Question

I’m having some GLSL problems. When I just use normal VBO’s without the shaders, everything shows up on screen as expected, and I can move around.

As soon as I link the shader, it’s like it ‘freezes’, draws once, and does not refresh. I checked and the update and render frames are executing as they should be (did a messagebox output check to make sure that it was reaching the code).

I’m thinking it has to be something to do with the matrixes, but I dont know what it is

Here is what I have:

Shader Creation:

private int vertShadHandle, fragShadHandle;
    private int shadProgHandle;

    private void ShaderCreate()
    {
        string vertShadeSource, fragShadeSource, vertcontent,fragcontent;

        vertcontent = System.IO.File.ReadAllText(@"resources/shaders/vertcoordshader.glsl");
        fragcontent = System.IO.File.ReadAllText(@"resources/shaders/fragcoordshader.glsl");


        vertShadeSource = "resources/shaders/vertcoordshader.glsl";
        fragShadeSource = "resources/shaders/fragcoordshader.glsl";


        Console.WriteLine("\nvertex shader path:" + System.IO.File.Exists("/resources/shaders/vertcoordshader.glsl"));
        Console.WriteLine("frag shader path:" + System.IO.File.Exists("/resources/shaders/fragcoordshader.glsl\n"));

        vertShadHandle= GL.CreateShader(ShaderType.VertexShader);  //connect the handles to created shaders
        fragShadHandle = GL.CreateShader(ShaderType.FragmentShader);

        shadProgHandle = GL.CreateProgram();  //create shader program

        GL.ShaderSource(vertShadHandle,vertcontent); //attach file to the shader handle
        GL.ShaderSource(fragShadHandle,fragcontent);

        GL.CompileShader(vertShadHandle); //compile the shaders
        GL.CompileShader(fragShadHandle);

        Console.WriteLine("\n" + GL.GetShaderInfoLog(vertShadHandle) + "\n");
        Console.WriteLine("\n" + GL.GetShaderInfoLog(fragShadHandle) + "\n");

        GL.AttachShader(shadProgHandle, vertShadHandle); //attach the shader to the program created
        GL.AttachShader(shadProgHandle, fragShadHandle);

        //BindAttributes go here (optional)


        GL.BindAttribLocation(shadProgHandle,0,"a_Vertex");
        GL.BindAttribLocation(shadProgHandle, 1, "a_Color");

        GL.UniformMatrix4(GL.GetUniformLocation(shadProgHandle,"MVP"), false, ref MVP);

        GL.LinkProgram(shadProgHandle); //sanity check on the created shader program, links it

        Console.WriteLine("\n"+ GL.GetProgramInfoLog(shadProgHandle) +"\n");

        GL.DeleteShader(vertShadHandle);
        GL.DeleteShader(fragShadHandle);

    }

Update Frame:

 protected override void OnUpdateFrame(FrameEventArgs e)
    {


        const float PIE = 3.141592654f;

        gamePad = XNA.GamePad.GetState(Microsoft.Xna.Framework.PlayerIndex.One);

        camAngle.Y += gamePad.ThumbSticks.Right.X * (float)e.Time * 180;
        camAngle.X += gamePad.ThumbSticks.Right.Y * (float)e.Time * 180;

        Vector2 RadAng = new Vector2();

        RadAng.X = (camAngle.X / 180 * PIE);
        RadAng.Y = (camAngle.Y / 180 * PIE);


        if (gamePad.ThumbSticks.Left.Y > 0)
        {
            camCoord.X -= (float)(Math.Sin(RadAng.Y) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
            camCoord.Z += (float)(Math.Cos(RadAng.Y) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
            camCoord.Y += (float)(Math.Sin(RadAng.X) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
        }
        if (gamePad.ThumbSticks.Left.Y < 0)
        {
            camCoord.X -= (float)(Math.Sin(RadAng.Y) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
            camCoord.Z += (float)(Math.Cos(RadAng.Y) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
            camCoord.Y += (float)(Math.Sin(RadAng.X) * gamePad.ThumbSticks.Left.Y) * (float)(e.Time);
        }
        if (gamePad.ThumbSticks.Left.X > 0)
        {
            camCoord.X -= (float)(Math.Cos(RadAng.Y) * gamePad.ThumbSticks.Left.X) * (float)(e.Time);
            camCoord.Z -= (float)(Math.Sin(RadAng.Y) * gamePad.ThumbSticks.Left.X) * (float)(e.Time);
        }
        if (gamePad.ThumbSticks.Left.X < 0)
        {
            camCoord.X -= (float)(Math.Cos(RadAng.Y) * gamePad.ThumbSticks.Left.X) * (float)(e.Time);
            camCoord.Z -= (float)(Math.Sin(RadAng.Y) * gamePad.ThumbSticks.Left.X) * (float)(e.Time);
        }

        //camCoord.X -= (float)(Math.Sin(RadAng.Y));
        //camCoord.Z += (float)(Math.Cos(RadAng.Y));
        //camCoord.Y += (float)(Math.Sin(RadAng.X));

        if (camAngle.X > 89)
        {
            camAngle.X = 89;
        }
        if (camAngle.X < -89)
        {
            camAngle.X = -89;
        }

        if (camAngle.Y > 360)
        {
            camAngle.Y -= 360;
        }
        else if (camAngle.Y < 0)
        {
            camAngle.Y += 360;
        }

        CameraMatrix();
        MVP = Matrix4.Mult(camMatrix, perspectivematrix);
    }

Camera Function:

public Matrix4 MVP = new Matrix4();
    public Matrix4 camMatrix = new Matrix4();
    private void CameraMatrix()
    {
        camMatrix = Matrix4.Identity;
        camMatrix = Matrix4.CreateRotationX(camAngle.X);
        camMatrix = Matrix4.CreateRotationY(camAngle.Y);
        camMatrix = Matrix4.CreateTranslation(camCoord);
        //GL.Rotate(camAngle.X, 1, 0, 0);
        //GL.Rotate(camAngle.Y, 0, 1, 0);
        //GL.Translate(camCoord);
    }

Render Frame:

protected override void OnRenderFrame(FrameEventArgs e)
    {

        //Qfont display debug info



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


        coordSys.Draw(ref shadProgHandle);

        GL.PushAttrib(AttribMask.ColorBufferBit);


        int qFontLine = 0;
        QFont.Begin();
        InfFont.Print("FPS: " + Math.Round(RenderFrequency, 2), new Vector2(0, 0));
        ++qFontLine;
        InfFont.Print(new String('\n', ++qFontLine) + "X: " + -Math.Round(camCoord.X, 2));
        InfFont.Print(new String('\n', ++qFontLine) + "Y: " + -Math.Round(camCoord.Y, 2));
        InfFont.Print(new String('\n', ++qFontLine) + "Z: " + -Math.Round(camCoord.Z, 2));
        ++qFontLine;
        InfFont.Print(new String('\n', ++qFontLine) + "H-Angle: " + -Math.Round(camAngle.Y, 2));
        InfFont.Print(new String('\n', ++qFontLine) + "V-Angle: " + -Math.Round(camAngle.X, 2));
        ++qFontLine;
        InfFont.Print(new String('\n', ++qFontLine) + "Thumbsticks: ");
        InfFont.Print(new String('\n', ++qFontLine) + "Left.X : " + Math.Round(gamePad.ThumbSticks.Left.X,2));
        InfFont.Print(new String('\n', ++qFontLine) + "Left.Y : " + Math.Round(gamePad.ThumbSticks.Left.Y,2));
        InfFont.Print(new String('\n', ++qFontLine) + "Right.X: " + Math.Round(gamePad.ThumbSticks.Right.X,2));
        InfFont.Print(new String('\n', ++qFontLine) + "Right.X: " + Math.Round(gamePad.ThumbSticks.Right.Y,2));
        QFont.End();

        GL.PopAttrib();

        SwapBuffers();
    }

The Drawing command

GL.UseProgram(ShaderProgramHandle);


 GL.EnableVertexAttribArray(0);
        GL.EnableVertexAttribArray(1);

        GL.BindBuffer(BufferTarget.ArrayBuffer, _VBO[1]);
        GL.VertexAttribPointer(1, 3, VertexAttribPointerType.Float, false, 0, 0);

        GL.BindBuffer(BufferTarget.ArrayBuffer, _VBO[0]);
        GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 0, 0);



        GL.DrawArrays(BeginMode.Lines, 0, 6);


        GL.DisableVertexAttribArray(0);
        GL.DisableVertexAttribArray(1);

and finally, the vertex and frag shaders respectively:

    #version 330

in vec3 a_Vertex;
in vec3 a_Color;

uniform mat4 MVP;

out vec3 color;

void main()
{

    gl_Position = vec4(a_Vertex,1.0);// * MVP;

    color = a_Color;
}

    #version 330

in vec3 color;
out vec4 outColor;

void main()
{
    outColor = vec4(1,1,1,1.0); 
}

Answer 1

I’ve figured it out. I changed the vertex shader to say

gl_Position = gl_ModelViewProjectionMatrix * vec4(a_Vertex,1.0);

which I didn’t know existed