Is there a way to draw a line along a curved path with a gradient that varies in a direction perpendicular to the direction of the line? I am using the GDI+ framework for my graphics.
The simple answer is no. You can create a GraphicsPath in order to describe what you would like to draw, using AddPoint/AddLine/AddBezier and so forth as needed to describe the complex path of what you want to draw. When you draw the path you can provide a Brush which can be something like LinearGradientBrush or RadialGradientBrush. Neither of those gradient brushes reacts to the actual path being drawn in the sense of changing direction as the drawing occurs. You have to specify the angles etc as constant for the entire gradient area.
One possible method you can use is to set the clip region of the Graphics object to be that of the line only. Then draw a Linear Gradient over the extremes of the line e.g.
GraphicsPath gp = new GraphicsPath();
gp.AddArc(); // etc...
graphics.SetClip( gp );
graphics.FillRectangle( myLinearGradientBrush, gp.GetBounds());
The above code might give you what you are looking for.
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I need help, I have a matrix of pixels of values 0 to 255 and I need to plot them into image with plane curve.
Into this image I need to put a specific curve.
For example, I have a curve x=10+cos(t), y=10+sin(t) and a matrix of pixels m[i][j]. I need to show both in one image, looking like that:
I know I might need opencv, it's not problem, but I can't find myself writing the code.
You are showing a circle.
If you need to draw a circle, use the cv::circle drawing call.
API docs: https://docs.opencv.org/4.x/d6/d6e/group__imgproc__draw.html
If you need an ellipse, use the ellipse drawing call.
If you need to draw arbitrary polylines/drawContours, calculate the list of points and then use either of these calls.
OpenCV has a Plot2D class in the opencv_contrib repository/part of the modules. That's not parametric plot though.
I'm writing a drawing program that uses a pressure sensitive table for input. I'd like to be able to simulate the soft pencil effect that many other art programs have (such as Paint Tool SAI, Art Rage). Technique I'm using at the moment is functional, but is missing the cleanness I see in more professional programs.
My algorithm at the moment works like this:
Create a bitmap representing the head of the brush. This is just a transparent bitmap with a black circle drawn on it. The circle has an inner radius that is solid black and an outer radius. The blackness linearly fades from opaque to transparent as you move from the inner to the outer radius.
Capture input events from my tablet. Each point contains an (x, y) coordinate as well as a pressure value
For every point after the first one, draw a line from the previous point to the current one. This is done by drawing (daubing) the brush bitmap several times between the two points. The step size between each daub is chosen so there is an overlap between subsequent daubs.
This works reasonably well, but the result is a line that is somewhat blobby and jagged.
One thing I need to do is somehow smooth out the input points so that the stroke as a whole is smooth.
The other thing I need to do is figure out how to 'drag' the brush head along this path to make the stroke. If the spacing is too far apart, the stroke looks like a line of circles. If too close together, the stroke builds up on itself and becomes very dark. (I tried to fix this by attenuating the brush by the spacing. This does make things more consistent, but stops the stroke from being fully opaque).
Anyhow, I'd expect that there's a lot of research already done on this, if only I knew where to look. Please let me know if there are any better pencil drawing algorithms out there.
Instead of drawing the new circle over what has already been drawn, using the standard blending functions (so that regions of overlap get a higher opacity), you need to keep the maximum opacity so far.
Only after you have built up the complete stroke (as on a white sheet), you can blend it to the existing line art.
The picture illustrates the difference between blending and keeping the maximum opacity.
I'm trying to render lines (railroads, roads etc) onto a globe. At present, I'm using THREE.LineBasicMaterial and using the linewidth property to control thickness, but it would look much better if the thickness of the line at a given point was inversely proportional to the distance of that point from the camera.
Is such a thing possible (perhaps with a custom shader) or is the only way to construct a tube that follows the same path as the line? (And if so, what would the best approach be?)
I have an airplane. I use rectangle for bounding this airplane to detect collision and it works great. When the airplane begin falling down I rotate airplane's texture, but rectangle remains unchanged. I don't know how to rotate it. I need to rotate it with airplane's texture because my shell doesn't collide the airplane's tail and cabine.
How to rotate rectangle or perhaps create polygon shape to wrap all airplane? Any help will be appreciated!
#jellyfication's answer points to raycasting, but a different and also simple approach you could implement is the Separating Axis Theorem. The links below will show you in detail what the algorithm is about and how to implement it. They also have some interactive demos so you get the 'feel' for what the algorithm is doing.
http://www.metanetsoftware.com/technique/tutorialA.html
http://www.sevenson.com.au/actionscript/sat/
http://www.codezealot.org/archives/55 (this one has a lot of code)
http://gamedev.tutsplus.com/tutorials/implementation/collision-detection-with-the-separating-axis-theorem/
Good luck!
Use the polygon class to and draw your bounding Box.
Then within the polygon class there is a method to rotate.
Rotate and move the polygon with the plane.
I'm using GDI+ in my application, and I need to use a rotated LinearGradientBrush to paint several rects in the exact same way. However, although I'm calling the same code to fill each rect, the results aren't what I expect. Here's the code to create the gradient fill, where rcDraw is the rect containing the area to paint for each rect. These coordinates are in the parent window's coordinates, so they are not identical for the 2 rects.
g_hbrLinear = new LinearGradientBrush( Rect( 0, rcDraw.top, 0, rcDraw.bottom - rcDraw.top ),
clrStart, clrEnd, (REAL) 80, FALSE );
What I see on screen looks like this (http://www.nnanime.com/bugs/LinGradBrush-rotate10.png). You can see that it's as if the fill from the first rect continues into the second one. What I really want is to have the 2 rects look identical. I think I can do that if I paint each rect separately using its own client coordinates, but for the purposes of my app, I need to use the parent window's coordinates.
I guess what I'm asking is, how does GDI+ calculate the "origin" of a fill? Is it always based on 0,0 in the coordinate system you use? Is there a way to shift it? I tried TranslateTransform, but it doesn't seem to shift the fill in a way that I find predictable or understandable.
The rect passed to the linear gradient brush determines the where the left and right colors will sit, and the gradient will be painted within this rectangle.
So, I think you need to create a brush for each rectangle you are painting, where the rectangle you are painting is also passed to the constructor for the linear gradient brush.
My experience with the "transform" of linear gradient brushes matches yours; I haven't been able to understand what it's supposed to do.
You can think of a brush in GDI+ as a function mapping world co-ordinates to a color. What the brush looks like at a given point does not change based on the shape being filled.
It does change with the transform of the Graphics object you're drawing on. So, if you don't want to change the brush, you could temporarily change the transform of the Graphics object so that the rectangle you're drawing has a specific, known size and position in world coordinates. The BeginContainer and EndContainer methods should make this easy.
(There is also the RenderingOrigin property but it only affects hatch brushes, which oddly are unaffected by world transforms.)