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POSDL OpenGL Rendering Issue
 

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  1. POSDL OpenGL Rendering Issue
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    <p>I am just learning how to use SDL and openGL. I've been through the tutorials over at SDLTutorials.com. I am now trying to take things further and create a loading screen for an application; an oop menu system. </p> <p>I am starting off real simple to test things out. I have the main backdrop of the window done via a texture class. The two relevant functions are defined here:</p> <pre><code>void Texture::Bind() { glBindTexture(GL_TEXTURE_2D, TextureID); } void Texture::RenderQuad(int X, int Y, int Width, int Height) { Bind(); glBegin(GL_QUADS); glTexCoord2f(0, 0); glVertex3f(X, Y, 0); glTexCoord2f(1, 0); glVertex3f(X + Width, Y, 0); glTexCoord2f(1, 1); glVertex3f(X + Width, Y + Height, 0); glTexCoord2f(0, 1); glVertex3f(X, Y + Height, 0); glEnd(); } </code></pre> <p>I also have created a menu class that will basically be the parent of any menu created in the system and classes to be developed would be like a click button or an edit box. So far, the only relevent function in class Menu is:</p> <pre><code>void Menu::OnRender() { if( Visible ) { if(MenuTexture == NULL) { glColor4f(1.,G,B,A); glBegin(GL_QUADS); glVertex2d(X, Y); glVertex2d(X+Width,Y); glVertex2d(X+Width,Y+Height); glVertex2d(X,Y+Height); glEnd(); }else{ MenuTexture-&gt;RenderQuad(X,Y,Width,Height); } } } </code></pre> <p>Finally, my application has created one texture that it binds to the whole window. i.e. the backround. </p> <pre><code>void App::OnRender() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); MainScreen.RenderQuad(0,0,winWidth,winHeight); //Texture Object with bkg.jpg MainMenu.OnRender(); //Menu object to be 150x300 and all black SDL_GL_SwapBuffers(); } </code></pre> <p>I then create a menu item and try to draw it over the backdrop. If I leave the initialized colors black, the entire screen turns black almost instantly: I have one frame probably the first cycle through where the menu is drawn, the black square is placed on the window, and then it turns black.. If I have 1.0 for the Red, then the entire picture has like some sort of red filter placed on it and the menu box draws an opaque red square. </p> <p>I've been through several examples of how rendering but I must be missing something. Essentially, if we put it all in line of whats being done, I bind the texture to a surface, define the coordinates of the surface and texture binding. Then I render a quad. I've put the color call in my menu inside the glBegin(), defining the color at all 4 vertices. </p> <p>Thanks to my chosen answer: This solved the issue. However, it didn't render the Menu object with the correct color until I returned it to modulate. Not sure, I'll be playing around with it and reading up on this to learn about it. Thank you! </p> <p>[SOVLED] Changes only made to <code>App::OnRender()</code>:</p> <pre><code>glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); MainScreen.RenderQuad(0,0,winWidth,winHeight); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); MainMenu.OnRender(); </code></pre>
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