or radial.)
Another perhaps less obvious option, might be to abuse CG's shadow drawing for this purpose. The function you want to look up is: CGContextSetShadowWithColor Here's the method:
Save the GState: CGContextSaveGState
Get the bounding box of the original path
Copy the path, translating it away from itself by 2.0 * bbox.width using CGPathCreateCopyByTransformingPath (note: use the X direction only, that way you don't need to worry about flips in the context)
Clip the context to the original bbox using CGContextClipToRect
Set a shadow on the context with CGContextSetShadowWithColor:
Some minimal blur (Start with 0.5 and go from there. The blur parameter is non-linear, and IME it's sort of a guess and check operation)
An offset equal to -2.0 * bbox width, and 0.0 height, scaled to base space. (Note: these offsets are in base space. This will be maddening to figure out, but assuming you're not adding your own scale transforms, the scale factor will either be 1.0 or 2.0, so practically speaking, you'll be setting an offset.width of either -2.0*bbox.width or -4.0*bbox.width)
A color of your choosing.
Stroke the translated-away path.
Pop the GState CGContextRestoreGState
This should leave you with "just" the shadow, which you can hopefully tweak to achieve the results you want.
All that said, CG's shadow drawing performance is, IME, less than completely awesome, and less than completely deterministic. I would expect it to be faster than stroking the path 5 times with 5 different strokes, but not overwhelmingly so.
It'll come down to how much achieving this effect is worth to you.
I need to paint the line which links two points.
I am doing it, in Java. I receive two points as parameters and I have to calculate if the straight line between them, is inside the black figure.
I developed my own solution using the straight line equation, but my results are different than using the "professional" programs (such as GIMP or even MS Paint).
Here is a example of what I want:
alt text http://img411.imageshack.us/img411/788/img1q.png
But my algorithm does this:
alt text http://img267.imageshack.us/img267/1908/img2d.png
*The green point is out of the figure and this is not possible.
Any ideas? Anyone know which code is been using for this, in "professional" apps?
Thanks!
Daniel.
EDIT: Images
It looks like you are truncating instead of rounding to the nearest pixel. Difficult to see on those small black ink splotches. Could you post the code?
"Professional" programs most likely use Bresenham's line algorithm.
Look at Bresenham's line drawing algorithm
Straignt lines are drawn using Bresenham's algorithm usually. I didn't get your point about green point being out of the figure - there's clipping to not waste time drawing outside the visible area.