CODEWITHSUNDEEP
c#openglopentkvisual-studio-2015
LAK132
LAK132

Reputation: 193

System Access Violation on GL.DrawArrays

Im getting an Access Violation when ever I run this code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.OpenGL;
using OpenTK.Input;
using System.IO;

namespace OpenTKTutorial1
{
    class Game : GameWindow
    {
        int pgmID;
        int vsID;
        int fsID;

        int attribute_vcol;
        int attribute_vpos;
        int uniform_mview;

        int vbo_position;
        int vbo_color;
        int vbo_mview;

        Vector3[] vertdata;
        Vector3[] coldata;
        Matrix4[] mviewdata;

        void initProgram()
        {
            pgmID = GL.CreateProgram();

            loadShader("vs.glsl", ShaderType.VertexShader, pgmID, out vsID);
            loadShader("fs.glsl", ShaderType.FragmentShader, pgmID, out fsID);

            GL.LinkProgram(pgmID);
            Console.WriteLine(GL.GetProgramInfoLog(pgmID));

            attribute_vpos = GL.GetAttribLocation(pgmID, "vPosition");
            attribute_vcol = GL.GetAttribLocation(pgmID, "vColor");
            uniform_mview = GL.GetUniformLocation(pgmID, "modelview");

            if (attribute_vpos == -1 || attribute_vcol == -1 || uniform_mview == -1)
            {
                Console.WriteLine("Error binding attirbutes");
            }

            GL.GenBuffers(1, out vbo_position);
            GL.GenBuffers(1, out vbo_color);
            GL.GenBuffers(1, out vbo_mview);
        }

        void loadShader(String filename, ShaderType type, int program, out int address)
        {
            address = GL.CreateShader(type);
            using (StreamReader sr = new StreamReader(filename))
            {
                GL.ShaderSource(address, sr.ReadToEnd());
            }
            GL.CompileShader(address);
            GL.AttachShader(program, address);
            Console.WriteLine(GL.GetShaderInfoLog(address));
        }

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            initProgram();

            vertdata = new Vector3[]{
                new Vector3(-0.8f, -0.8f, 0f),
                new Vector3(0.8f, -0.8f, 0f),
                new Vector3(0f, 0.8f, 0f)};

            coldata = new Vector3[]{
                new Vector3(1f, 0f, 0f),
                new Vector3(0f, 0f, 1f),
                new Vector3(0f, 1f, 0f)};


            mviewdata = new Matrix4[]{
                Matrix4.Identity};

            Title = "Title";
            GL.ClearColor(Color.CornflowerBlue);
            GL.PointSize(5f);
        }

        protected override void OnRenderFrame(FrameEventArgs e)
        {
            base.OnRenderFrame(e);

            GL.Viewport(0, 0, Width, Height);
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
            GL.Enable(EnableCap.DepthTest);

            GL.EnableVertexAttribArray(attribute_vpos);
            GL.EnableVertexAttribArray(attribute_vcol);

            GL.DrawArrays(PrimitiveType.Triangles, 0, 3);

            GL.DisableVertexAttribArray(attribute_vpos);
            GL.DisableVertexAttribArray(attribute_vcol);

            GL.Flush();

            //Everything before this
            SwapBuffers();
        }

        protected override void OnUpdateFrame(FrameEventArgs e)
        {
            base.OnUpdateFrame(e);

            GL.BindBuffer(BufferTarget.ArrayBuffer, vbo_position);
            GL.BufferData<Vector3>(BufferTarget.ArrayBuffer, (IntPtr)(vertdata.Length * Vector3.SizeInBytes), vertdata, BufferUsageHint.StaticDraw);
            GL.VertexAttribPointer(attribute_vpos, 3, VertexAttribPointerType.Float, false, 0, 0);

            GL.BindBuffer(BufferTarget.ArrayBuffer, vbo_color);
            GL.BufferData<Vector3>(BufferTarget.ArrayBuffer, (IntPtr)(coldata.Length * Vector3.SizeInBytes), coldata, BufferUsageHint.StaticDraw);
            GL.VertexAttribPointer(attribute_vcol, 3, VertexAttribPointerType.Float, true, 0, 0);

            GL.UniformMatrix4(uniform_mview, false, ref mviewdata[0]);

            GL.UseProgram(pgmID);

            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
        }
    }
}

It makes it to rendering the background then crashes.

I'm quite new to OpenTK and OpenGL so I'm not 100% sure what the problem is.

The error is thrown at 

GL.DrawArrays(PrimitiveType.Triangles, 0, 3);

Upvotes: 1

Views: 1465

Answers (1)

Gigo
Gigo

Reputation: 3264

There are a few minor issues with your code, but it works for me without changes.

Regardless, I have made a few changes and added commentary to explain why, maybe something fixes it for you. If not please post your shaders and more detail on the exact exception, if there is any.

using System;
using System.Drawing;
using System.IO;
using OpenTK;
using OpenTK.Graphics.OpenGL;

namespace OpenTKTutorial1
{
    public class Game
        : GameWindow
    {
        int pgmID;
        int vsID;
        int fsID;

        int attribute_vcol;
        int attribute_vpos;
        int uniform_mview;

        int vbo_position;
        int vbo_color;
        int vbo_mview;

        Vector3[] vertdata;
        Vector3[] coldata;
        Matrix4[] mviewdata;

        public Game()
        {
            // better use the events instead of overriding the inherited methods
            // at least thats what the documentation on Update- and RenderFrame says
            Load += OnLoad;
            UpdateFrame += OnUpdateFrame;
            RenderFrame += OnRenderFrame;
        }

        void InitProgram()
        {
            pgmID = GL.CreateProgram();

            LoadShader("vs.glsl", ShaderType.VertexShader, pgmID, out vsID);
            LoadShader("fs.glsl", ShaderType.FragmentShader, pgmID, out fsID);

            GL.LinkProgram(pgmID);
            Console.WriteLine(GL.GetProgramInfoLog(pgmID));

            attribute_vpos = GL.GetAttribLocation(pgmID, "vPosition");
            attribute_vcol = GL.GetAttribLocation(pgmID, "vColor");
            uniform_mview = GL.GetUniformLocation(pgmID, "modelview");

            if (attribute_vpos == -1 || attribute_vcol == -1 || uniform_mview == -1)
            {
                Console.WriteLine("Error binding attributes");
            }

            GL.GenBuffers(1, out vbo_position);
            GL.GenBuffers(1, out vbo_color);

            // what is this buffer for?
            //GL.GenBuffers(1, out vbo_mview);
        }

        void LoadShader(String filename, ShaderType type, int program, out int address)
        {
            address = GL.CreateShader(type);
            using (StreamReader sr = new StreamReader(filename))
            {
                GL.ShaderSource(address, sr.ReadToEnd());
            }
            GL.CompileShader(address);
            GL.AttachShader(program, address);
            Console.WriteLine(GL.GetShaderInfoLog(address));
        }

        protected void OnLoad(object sender, EventArgs eventArgs)
        {
            InitProgram();

            vertdata = new Vector3[]{
                new Vector3(-0.8f, -0.8f, 0f),
                new Vector3(0.8f, -0.8f, 0f),
                new Vector3(0f, 0.8f, 0f)};

            coldata = new Vector3[]{
                new Vector3(1f, 0f, 0f),
                new Vector3(0f, 0f, 1f),
                new Vector3(0f, 1f, 0f)};


            mviewdata = new Matrix4[]{
                Matrix4.Identity};

            Title = "Title";
            GL.ClearColor(Color.CornflowerBlue);
            GL.PointSize(5f);
        }

        protected void OnRenderFrame(object sender, FrameEventArgs frameEventArgs)
        {
            // if you only have one viewport you can safely move this to the OnResize event
            GL.Viewport(0, 0, Width, Height);

            // if the state never changes move it to OnLoad
            GL.Enable(EnableCap.DepthTest);

            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);

            GL.EnableVertexAttribArray(attribute_vpos);
            GL.EnableVertexAttribArray(attribute_vcol);

            // always make sure the program is enabled ..
            GL.UseProgram(pgmID);
            // .. before you set any uniforms 
            GL.UniformMatrix4(uniform_mview, false, ref mviewdata[0]);
            // .. or draw anything
            GL.DrawArrays(PrimitiveType.Triangles, 0, 3);

            GL.DisableVertexAttribArray(attribute_vpos);
            GL.DisableVertexAttribArray(attribute_vcol);

            // do not call glFlush unless you have a very good reason to
            // it can result in significant slow downs
            //GL.Flush();

            SwapBuffers();
        }

        protected void OnUpdateFrame(object sender, FrameEventArgs frameEventArgs)
        {
            // your vertex and color data never changes, thus everything you do here
            // could be moved to OnLoad instead of having it repeated all the time
            GL.BindBuffer(BufferTarget.ArrayBuffer, vbo_position);
            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(vertdata.Length * Vector3.SizeInBytes), vertdata, BufferUsageHint.StaticDraw);
            GL.VertexAttribPointer(attribute_vpos, 3, VertexAttribPointerType.Float, false, 0, 0);

            GL.BindBuffer(BufferTarget.ArrayBuffer, vbo_color);
            GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(coldata.Length * Vector3.SizeInBytes), coldata, BufferUsageHint.StaticDraw);
            GL.VertexAttribPointer(attribute_vcol, 3, VertexAttribPointerType.Float, true, 0, 0);

            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
        }
    }
}

Upvotes: 2

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