OpenTK - Forums

Procedural Figures?

Zsar — Fri, 17 May 2013 09:19:20 -0700

I would like to pass a function like "f(x):=(y=x+1; z=x-1)" or "f(x, y):=(z=x+y)" or "f(x0):=(x++; y=x+x0; z=x+z)", a precision identifier, say 1000 or 0x3 for three decimal places, an optional limit to recursion depth and be done with it, as the manual advises to keep the number of GL calls to a minimum - and to pass any of (potentially very large) n values "manually" when I could just pass the function which generates these values seems to be supremely wasteful.

The relevant manual entry is empty.
The quick start file shows how to add figures per vertex. Methods to construct figures by vector are easily found within the API.
How would one add a figure by function? Is the obvious solution: compute-vertex-or-vector-and-insert-loop; the only one?

GL.Uniform4 call results in InvalidOperation error

jodev — Tue, 14 May 2013 04:48:23 -0700

Hi all,

I've been pulling my hair out on an issue that has me stumped. I'm very much a OpenGL beginner and I'm trying to figure out why this code fails. I've tried to isolate all relevant parts, but if you need to know more please let me know.

case GLTStockShader.Identity:
                    iColor = GL.GetUniformLocation(uiStockShaders[(int)nShaderID], "vColor");
                    vColor = uniformList[0] as float[];
                    GL.Uniform4(iColor, 1, vColor);
 
// debug info
                    string vColorSummary = string.Join(", ", vColor);
                    System.Diagnostics.Debug.WriteLine("iColor        = {0}", iColor);
                    System.Diagnostics.Debug.WriteLine("vColor        = " + vColorSummary);
                    System.Diagnostics.Debug.WriteLine("GL.GetError() = {0}", GL.GetError());
                    break;

This outputs the following debug info:

iColor = 0
vColor = 1, 0, 0, 1
GL.GetError() = InvalidOperation

The vertex and fragment shaders are defined as follows:

const string szIdentityShaderVP = "attribute vec4 vVertex;\n" +

Intel_map_texture (or general extensions loading)

wheelinlight — Tue, 14 May 2013 00:30:21 -0700

Im trying to use the INTEL_map_texture extension. I can't find this in the OpenTK API so I guess I have to retreive it myself. Or is there any other way I can do it?

This is how my code looks now, but I only get a null pointer back. I have checked the computer with OpenGL Extensions Viewer and it says it should be in there.

wglGetProcAddress("MapTexture2DINTEL");

Any suggestions?

Problem with texture loading

croman102 — Sat, 23 Mar 2013 12:03:27 -0700

I decided to move my project to OpenTK from TAO framework (btw, thank you for the great library). My problem is in my loading textures class. It says that the problem is in the 42nd line.

            int openGLId = Ilut.ilutGLBindTexImage();
 
            System.Diagnostics.Debug.Assert(openGLId != 0);   // line 42

---- Assert Long Message ----

at GameLoop.TextureManager.LoadTexture(String textureId, String path) in C:\Users\Korisnik\Documents\Visual Studio 2010\Projects\Idezasada\Idezasad\TextureManager.cs:line 42

Thank you!

How to render a processed image?

Robbepop — Mon, 08 Apr 2013 17:39:13 -0700

Hiho,

I am very new to OpenTK and to GPU programming in general and have already read through many OpenTK/GL tutorials, however I am currently stuck at getting my code working.

Basically, I am trying to read out images (Bitmaps) do some image processing with them and display them on my screen - so no 3D but only 2D OpenGL features are needed.
At the moment not a single image is displayed and I am not even aware what steps are working at all but what I can say is that my whole code runs through all stages without exceptions etc. ...

Here is what I have wrote, copied, brainstormed so far:

My initialization codes.

        int vertexShaderObject, fragmentShaderObject, shaderProgram;
        int vertexBufferObject, colorBufferObject, elementBufferObject;
        int currentTextureId;
 
        private void SetupViewport()
        {
            int w = glControl1.Width;
            int h = glControl1.Height;
            GL.ClearColor(Color.Black);
            GL.MatrixMode(MatrixMode.Modelview);
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();

Loading .obj models

Memory Leak — Sun, 28 Apr 2013 06:11:38 -0700

I have attempted to write a program which parses a .obj file and 'should' display it. However once the program is executed the product is just a blank display screen. I only started with openGL today so there is probably something obvious I'm looking over :p

Form1:

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void glControl1_Load(object sender, EventArgs e)
        {
            GL.ClearColor(Color.Black);
 
            glControl1.Paint += glControl1_Paint;
        }
 
        private static void setUpCamera()
        {
 
 
        }
 
        private void glControl1_Paint(object sender, PaintEventArgs e)
        {
            double aspect = glControl1.Width / (double)glControl1.Height;
            GL.Clear(ClearBufferMask.ColorBufferBit);
            GL.Clear(ClearBufferMask.DepthBufferBit);
 
            //'Basic Setup for viewing
            Matrix4 perspective = Matrix4.CreatePerspectiveFieldOfView(MathHelper.PiOver4, (float)aspect, 0.0001f, 5000.0f); //'Setup Perspective

Lighting and VBO

Perrytje — Sat, 11 May 2013 06:15:56 -0700

Hi,

I've loaded a couple of cubes into a VBO, and now I'm trying to light them, the problem is however that they act like every cube has it's own light source, instead of having one look.

It almost appears as if the distance to the light is not taken into account at all.

Here's what it looks like at the moment, I don't want these weird changes in colour on the surface:

Can anybody help me?

Voxel Engine built with OpenTK / C#

dimension314 — Wed, 04 Jul 2012 20:24:19 -0700

Hi everyone, I made a blog entry on this site as well, but figured I'd post in here also as I had never even noticed the blogs before today.

I've been reading the OpenTK forum and working with OpenTK for about a year now. Want to thank everyone that has contributed to OpenTK, its so nice being able to develop for OpenGL in Visual Studio/C# where I'm already very comfortable and use everyday at my "day jobs" and not having to learn another language / IDE. Wouldnt have made near as much progress without OpenTK.

Wanted to post a link to the main project I've been working on, which is a voxel engine built in C# and OpenGL utilizing OpenTK. I've seen a lot of voxel engines out there on the web but none very far along using OpenTK.

Please have a look at http://www.voxelgame.com

There you can see screenshots / videos and download a copy of the engine and give it a try. Currently the engine supports the creation of randomly generated worlds, building blocks, breaking blocks, sounds, multiplayer and more. Once in the game, press F1 for a list of commands. You can even try connecting to my server at hornet.voxelgame.com

OpenTK and fonts

lid6j86 — Wed, 04 Jul 2012 00:47:16 -0700

What is the best alternative to FreeType for C#? does OpenTK have anything built into it to help with rendering text?

AltSketch C# Software Vector Graphics Library with native C# implementation of FreeType font rendering library

AltSoftLab — Thu, 09 May 2013 04:50:19 -0700

AltSketch - pure C# CLS compliant 100% managed, without unsafe blocks Software Vector Graphics Library. AltSketch includes AltNETType - pure C# CLS compliant port of wonderful font rendering library Freetype. AltNETType presented as a subsystem of AltSketch in Alt.NETType namespace. AltSketch contains highlevel font realization working with many fontfamilies (system fonts, custom font files). But also FreeType like interface is available throw Alt.NETType namespace of AltSketch library. AltSketch is free for no commercial use.

AltSketch C# Freetype port

AltSoftLab — Thu, 09 May 2013 04:43:21 -0700

We are developers of AltSketch - pure C# CLS compliant 100% managed, without unsafe blocks Software Vector Graphics Library. AltSketch includes AltNETType - native C# implementation of wonderful font rendering library Freetype. AltNETType presented as a subsystem of AltSketch in Alt.NETType namespace.

ReadPixels

ilyazyilmaz — Thu, 25 Apr 2013 11:33:25 -0700

When thiscode run ,

             IntPtr abc=new IntPtr(0);
            GL.ReadPixels(10, 10, 1, 1, PixelFormat.Rgba, PixelType.Float, abc);

windows give this error:
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I looked forum , this problem is occur too much.
How Can I solve this problem???

Problem loading images on Linux

winterhell — Wed, 01 May 2013 00:25:56 -0700

So, My code works on Windows. On Linux it works only for a single image, otherwise throws "Unhandled Exception: System.ArgumentException: A null reference or invalid value was found [GDI+ status: InvalidParameter] at System.Drawing.GDIPlus.CheckStatus (Status status) [0x00000] in :0 " etc
The code that crashes it is

if (!File.Exists(filename)) throw new Exception("File not found") ;
            Bitmap TextureBitmap = new Bitmap(filename);
            int width = TextureBitmap.Width;
            int height = TextureBitmap.Height;  
            System.Drawing.Imaging.BitmapData TextureData =
            TextureBitmap.LockBits(new System.Drawing.Rectangle(0, 0, TextureBitmap.Width, TextureBitmap.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
 
 
            GL.GenTextures(1, out texIndex);
            //tell OpenGL that this is a 2D texture
            GL.BindTexture(TextureTarget.Texture2D, texIndex);
 
            //the following code sets certian parameters for the texture

Black Screen Shot

sYnced — Thu, 25 Apr 2013 03:34:01 -0700

Well OpenTK people, im new here, and im a noobiest c# coder.

I want take screenshot a game (counter strike 1.6), but when i take the screen has black.

Here is my code (i have see here.)

// Creates a 1.0-compatible GraphicsContext with GraphicsMode.Default
        GameWindow window = new GameWindow();
 
        // Creates a 3.0-compatible GraphicsContext with 32bpp color, 24bpp depth
        // 8bpp stencil and 4x anti-aliasing.
        GLControl control = new GLControl(new GraphicsMode(32, 24, 8, 4), 3, 0, 0);
 
        public Bitmap GrabScreenshot()
        {
            if (GraphicsContext.CurrentContext == null)
                throw new GraphicsContextMissingException();
 
            Bitmap bmp = new Bitmap(this.ClientSize.Width, this.ClientSize.Height);
            System.Drawing.Imaging.BitmapData data =
                bmp.LockBits(this.ClientRectangle, System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);

Access Gl texture from OpenCl.Net?

mordrek — Mon, 06 May 2013 13:38:12 -0700

Hi.

Computing with OpenCl.Net works like a charm, but I'd like to alter a texture with it.
Sure I can do the OpenCl computations, upload to mem and then download to Gl texture, but that doesn't seem efficient.

Is there some way I can access Gl texture from OpenCl (or vice versa)?

I can only find examples with Cloo and OpenTK, but not with OpenCl.Net and OpenTK.
Nowhere can I find CreateFromGLBuffer or similar :(

Threading with OpenTK GameWindow

stin8er — Tue, 30 Apr 2013 22:21:02 -0700

Hello Community,

I have been having some problems lately trying to buffer some vertex data.

Well I have been having trouble even generating the Buffers.

The only time when anything like bind buffer works is when the gamewindow is first opened in the default constructor.

The code I use there is:

             public GraphicsEngine(int x, int y, GraphicsMode m, string title, GameWindowFlags gmf) : base(x, y, m, title, gmf)
        {
            //Make full Screen?
            GL.Enable(EnableCap.DepthTest);
            GL.GenBuffers(1, bufferoneHandle);
        }

The exception occuring is: AccessViolationException - Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I have tried to fix it by moving the code around but the exception just occurs on another part of the code eg the enableclientstate or bindbuffer or bufferdata.

I am not sure if I am missing anything obvious!? If any more info is needed please let me know.

The following is the main code I use:

public void DrawArrayBeginMode(List<Vector3d> vector)
        {

Processing window events in a separate thread

Shiny — Wed, 24 Apr 2013 13:46:28 -0700

What is the best way to prevent actions such as window-dragging from blocking the main thread?
I'd like to keep synchronous access to window properties such as location and size.

I have a working solution, but it doesn't seem thread-safe.

My solution consists of two threads:

GUI Thread:

Creates a NativeWindow and registers event handlers to it. The event handlers do nothing more than queue the resulting events.
Calls NativeWindow.ProcessEvents() in a loop. The event handlers queue the results.
Does not interact with NativeWindow in any other way.

Main thread:

Creates the OpenGL context and attaches it to the NativeWindow.
Performs all program logic and rendering, including swapping framebuffers.
Does not directly use NativeWindow's events. Instead, the GUI thread's queued events are used.
Directly accesses NativeWindow's properties such as NativeWindow.Bounds and NativeWindow.WindowInfo.

Wrong Version? Wrong Documentation? Wrong Idea?

Zsar — Mon, 15 Apr 2013 10:24:49 -0700

Environment:

NVIDIA GeForce 310M
Intel Core i3 CPU
Windows 7 Professional SP1 x64
Mono C# compiler version 3.0.8.0 (Mono 3.0.9)
OpenTK 1.0 stable (from here)
Video Driver nv 9.18.13.697

My last C# Project is a couple of years old, so I may be a bit rusty - mayhap I forgot something important, but assuming I did not:

Here is stated for OpenTK version 0.9.x-dev:

the Fiddler wrote:

The game loop is now completely optional. You can inherit from NativeWindow to provide a completely custom game loop, or inherit from GameWindow and override the Run() method.

This appears, however, not to be the case in my version: To be overriden, run must be tagged as virtual or override and it is neither.
... Mayhap this was just bad wording and I am supposed to hide the method? Unfortunately it calls private members of OpenTK.GameWindow (update_watch, render_watch, DispatchUpdateAndRenderFrame) before entering the loop, so I cannot reimplement all the functionality but that.

GL.Enable(EnableCap.PointSmoot) seems not to work for me

alex_konnen — Fri, 19 Apr 2013 04:05:49 -0700

Hello,
I am absolutely new on this list and also relatively new in what concerns OpenTK.
I am trying to render a simple array of 3D points which is not a problem, only that the points always remain rough square, although I apply a
GL.Enable(EnableCap.PointSmoot)
while rendering, like follows:

GL.Enable(EnableCap.PointSmooth);
GL.PointSize(mySize);
GL.Color4(myColor);
 
GL.Begin(BeginMode.Points);
GL.Vertex3(myVertex);
GL.End();

What could be the reason of this behavior? Is there anything I am doing wrongly?
Thanks in advance,
Alex

Selection/Picking

djk — Thu, 17 Jan 2008 05:40:08 -0800

Background:
Over the last 20 years I have been using the Hoops3d graphics system from TechSoft to provide rendering and graphical selection of objects in a large engineering application. My last foray into OpenGl was 15 years ago on an SGI Onyx using the GLUT framework to render a simulation there was no picking required.

I have recently started with a new company that is chartered to create a similar engineering system as open source using the .Net framework. The requirements have lead us to OpenGL and the OpenTK GlControl has risen to the top of the list from the 3-4 open source C# OpenGl controls evaluated.

In the Hoops3d system one would apply a filter to the segment tree (scene graph) to specify what you were going to select, ie whole object, face of a shell, line/edge, or vertex. Every graphical item had a key which could be remapped to a reference to the object that generated it. Thus when you selected an item you accessed the key to get the underlying object to operate on.

Question:

Glu.gluPickMatrix_Similar Command

rathan001 — Mon, 22 Apr 2013 15:13:30 -0700

I am using a mouse picking example by using winforms. What is the similar command in openTK (something like GL.XXXXXXX)

Glu.gluPickMatrix((double) x, (double) (viewport[3] - y), 5.0, 5.0, viewport);

GL.ReadPixels broken?

Inertia — Tue, 06 Oct 2009 08:15:23 -0700

I'm toying with an implementation of the picking technique suggested here.

However it appears that this code will always return 4x zero, although the buffer was previously cleared with 4x 1f.

  // after bind FBO, draw obj, while FBO is bound and readbuffer set to correct color attachment:
  Byte4 Pixel = new Byte4();
  GL.ReadPixels<Byte4>(Mouse.X, FBO_height-Mouse.Y, 1, 1, PixelFormat.Rgba, PixelType.UnsignedByte, ref Pixel);
  uint SelectedTriangle = Pixel.ToUInt32();

this code does prove that there's neither a problem with the FBO nor the attachment:

  // after bind FBO, draw obj, unbind FBO 
  GL.Enable(EnableCap.Texture2D);
  GL.BindTexture(Target, ColorAttachment);
  Byte4[] Tex = new Byte4[FBO_width * FBO_height];
  GL.GetTexImage<Byte4>(Target, 0, PixelFormat.Rgba, PixelType.UnsignedByte, Tex);
  GL.BindTexture(Target, 0);
  GL.Disable(EnableCap.Texture2D);
  SelectedTriangle = Tex[(FBO_height-Mouse.Y)*FBO_width+Mouse.X].ToUInt32();

Transparency Issues with Model and Sprite

redman2k — Fri, 19 Apr 2013 11:21:01 -0700

Hello,

I have recently updated my model/sprite rendering, so items in the back will render before items in the front. I am still running into an issue and I'm not certain how to remedy it. I have attached two pictures that will hopefully help tell my story. In the first picture you can see the tree and sprite are rendered properly, the branch extends over the sprite just fine.

Chapter 0: Learn OpenTK in 15'

Palidan — Mon, 07 Sep 2009 13:54:20 -0700

So, you have downloaded the latest version of OpenTK - what now?

This is a short tutorial that will help you get started with OpenTK in 3 simple steps.

[Step 1: Installation]

Run the installer you downloaded. It will ask where you want OpenTK to be installed. Any folder will do.

[Step 2: Use OpenTK]

Create a new project in your .NET IDE (don't have a .NET IDE? Check out MonoDevelop or Visual Studio Express). Make it of type "Console Application". In the "Solution Explorer" pane, rightclick "References" and select to "Add Reference". In the Browse tab, select OpenTK and click OK.

OpenTK depends on System.Drawing, so you also need to add a reference to System.Drawing.dll. In the "Solution Explorer" pane, rightclick "References" and select to "Add Reference". In the .NET tab, select System.Drawng and click OK.

OpenTK Tutorial

rathan001 — Tue, 16 Apr 2013 18:55:12 -0700

I am new to OpenTK, could anybody share some basic tutorial ? (I plan to develop a 2D CAD application first and then 3D)

Regards,
Pahee