Is there any way to draw a line using ID3DXLine with round endings? I am trying to draw a curve from number of line segments, but getting the empty areas where the line segments are connecting.
Performance here is essential.
Thanks!
Any other fast way to draw thick curved line using D3D?
You would be best off using a circular texture (with antialiasing around the edges) and then drawing half the texture at either end of the line. You can then render a strip through the center of the texture the whole way along a rectangle surrounding the line before finishing off with the other half of the texture at the other end. This will give you the effect you are after but its a tad more involved than simply calling "DrawLine" or whatever ...
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I have a WebGL scene that wants to draw both point and line primitives, and am wondering: Is it possible to draw multiple WebGL primitives inside a single draw call?
My hunch is this is not possible, but WebGL is constantly surprising me with tricks one can do to accomplish strange edge cases, and searching has not let me confirm whether this is possible or not.
I'd be grateful for any insight others can offer on this question.
You can't draw WebGL lines, points, and triangles in the same draw call. You can generate points and lines from triangles and then just draw triangles in one draw call that happens to have triangles that make points and triangles that draw lines and triangles that draw other stuff all one draw call.
Not a good example but for fun here's a vertex shader than generates points and lines from triangles on the fly.
There's also this for an example of making lines from triangles
How creative you want to get with your shaders vs doing things on the CPU is up to you but it's common to draw lines with triangles as the previous article points out since WebGL lines can generally only be a single pixel thick.
It's also common to draw points with triangles since
WebGL is only required to support points of size 1
By drawing with triangles that limit is removed
WebGL points are always aligned with the screen
Triangle based points are far more flexible. You can rotate the point for example and or orient them in 3D. Here's a bunch of points made from triangles
Triangle based points can be scaled in 3D with no extra work
In other words a triangle based point in 3d space will scale with distance from the camera using standard 3D math. A WebGL point requires you to compute the size the point should be so you can set gl_PointSize and so requires extra work if you want it to scale with the scene.
It's not common to mix points, lines, and triangles in a single draw call but it's not impossible by any means.
I would like to set the width of a line that I'm drawing in Metal. I can set the size of a point with point_size as explained here:
https://developer.apple.com/library/prerelease/ios/documentation/Metal/Reference/MTLRenderCommandEncoder_Ref/index.html
But, I'm not sure how it works with lines.
Short answer would be there is no way to control line width in the same way as a point size in Metal. Even in OpenGL graphics API, the function to do this (which used to exist as gllinewidth function) is now deprecated.
An option would be to draw the line as a quad (a box), with two triangles. This would let you control the width of the line.
If you want to stick to the line primitive itself, for some particular reason, the equivalent OpenGL question has been asked on StackOverflow already as seen here. The shader can be simple translated to Metal shading API.
If you're dead set on using lines instead of drawing a 2D box with two rectangles you can draw multiple lines next to each other. You can do that by drawing the same two vertices multiple times with one drawPrimitives call, just increase the instanceCount to simulate the thickness and then in your vertex shader function you could use your vertex_id and a modulus operation or some other type of logic to translate the position of the line to simulate thickness. This will probably be a lot easier than trying to do something fancy in a fragment shader.
If you are drawing multiple lines, multiply your instanceCount by the thickness you want and adjust your vertex shader function logic to place those additional lines next to each other.
I experimented with this and found this to be a pretty cumbersome process. As you need additional math to position the extra lines to thicken correctly. For example if you're drawing a horizontal line and want to increase thickness by two you'd want to modify the y value, but if it's vertical you'd want to modify the x. Drawing at an angle gets more complicated. You'll also run into issues trying to match lengths with widths if you're attempting to draw shapes.
I think it's much better to just draw two triangles to make a rectangle to fake a line. The math will be much easier and simpler to understand.
In Geometry, Euclid's lines do not have any width, they only have length, the width they get during drawing is simply for representation. So while I think lines may be good for debugging and development, like for displaying vectors or creating a grid to see scale, they're not what you want if you're trying to style them to present them to users. In that case it's the wrong tool for the job.
I want to draw a line with dynamic width as shown in attached picture. What should be the best approach for this. ?
Updated:
My task is to draw line on finger move. And the line width is changes as speed of swipe is change. both (Line width and finger swipe speed) are directly proportional .
As the image you posted doesn't has any consistent height-width proportion to calculate and change, i doubt this cannot be achieved.
In other solution you can draw a line of fixed pixel say 2 pixel and based on drawn length inflate the width if line till center and then again start deflate from center point to end point.
You need to see the difference between x coordinates otherwise if a sine wave is drawn with high nodes the line width will overlap each other.
Edited : This link might be of your interest then.You can modify it according to your need, its in cocos2d.
There is no direct support for variable thickness curves in iOS (or Mac OS for that matter.) The cocos2d project looks like a good approach.
There is also no support for soft-edged curves who's edges are feathered to transparent. I've thought about implementing a similar approach to the one outlined in the Cocos link using OpenGL. This would be a good application for a vertex shader, since it would take advantage of the parallel vertex processing and vector math available in shaders.
Take a look at this article Smooth Freehand Drawing. It might be helpfull.
You can manipulate with control points of
[path addCurveToPoint:pts[3] controlPoint1:pts[1] controlPoint2:pts[2]];
and fill the area between two bezierPaths. I am not sure if it will work, but you can try if you dont find anything else.
I'm building a thick line from triangles. The problem i'm having is that when the curve is semi transparent and some triangles overlap i get the effect in the picture. I would like for the triangles alphas to not get added.
I'm using this blend function:
glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_CONSTANT_ALPHA, GL_CONSTANT_ALPHA);
You may render the curve to separate render target with full opacity and then draw that target with custom alpha. Otherwise you should avoid overlapping.
you can use stencil test for blocking the drawing of already drawn fragments (which prevent blending from the first place)
I am trying to draw a series of squares in XNA. I am looking at all these articles about TriangleStrips and DynamicVertexBuffers. But, not sure where to begin.
Current step
I am able to draw 1 square using VertexPositionColor, TriangleList and indices. Now I want to draw a series of squares with varying colors.
End Goal
Something to keep in mind is the number of such squares that I would like to be able to draw, eventually. If we assume a 5px width, on a 1920x1080 screen, we can calculate the number of squares to be (1920 * 1080) / 25 = 82944.
Any pointers on how to accomplish this would be great!
Generally, you can draw more squares in the same way you draw the first one. However, there will be a significant loss in performance.
Instead, you can add all triangles to one vertex buffer / index buffer. You already are able to draw two triangles as a triangle list. You should be able to easily adjust this routine to draw more than two triangles. Just add the according vertices and indices to the buffers and modify the draw call.
If you need vertices at the same position with different colors, you need to add two vertices to the buffer.
This way, the performance loss is very little, because you draw everything with only one draw call. Although the amount of triangles should be no problem for most graphic cards, some smaller or older ones can get into trouble. If so, you should consider changing your drawing strategy. Maybe it is not even necessary to draw that much triangles. But you can think about that, if the resulting performance is too low...
If you don't care about 3D, just 2D - you can use SpriteBatch to draw squares/rectangles on the screen. This will handle batching all the vertex/index buffer management for you.