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Ortho mode

Started by Ilmater Nov 18, 2004 at 8:44 PM 7 replies 1.6k views

Original Post

Nov 18, 2004 at 8:44 PM

Does anyone have any idea why this code wouldn't work? int DrawGLScene(GLvoid) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glDisable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); glPushMatrix(); glLoadIdentity(); glOrtho(0,800,0,600,0,1); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glBindTexture(GL_TEXTURE_2D, g_Texture[0]); glBegin(GL_QUADS); glTexCoord2f(0.0f, 1.0f); glVertex2f(0, 0); glTexCoord2f(0.0f, 0.0f); glVertex2f(0, 600); glTexCoord2f(1.0f, 0.0f); glVertex2f(800, 600); glTexCoord2f(1.0f, 1.0f); glVertex2f(800, 0); glEnd(); glEnable(GL_DEPTH_TEST); glMatrixMode( GL_PROJECTION ); glPopMatrix(); glMatrixMode( GL_MODELVIEW ); return TRUE; } I am trying to take a texture, and put it across the entire screen in ortho mode.

Raduprv

Nov 18, 2004 at 9:41 PM

I didn't look at what the code does, but did you enable GL_TEXTURE_2D prior to calling that function?

Kalidor

Nov 18, 2004 at 10:27 PM

Do you have back-face culling enabled? It looks to me like you are sending the coordinates in clockwise.

_the_phantom_

Nov 18, 2004 at 10:49 PM

Nope, those verts are going in CCW, same order I've got mine on my own 2D quad drawing code, ditto with the texture coords

- As Raduprv says, texturing definately enabled and bound?
- I assume you do swap the buffers somewhere? [smile]

Ilmater

Nov 19, 2004 at 12:45 AM

phantom: yes to both

smitty1276

Nov 19, 2004 at 12:49 AM

Are you sure that your texture is loading correctly? What is it doing exactly?

overflowed_

Nov 19, 2004 at 1:06 AM

I just ran that function w/o the texture code and it works fine. The problem lies with the texture.

Ilmater

Nov 19, 2004 at 2:27 AM

D'oh! I just found out what was wrong.

I was trying to load a texture that wasn't a power of 2 >.<

Got it working now. Thanks for the help

Kalidor

Nov 19, 2004 at 4:22 PM

Okay, now I'm confused. How is that clockwise?

glOrtho(0,800,0,600,0,1); sets up an ortho mode with (0,0) at the bottom-left and (800,600) at the top-right. Right?

glVertex2f(0, 0);
glVertex2f(0, 600);
glVertex2f(800, 600);
glVertex2f(800, 0);

And this would be bottom-left, top-left, top-right, bottom-right, correct?

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