Develop Reference

OpenTK/C# - 2D text rendering works, how about 3D?

Edit: Bad angle picture was due to Depth Testing. Still need the 'right' way to do 3d text rendering though!
I got 2D text rendering in OpenTK working. It's very simple, I use .NET Graphics class methods to draw a string to Bitmap, which I can load into GPU via OpenTK. Ok great, but how about 3D?
I'm thinking about this in terms of a cylinder. What is a cylinder? It's just a circle stretched out over a certain height. That's EXACTLY what I want to do here! I researched a bunch...but surprisingly there isn't all that much info readily available IMO for such a basic task.
Here's what I've tried:
1) Rendering the bitmap 100 times from Z = 0.0f to 1.0f. This actually works pretty well! For certain rotations anyway.
2) Drawing 16x16x16 Voxels (well, I think I'm drawing voxels). Basically the idea is, use the typical GL.TexCoord3 and GL.Vertex3 methods for drawing the SURFACE of a cube, but because we are drawing so freakin many of them, I figured it would actually give depth to my text. It sort of does, but the results are actually worse than attempt 1.
I want to get this working with a really simple solution, if one exists. I'm using Immediate mode, and if possible I'd like to keep using that.
This is what solution 1 looks like at a good angle:
Bad Angle:
I know that my method is inherently flawed because these bitmaps dont actually have a depth when I draw them, which is why at some critical angles either the text becomes flat looking, or disappears from view.

Depth Buffer not working

In my XNA 3D game, for some reason, the depth buffer is off and ignored - even though I've done everything I can find to enable it (which admittedly isn't much, but it's supposed to be simple... not to mention default)
Before the models are rendered:
global.GraphicsDevice.DepthStencilState = DepthStencilState.Default;
Somewhere earlier:
graphics.PreferredDepthStencilFormat = DepthFormat.Depth24Stencil8;
graphics.ApplyChanges();
the models are rendered using a Vertex/Index list with device.DrawUserIndexedPrimitives and a BasicEffect.
It comes out like this:
The purple object is very far from the camera, and is drawn 1st.
The gray object is very near the camera, and is drawn 2nd.
The blue object is medium-distance to the camera and is drawn 3rd.
The gray object is rendering behind the blue object - that is correct if you're going off the draw order, but I want it to organize by distance from the camera (Using the depth buffer), in which case the gray object should draw in front of the blue object.
(And, no, just quickly sorting them manually, while it may provide a temporary solution, is not the way to fix this problem)
Update: This is directly related to the fact that I'm rendering onto a RenderTarget2D instead of straight onto the screen. (If I render on-screen instead of to the rendertarget, the depth is calculated correctly. The rendertarget is needed for other parts of the program... or an equivalent system.)

Well I found what I missed on my own after searching randomly:
A RenderTarget2D has its DepthBuffer disabled by default.
I just had to set the DepthFormat on the rendertarget I was drawing too.
Knew I missed something obvious...
(I'll green-check-mark-this in 4 hours when the site lets me.)
ED: that is, unless, in that time, somebody posts a nice list of everywhere XNA depth buffer data could/should be set, to better help people who might find this topic by google.

Making a lightsystem like Terraria?

I am trying to make my lighting similar to Terraria's, block-lighting. Now, I know how to make blocks darker, I can assign blocks to a certain lightlevel, but, how would I make an actual light entity, that emits light in a round shape (Can be diamond-shaped too)?
Help would be greatly appreciated, also, if I wasn't clear in my question, feel free to ask.

Basic 2D lighting is very simple. Just do a distance check from your block, to your light, and use that value to scale your light.
This is something you could do fairly simple, since Spritebatch.Draw has a nice Color tint parameter [link]
A pseudo function could be
distance = (block.position - light.position). Length();
lightPower = distance / light.MaxDistance;
finalTint = light.Color * lightPower;
Render Block, with finalTint
For more nice looking light, you could replace "distance / light.MaxDistance" with a more smooth effect.
If you also want lights to go through a few blocks like Terraria, you could count all blocks between your block and the light source. Scale your lightPower down by that amount, and you get the same effect like Terraria has.
Of course, this is a non optimized way of doing it, but should work.
The latest Terraria version however seems to have smooth per pixel lighting instead of per block [preview]. For that I assume they used a second render target and/or Pixel Shader to keep fast performance. This could be a little difficult if you are not familiar with rendering pipelines though.
Hope this helps!

I'm working on a game with a similar lighting model, and the way we do it is this:
Draw the scene, without lighting, to a render target (called the 'Scene Buffer')
Draw the scene's lights, represented as grayscale gradients of any required shape, to a second render target (called the 'Light Map')
Draw the Scene Buffer to the screen, passing in the Light Map as a parameter to the pixel shader
In the pixel shader, query the value of the Light Map at each pixel and adjust the color of the final pixel up or down as necessary.
This also gives you the ability to have colored lighting; all you have to do is tint the light gradients that you render to the Light Map. Just remember to use additive alpha blending.
The downside of this approach is that it's rather naive, and provides no easy way to occlude the lights (that is to say, they pass through walls). In our case, this isn't an issue; you might decide otherwise.

WPF: Finding 3D-visuals that are partially inside a 2D rectangle

I am making a WPF program with the possibility to modify data graphically in 3D. In order to give the user the option to select multiple graphical objects at the same time, I want to implement a selection rectangle. (Just like the one in windows explorer.) A common functionality in programs like this one is to have 2 different functions for the selection rectangle, and that the user can somehow choose which of the methods should be used.
Any object that is partially or completely inside the rectangle is selected.
Only objects that are completely inside the rectangle are selected.
The 2nd method is straight forward by using the bounding box of each object, and check if it is inside the rectangle. The 1st one on the other hand, seems to be quite some work. All my graphical objects are complicated 3D figures, and can be rotated by the user in any way. At the moment I am unable to find any other way than checking if any of the triangles in the mesh of any of the objects cross my 2D rectangle, and that can be quite time consuming.
I have little experience with WPF 3D, but I have done this before in OpenGL. Then I could tell OpenGL to draw a specific area of the screen, and the collect a list of objects that was visible in the specific area. All I needed to get the functionality I wanted was about 5 lines of code.
I guess my question is this:
Is there a way to do this with WPF 3D, similar to the OpenGL approach?
If not, is there any other smart way to find all objects (Visual3D) in a viewport that is partially behind a 2D rectangle?
I refuse to believe I am the only one with this kind of problem, so I hope a clever mind can point me in the right direction.
Regards,
Sverre
Thank you for your answer!
The 2D-rectangle is just in front of the camera and extending infinitely forward. I want to get any object that is partially or completely inside that frustum.
The camera we are using is an orthographic or perspective projection camera (System.Windows.Media.Media3D.ProjectionCamera). The reason we are not using the matrix camera is that we are using a 3rd party tool that does not support the matrix camera. But I am sure there is a way to get the matrix from a projection camera as well, so that is hopefully not the problem.
In theory your solution sounds like just what we need, but I am not sure how to proceed. Do you have any links to sample-code, or can you give some more hints on how to actually implement this?
Btw: Since we are working with WPF, we do not have direct access to DirectX. At least that’s what we have concluded after some research. You mention use of the z-buffer, which we haven’t been able to access through WPF. If you know a way to access the z-buffer, it’s greatly appreciated! This is of-topic, but we have struggled to disable the z-buffer for some time, but have given up…
Best regards,
Sverre

Is your intersection region a 2d rectangle or a frustrum based at a 2d rectangle and extending infinitely forward (or perhaps to some clipping limit)? If it can be construed as a viewing frustrum, then you can leverage the existing capabilities of the graphics system to render the scene using a Camera View and Projection that corresponds to your originating rectangle, with all lighting and shading disabled and colors chosen specifically to 'tag' the different objects in your scene. This means you can use the graphics hardware to perform the clipping/projection as a 'rendering' operation, then simply enumerate the pixel values as 'tags' to determine the objects present in the rectangular view.
If you need to restrict selection to an actual 2d slice (or a very shallow frustrum), you can use the Z-buffer (if you can get access to it) to exclude tagged pixels that are outside the Z range of your desired selection frustrum.
The nice thing about this approach is that you probably already have the Camera matrix (it's the same matrix used for your window for selection) and only need to change the Projection matrix to be a sub-set of the viewing window.

A 'smart' way would be to transform the rectangle into a box using the Camera's matrix
And then do a intersection of all the objects and the box.

.NET high level graphics library

I am programming various simulation tools in C#/.NET
What I am looking for is a high level visualization library; create a scene, with a camera with some standard controls, and render a few hunderd thousand spheres to it, or some wireframes. That kind of thing. If it takes more than one line to initialize a context, it deviates from my ideal.
Ive looked at slimDX, but its way lower level than im looking for (at least the documented parts, but I dont really care for any other). WPF perspective looked cool, but it seems targeted at static XAML defined scenes, and that doesnt really suit me either.
Basically, im looking for the kind of features languages like blitzbasic used to provide. Does that exist at all?

I'm also interested in this (as I'm also developing simulation tools) and ended up hacking together some stuff in XNA. It's definitely a lot more work than you've described, however. Note that anything you can do in WPF via XAML can also be done via code, as XAML is merely a representation of an object hierarchy and its relationships. I think that may be your best bet, though I don't have any metrics on what kind of performance you could expect with a few hundred thousand spheres (you're absolutely going to need some culling in that case and the culling itself may be expensive if you don't use optimizations like grid partitioning.)
EDIT: If you really need to support 100K entities and they can all be rendered as spheres, I would recommend that you bypass the 3d engine entirely and only use XNA for math. I would imagine an approach like the following:
Use XNA to set up Camera (View) and Perspective matrices. It has some handy Matrix static functions that make this easy.
Compute the Projection matrix and project all of your 'sphere' origin points to the viewing frustrum. This will give you X,Y screen coordinates and Z depth in the frustrum. You can either express this as 100K individual matrix multiplications or multiplication of the Projection matrix by a single 3 x 100K element matrix. In the former case, this is a great candidate for parallelism using the new .NET 4 Parallel functionality.
If you find that the 100K matrix multplications are a problem, you can reduce this significantly by performing culling of points before transformation if you know that only a small subset of them will be visible at a given time. For instance, you can invert the Projection matrix to find the bounds of your frustrum in your original space and create an axis-aligned bounding box for the frustrum. You can then exclude all points outside this box (simple comparison tests in X, Y and Z.) You only need to recompute this bounding box when the Projection matrix changes, so if it changes infrequently, this can be a reasonable optimization.
Once you have your transformed points, clip any outside the frustum (Z < 0, Z > maxDist, X<0, Y<0, X>width, Y>height). You can now render each point by drawing a filled circle, with its radius proportional to Z (Z=0 would have largest radius and Z=maxDist would probably fade to a single point.) If you want to provide a sense of shading/depth, you can render with a shaded brush to very loosely emulate lighting on spheres. This works because everything in your scene is a sphere and you're presumably not worried about things like shadows. All of this would be fairly easy to do in WPF (including the Shaded Brush), but be sure to use DrawingVisual classes and not framework elements. Also, you'll need to make sure you draw in the correct Z order, so it helps if you store the transformed points in a data structure that sorts as you add.
If you're still having performance problems, there are further optimizations you can pursue. For instance, if you know that only a subset of your points are moving, you can cache the transformed locations for the immobile points. It really depends on the nature of your data set and how it evolves.
Since your data set is so large, you might consider changing the way you visualize it. Instead of rendering 100K points, partition your working space into a volumetric grid and record the number (density) of points inside each grid cube. You can Project only the center of the grid and render it as a 'sphere' with some additional feedback (like color, opacity or brush texture) to indicate the point density. You can combine this technique with the traditional rendering approach, by rendering near points as 'spheres' and far points as 'cluster' objects with some brush patterning to match the density. One simple algorithm is to consider a bounding sphere around the camera; all points inside the sphere will be transformed normally; beyond the sphere, you will only render using the density grid.

Maybe the XNA Game studio is what you are looking for.
Also take a look at DirectX.

WPF perspective looked cool, but it seems targeted at static XAML defined scenes
Look again, WPF can be as dynamic as you will ever need.
You can write any WPF program, including 3D, totally without XAML.

Do you have to use C#/.Net or would MonoDevelop be good enough? I can recomend http://unity3d.com/ if you want a powerful 3D-engine.