I'm trying to answer this practice question:
Write a code segment that draws an X on the whole screen, using XGA frame buffers.
All i know is that you have to increment each x and y pixel by 1 to get a diagonal line.
If you are looking for resources on how to accomplish the drawing, you can look at this, this or this (if you like really bright colored text...). however, the point of a practice question (or homework) is for one to do ones own research.
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Having read the SVG2 draft, I am slightly disappointed to learn that there will be no new line caps than the standard 3. The new arc line join is brilliant however, but not what this question is about (I just wanted to mention that).
I had been hoping for a cap that ends in a triangle. But given my use case, that might not be ideal either.
As far as I can gather, Adobe Illustrator - which I do not use myself - allows the width of a stroke to be variable. This is useful when drawing from a drawing tablet, to highlight the pressure of the lines. It's true, this functionality exists in many bitmap drawing programs, but is there a way to achieve this effect in SVG, without having to draw multiple lines?
The idea is that each node should have a width, and the lines should then 'smoothly' scale the width between each node that had a different width.
Is this possible? And if not, could it be considered?
P.S. I should point out, that this is more a thought experiment and an idea than something that hinders my process. More of a nice to have than need to have.
While this may not be a true answer (SVG standard wise at least), it turns out that in the current trunk version of Inkscape, this feature called PowerStroke already exists. There are some screenshots of PowerStroke.
This should satisfy my quest for the time being.
It turns out - as well - that the arc line joins was actually suggested by Inkscape as well, they are just called extrapolate in Inkscape.
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 trying to make a C++ OpenGL representation of our Solar System as a way to teach myself OpenGL, so please keep your answers simple.
The problem I have is that planets are very far away, so everything else is beyond the clipping plane when viewing from any given planet. How do I move the clipping of C++ OpenGL 3.1 plane to, say, 2000000000? I'd prefer a simple code snippet if you can.
I've looked up SO and forum posts about this, but they're either so old that nothing applies (using legacy APIs or just dead links), or so complex that I can't work out what they're saying.
Clipping planes are defined by the perspective projection matrix.
If you use glFrustum, change the last argument passed to it to 2000000000.0.
If you use your own matrix, set 10th element of your matrix array to:
(2000000000.0+nearClippingPlane)/(nearClippingPlane-2000000000.0)
(the formula is (far+near)/(near-far))
and 14th to:
(-4000000000.0*nearClippingPlane)/(2000000000.0-nearClippingPlane)
(the formula is (-2.0*near*far)/(far-near))
2000000000 is very big value, however, so Z-fighting may occur if you add details such as mountains.
I need to draw an horizontal segment with dashes on it for a doc I'm writing.
I need to subdivide the segment length this way: given l, then length of the segment and n the fraction of the remaining length at each step, the first dash should be at first=l/n from the left, the second at 1/n + (l-first)/n and so on (until the division returns a number less than one)
What tool could I use to draw this automatically, without using a programming language?
Or... what script could do this?
I need and image in png/jpg as the final result.
if you need to do it programmitically, then maybe Logo programming language is your tool. it can also be done rather easily with LATEX and TikZ package, in this case you can consult with the TEX-LATEX site, also have a look at library for image creation, all the answers there link to usefull resources, which could be a bit overkill for what you need, but will work. if it's not have to be done programmiticaly, you can just create the image with Gimp or InkScape, though if you need to create many such dashed lines, it would be better to automate the process, and i don't know if these tools has batch action capability like photoshop.
I've been studying 3D graphics on my own for a while now and I want to get a greater understanding of just how everything works. What I would like to do is to create a simple game without using DirectX or OpenGL. I understand most of the math I believe, but the problem I am running up against is I do not know how to get control of the pixels being displayed in a window.
How do I specify what color I want each pixel in my window to be?
I understand I will probably run into issues with buffers and image shearing and probably terrible efficiency problems, but I want to create my own program so that I could see from the very lowest level, of the high level language, how the rendering process works. I really have no idea where to start though. I've figured out how to output BMPs, but I would like to have a running program spitting out 20+ frames per second. How do I accomplish this?
You could pick a environment that allows you to fill an array with values for pixels and display it as a bitmap. This way you come closest to poking RGB values in video memory. WPF, Silverlight, HTML5/Javascript can do this. If you do not make it full screen these technologies should suffice for now.
In WPF and Silverlight, use the WriteableBitmap.
In HTML5, use the canvas
Then it is up to you to implement the logic to draw lines, circles, bezier curves, 3D projections.
This is a lot of fun and you will learn a lot.
I'm reading between the lines that you're more interested in having full control over the rendering process from a low level, rather than having a specific interest in how to achieve that on one specific platform.
If that's the case then you will probably get a good bang for your buck looking at a library like SDL which provides you with a frame buffer that you can render to directly but abstracts away a lot of the platform specifics issues. It has been around for quite a while and there are some good tutorials to give you an idea of whether it's the kind of thing you're looking for - see this tutorial and the subsequent one in the same series, which should be enough to get you up and running.
You say you want to create some kind of a rendering engine, meaning desinging you own Pipeline and matrice classes. Which you are to use to transform 3D coordinates to 2D points.
When you have got the 2D points you've been looking for. You can use say for instance on windows, you can select a brush and draw you triangle values while coloring them at the same time.
I do not know why you would need Bitmaps, but if you want to practice say Texturing you can also do that yourself although off course on a weak computer this might take your frames per second significantly.
If you aim is to understand how rendering works on the lowest level. This is with no doubt a good practice.
Jt Schwinschwiga