I want to be able to darken (or lighten) objects farther away from the camera to provide some depth perception in my scene. I've looked into the ZBuffer example but this seems to only export an image of the z buffer (while simultaneously losing the color information), whereas I am looking to do something similar to this in real-time and retaining color in the scene.
Basically, how could I incorporate Z buffer information into the shading/coloring of the scene?
This blog article explains a shading method using the depth buffer called the Eye-Dome Lighting and also have an implementation in ParaView as an optional RenderView plugin. I think the idea is based on the use of the vtkDepthImageProcessingPass class.
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I'm new to glTF and I would have a very basic, and maybe naive, question. Sorry, and thanks for your understanding and your help.
We have a C++ application where we handle geometry primitive entities, like boxes, cones, cylinders, and so forth.
For visualizing the geometry entities we currently use Coin3D, which have corresponding geometry shapes: Box, Cone, ...
We now would like to add a glTF exporter too, and I have started to explore the glTF specs.
I must say, in the official documentation, and on the web, I could not find any support in glTF for basic geometry shapes.
Therefore, my questions are:
is that true, that glTF has no notion of, let's say, a Box, or a Cone? Or did I missed something obvious?
If the answer to 1) is "NO", are there tested/supported/suggested implementations for basic shapes? I have only found some "example" shapes, like the Box here; but I could not find any collection of implementations of basic shapes. Again, did I miss something?
Are there any best practices, or documentation, on how to implement basic geometry shapes in glTF?
The short answer is you're correct, glTF does not currently store basic geometric shapes directly as a box, cone, cylinder, etc. The format is intended to be a runtime delivery format, not an asset interchange format.
As such, the internal data structures within glTF are designed to mimic the raw data that would typically be fed into a GPU using a graphics API such as OpenGL, WebGL, etc. Entire blocks of glTF data can often be pulled off a disk or network and handed over directly to a graphics API for rendering, with minimal pre-processing.
This means that all of your basic shapes must arrive as the GPU expects to find them: triangulated. Even a simple box is made up of twelve triangles, and because the sides don't share normal vectors, the normal "vertex attributes" are different, hence triangles from different sides of the box don't share vertices (again, because the GPU wouldn't accept that as a raw input). The benefit is that a WebGL client doesn't have to think very hard about what to do when it receives a glTF, it can just start cramming data into the graphics pipeline to get things moving.
For a broader overview, the ever-popular glTF - What the Duck diagram is widely considered an excellent starting point, and the glTF Tutorials are a good follow-up to that.
I would like to create an image in Haskell using the Rasterific library and then display that image in a GTK window; the Rasterific library lets me generate an RBGA-formatted 32-bit pixel depth image, but I am having trouble figuring out how I can take this raw image and display it in a window or drawarea or whatever in GTK.
(I've spent a lot of time looking through the documentation, but I've been having a hard time seeing how to fit the parts together, especially since the Haskell documentation is often non-existent and at some point the cairo library gets involved in a way that's not entirely clear to me.)
I wrote a package called AC-EasyRaster-GTK for this exact purpose.
It's a wrapper around gtk2hs. That library gives all the necessary parts, but it's not actually all that easy to figure out. So I wrote a library so I wouldn't have to keep looking this stuff up!
ib_new gives you a new image buffer, ib_write_pixel lets you write a pixel, and ib_display will start the GTK event loop, display the bitmap in a window, and block the calling thread until the user clicks close. Sadly, there's no easy way to chuck an entire array at GTK. (It demands a particular pixel order, which varies by platform...)
I'm sure there's a better way to do this, but I'm not finding it either. You can iterate over all the pixels in the original image using something like forM_ (range ((0,0),(w,h))) and draw them onto a Cairo drawing using something like this: (The Cairo calls are correct but I'm just guessing about the Rasterific functions)
drawPixel color x y = do
setSourceRGBA (red color) (green color) (blue color) (alpha color)
rectangle x y 1 1
paint
I am experimenting with creating GUI and graphics based applications in Haskell using gtk2hs and cairo. Currently I am working on a program where a user can create and manipulate simple geometric shapes on screen.
The three manipulations I want the user to be able to do are: translation, rotation and scaling. The ideal implementation of this would have the transformation handles present in most image manipulation programs such as photoshop:
(i.e Where the object can be translated by dragging somewhere inside it, scaled by dragging the appropriate white box, and rotated by clicking and dragging in the direction of rotation outside of the object's box)
I cannot find a simple way of doing this "out-of-the-box" in either the gtk or cairo documentation, and have been unable to find a suitable library by searching on google. Does anyone know of a Haskell API which would allow me to manipulate graphics in this way or, failing that, know how I would go about implementing my own version of this type of functionality in Haskell?
There are not built-in widgets for this; you'll have to build it yourself by drawing all the appropriate elements (e.g. the actual shape, a bounding box or similar, rectangles on the corners and edges of the bounding bex, etc.) and handling mouse events by checking whether the events fall on these elements or not. It should not be difficult... though it may be a bit tedious.
I have been using the Gloss Library for some game programming, and have got to the point where I am having the most difficulty laying out different elements on the screen. I was wondering whether it was possible to limit a Picture type to display only a certain rectangular area of the screen. The library already has the concept of a rectangular area with the Extent type, but there does not appear to be any way to 'subtract' from pictures.
If there was a way of doing this then it seems like creating a View type or similar that takes over responsibility for a certain area of the screen — which can also contain additional views, and with suitable coordinate substitutions between them etc — would be an achievable and sensible goal. But without a way to limit drawing areas it doesn't seem like this would be possible within the Gloss framework.
It seems that clipping is not supported in Gloss.
Nevertheless the recursive drawing of views each with their own relative coordinate system does still seem to be a viable and useful goal, and I am part way through writing code for this now.
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