Question

Edit: Okay, this code still doesn’t allow me to use two different textures in the program. It acts like it should work, but when I tell it to use the first texture, it’s the same as the second texture, which is the last texture that’s loaded.

        private int[] iTextures = new int[3];

        public void main()
        {
            Initialize();
            LoadContent();

            float Time = 0.0F;

            // Start game loop
            while (App.IsOpened())
            {
                // Process events
                App.DispatchEvents();

                // Clear the window
                App.Clear();

                App.Draw(Background);

                Gl.glClear(Gl.GL_DEPTH_BUFFER_BIT);

                // Transformations
                Time += App.GetFrameTime();
                Gl.glMatrixMode(Gl.GL_MODELVIEW);
                Gl.glLoadIdentity();
                Gl.glTranslatef(0.0F, 0.0F, -200.0F);


                Gl.glPushMatrix();

                Gl.glScalef(10.0f, 50.0f, 10.0f);
                DrawCube(50.0f, 50.0f, 50.0f, 0);

                Gl.glPopMatrix();

                //Gl.glRotatef(Time * 50, 1.0F, 0.0F, 0.0F);
                //Gl.glRotatef(Time * 30, 0.0F, 1.0F, 0.0F);
                //Gl.glRotatef(Time * 90, 0.0F, 0.0F, 1.0F);


                /*Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, -50.0F, -50.0F);
                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, -50.0F, -50.0F);

                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, -50.0F, 50.0F);
                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, 50.0F, 50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, 50.0F, 50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, -50.0F, 50.0F);

                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, -50.0F, -50.0F);
                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(-50.0F, 50.0F, 50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(-50.0F, -50.0F, 50.0F);

                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(50.0F, -50.0F, -50.0F);
                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, 50.0F, 50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, -50.0F, 50.0F);

                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, -50.0F, 50.0F);
                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, -50.0F, -50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, -50.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, -50.0F, 50.0F);

                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, 50.0F, 50.0F);
                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, 50.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, 50.0F, 50.0F);


                Gl.glVertex3f(50.0f, 50.0f, 50.0f);
                Gl.glVertex3f(50.0f, 0.0f, 50.0f);
                Gl.glVertex3f(0.0f, 0.0f, 50.0f);
                Gl.glVertex3f(0.0f, 50.0f, 50.0f);

                Gl.glTexCoord2f(0, 1); Gl.glVertex3f(-50.0F, 10.0F, 50.0F);
                Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-50.0F, 10.0F, -50.0F);
                Gl.glTexCoord2f(1, 0); Gl.glVertex3f(50.0F, 10.0F, -50.0F);
                Gl.glTexCoord2f(1, 1); Gl.glVertex3f(50.0F, 10.0F, 50.0F);

                Gl.glEnd();*/



                Draw();

                // Finally, display the rendered frame on screen
                App.Display();

            }
            // Don't forget to destroy our texture
            int tex = 0;
            Gl.glDeleteTextures(1, ref tex);
        }

        public void Initialize()
        {
            // Create main window

            App.PreserveOpenGLStates(true);

            // Setup event handlers
            App.Closed += new EventHandler(OnClosed);
            App.KeyPressed += new EventHandler<KeyEventArgs>(OnKeyPressed);
            App.Resized += new EventHandler<SizeEventArgs>(OnResized);
        }

        private void LoadContent()
        {
            BackgroundImage = new Image("background.jpg");
            Background = new Sprite(BackgroundImage);

            Text = new String2D("This is a cube");
            Text.Position = new Vector2(0, 0);
            Text.Color = Color.Black;

            // Enable Z-buffer read and write
            Gl.glEnable(Gl.GL_DEPTH_TEST);
            Gl.glDepthMask(Gl.GL_TRUE);
            Gl.glClearDepth(1.0F);

            // Setup a perspective projection

            Gl.glMatrixMode(Gl.GL_PROJECTION);
            Gl.glLoadIdentity();
            Glu.gluPerspective(90.0F, 1.0F, 1.0F, 500.0F); // I assume this is setting up the camera

            LoadTexture(new Image("texture.jpg"), 0);

            LoadTexture(new Image("Otexture.jpg"), 1);


        }

        private void Draw()
        {
            App.Draw(Text);
        }

        private void LoadTexture(Image Texture, int texNum)
        {

            using (Image TempImage = Texture)
            {

                Gl.glGenTextures(1, out iTextures[texNum]); // Texture name, which is a number

                Gl.glBindTexture(Gl.GL_TEXTURE_2D, iTextures[texNum]); // Start using the texture


                Console.WriteLine(texNum + "");
                // Texture options and filters and stuff
                Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MAG_FILTER, Gl.GL_LINEAR);
                Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MIN_FILTER, Gl.GL_LINEAR_MIPMAP_LINEAR);

                Glu.gluBuild2DMipmaps(Gl.GL_TEXTURE_2D, Gl.GL_RGBA, (int)TempImage.Width, (int)TempImage.Height, Gl.GL_RGBA, Gl.GL_UNSIGNED_BYTE, TempImage.Pixels);
                //Gl.glTexImage2D(Gl.GL_TEXTURE_2D, 0, Gl.GL_RGBA, (int)TempImage.Width, (int)TempImage.Height, 0, Gl.GL_RGBA, Gl.GL_UNSIGNED_BYTE, TempImage.Pixels);

            }
            Gl.glEnable(Gl.GL_TEXTURE_2D);
        }
        private void UseTexture(int iTexture)
        {


            // Bind our texture for use
            //Gl.glEnable(Gl.GL_TEXTURE_2D); // Start using the 2D texture
            Gl.glBindTexture(Gl.GL_TEXTURE_2D, iTexture); // Bind our texture for current use
            Gl.glColor4f(1.0F, 1.0F, 1.0F, 1.0F); // Set color to..white, I think.
        }



        void DrawCube(float xPos, float yPos, float zPos, int texture)
        {

            Gl.glPushMatrix();

            //UseTexture(1);
            Gl.glBegin(Gl.GL_QUADS);
            UseTexture(iTextures[0]);
            //Gl.glEnable(Gl.GL_TEXTURE_2D);



            /*      This is the top face*/
            Gl.glVertex3f(0.0f, 0.0f, 0.0f);
            Gl.glVertex3f(0.0f, 0.0f, -1.0f);
            Gl.glVertex3f(-1.0f, 0.0f, -1.0f);
            Gl.glVertex3f(-1.0f, 0.0f, 0.0f);

            /*      This is the front face*/
            Gl.glTexCoord2f(0, 1); Gl.glVertex3f(0.0f, 0.0f, 0.0f);
            Gl.glTexCoord2f(0, 0); Gl.glVertex3f(-1.0f, 0.0f, 0.0f);
            Gl.glTexCoord2f(1, 0); Gl.glVertex3f(-1.0f, -1.0f, 0.0f);
            Gl.glTexCoord2f(1, 1); Gl.glVertex3f(0.0f, -1.0f, 0.0f);

            /*      This is the right face*/
            Gl.glVertex3f(0.0f, 0.0f, 0.0f);
            Gl.glVertex3f(0.0f, -1.0f, 0.0f);
            Gl.glVertex3f(0.0f, -1.0f, -1.0f);
            Gl.glVertex3f(0.0f, 0.0f, -1.0f);

            /*      This is the left face*/
            Gl.glVertex3f(-1.0f, 0.0f, 0.0f);
            Gl.glVertex3f(-1.0f, 0.0f, -1.0f);
            Gl.glVertex3f(-1.0f, -1.0f, -1.0f);
            Gl.glVertex3f(-1.0f, -1.0f, 0.0f);

            /*      This is the bottom face*/
            Gl.glVertex3f(0.0f, 0.0f, 0.0f);
            Gl.glVertex3f(0.0f, -1.0f, -1.0f);
            Gl.glVertex3f(-1.0f, -1.0f, -1.0f);
            Gl.glVertex3f(-1.0f, -1.0f, 0.0f);

            /*      This is the back face*/
            Gl.glVertex3f(0.0f, 0.0f, 0.0f);
            Gl.glVertex3f(-1.0f, 0.0f, -1.0f);
            Gl.glVertex3f(-1.0f, -1.0f, -1.0f);
            Gl.glVertex3f(0.0f, -1.0f, -1.0f);

            Gl.glEnd();
            Gl.glPopMatrix();
        }

Any help would be awesome.

Answer 1

You’re not talking about multitexturing; you’re talking about using multiple textures in the same application.

Well, I see several problems.

Gl.glGenTextures(2, out iTexture); // Texture name, which is a number

I admit that I’m not 100% familiar with C#’s syntax, so I’m assuming that the out works rather like passing a pointer in C/C++. So you expect glGenTextures to write the texture object number to iTexture.

There are two problems here. First, iTexture is a single integer. But you told glGenTextures that you were generating two textures in this function call, not one. That would require passing an array of integers for glGenTextures to write into. So you’re risking trashing the… stack? I have no idea how you’re marshalling these calls to C++, but however you’re doing it, glGenTextures is likely writing over random memory. You were lucky not to get a crash.

Each call to LoadTexture is supposed to create a single OpenGL texture object. Therefore, you should not be trying to create two from a single LoadTexture call.

The other problem is that iTexture is not returned from your LoadTexture function. You don’t store it anywhere. Indeed, when you call LoadTexture, you don’t even give it an output variable; you give it a number literal. Again, I’m not a C# expert, but I’m pretty sure you would need some special syntax to use an argument as a function output, particularly for a basic type like int.

Your LoadTexture function should return the OpenGL texture names (or store them somewhere), and the matching UseTexture calls should get those particular names from them.

---

New code problems:

// Don't forget to destroy our texture
int tex = 0;
Gl.glDeleteTextures(1, ref tex);

You cannot delete texture 0. That’s generally why people don’t use texture 0 to store actual textures in; it is generally treated as a “texture that doesn’t exist”, like NULL.

As to your actual drawing code:

Gl.glBegin(Gl.GL_QUADS);
UseTexture(iTextures[0]);

You cannot call glBindTexture (or most OpenGL functions) between glBegin/glEnd calls. UseTexture should be called before beginning the quad. Also, UseTexture should enable GL_TEXTURE_2D. I know you use it elsewhere, but it’s best to put commands where they actually matter. And you have to disable GL_TEXTURE_2D if you want to do untextured rendering.

Also, what do you expect to happen when you only give one quad texture coordinates? What do you expect the other quads to look like? Because if you think that those quads will be untextures, you’re wrong.