I'm using SDL2 to draw a couple of polygons on a window for a simulation I'm doing. I'm using SDL2_gfx primitives for drawing polygons, but now I want the polygons to be rotated. What is the easiest way to achieve this? Performance is not terribly important at the moment. I'd just rather not to dirty my hands with trigonometry!
SDL2_gfx includes this functionality as standard. It is found in 'SDL_rotozoom.h' and documentation of the use of functions from it can be found at the link below:
http://www.ferzkopp.net/Software/SDL_gfx-2.0/Docs/html/_s_d_l__rotozoom_8h.html
Related
Problem
Hi,
So I have noticed that software like Microsoft Edge and OneNote and Notability, store hand drawn strokes as vector curves or lines. They also provide the ability to erase strokes, by dragging the eraser over them.
I wanted to implement something similar in my software, an SVG Animation and Creation bundle, and I have come up with the logic for the freehand stroke to SVG curve, a demo is available here:
https://phantomzback.github.io/SvgFreehandDrawDemo/polylineTest.html
It uses the polyline tag with the cursor positions, and path simplification is something I also plan to implement. But before that, I need a way to detect if the eraser has gone over the stroke. I have an approach but I am not sure how great of an approach it is. I'd appreciate advice on how this can be improved or alternative methods to tackle the problem.
Current Idea
Find the pixels where the stroke is rendered, and save it in an array. Then, check for if the eraser tool is active and goes over that stroke. If it does, delete this stroke.
Finding the pixels shouldn't be very hard since a polyline is a bunch of points and lines drawn between them. But I plan on adding support for paths later, for which a better approach might be needed.
Thanks in advance!
is there a way to render arbitrary polygons with n > 3 corners in directx 11?
i remember this being possible in older OpenGL versions with GL_POLYGON but i haven found anything in the directX API for this.
The answer is not natively, there is no NGons primitive types, and the GL ones were mostly full of issues and quite near of a FAN.
You will have to triangulate yourself, it can be done with a geometry shader, receiving the control points and outputing the triangles
A compute shader with a DrawIndirect is possible and more versatile but need more setup to work.
I saw an infographic online that I wanted to use as a challenge to learn d3.js. The original infographic is here:
http://www.shah3d.com/wp-content/uploads/2012/11/IG-WWF-Dehahs.png
I've made a start here:
http://www.tips-for-excel.com/d3test/arc/arc%20test.html
You'll notice that the original has nice lines that link an arc from the bottom with an arc along the top. So far I can only think of painfully placing lots of circles to achieve this effect, hence the odd red circle currently in my visual. What would people's best methods be to replicate the original graphic? Which element would make this task easier? Arcs? Lines? I imagine I'll have to manipulate my data so that the lines go where they're meant to.
Happy to give more info if needed and thanks for taking time to read this.
There are a few existing diagrams to work off of from d3's galleries:
http://bl.ocks.org/4062006
http://bost.ocks.org/mike/uberdata/
Both use the length of the chord as the width of the stroke (initially), but you can tinker with that, for sure.
Graphically, you could use arcs, or full circles with a clip around it. As to the 'best' way to do it, that may come out of 'requirements' of how your graphic needs to behave (animation, relative arc placement, etc).
Personally, I'd go with path arcs.
I'm working on a game using OpenGL displaying sprites, i.e. 2d quad-mapped graphics with no projection, that will be displayed on several different resolution screens. (i.e. iPhone retina/non-retina, iPad.. my next project the problem will expand to desktop resolutions which are far more numerous)
I'm OK with handling different aspect ratios, that can be handled by opengl and my placement of the sprites. I'm also OK with slightly different resolutions - use same art and either border the screen, or display a little bit more info.. but when things start to grow/shrink by like 50%+ it's a major issue.
What is standard procedure for generating the art assets in this situation? Generate for the largest resolution and just let OpenGL worry about resizing during it's rasterizing, or do people generate art sets for each main resolution?
Rasterized sprite art tends to get ugly when it's stretched (interpolated), so I'm concerned.. but generating different sizes really means for practical purposes I have to go with vector drawings and export several resolutions. Limits the artist and is somewhat complicated as far as loading and managing the assets
(Yes, I can "just try it" to an extent, but I already have an idea of the results. I'm looking for solutions people use and angles I maybe wouldn't have thought of. This question does have an answer(s) it's not subjective or lazy)
You are correct that scaling bitmaps tends to make sprites bad. There are a couple of ways of dealing with that:
Draw them (pixelart) at all required resolutions. That is a lot of work but gives you full control.
Draw them (vectors) and render them at all required resolutions. Less work but scaling up or down beyond 50% or 200% might give bad results.
Draw them (3D appliction) and render them at all required resolutions. Quite some work but a very consistent set of sprites.
For each of these options you are free to post-process the bitmaps to clean them up or add details but if you do this for options 2 and 3, you are breaking the chain and will have to apply the changes again when rendering the same set again.
An other option is to limit the variation of resolutions.
As far as I know it is very common in the (game) industry to make all (or the most used/visible) sprites as pixel perfect as possible. This is what they pay the artists for...
I'm using RaphaelJS to implement some event-heavy SVG. I have a set of paths on a canvas, and a point. How can I get all the paths that cross that point? Relatively new at this, but I assumed this would be trivial and I can't find anything about it.
If it helps, the specific implementation is trying to detect on the mousedown event if I've clicked on a path so I can rotate it around another point onmousemove.
Unfortunately, I'm not aware of a portable (supporting both the SVG and VML backends of raphael) way to do this without implementing the math yourself. However, for browsers that support SVG, the SVG spec includes built-in support for exactly what you are requesting:
http://www.w3.org/TR/SVG/struct.html#_svg_SVGSVGElement__getIntersectionList
Vector is math. Find the equations of the lines and see if the point fulfill the equation.