Rendering A Fullscreen quad using an orthographic viewport.

Graphics and GPU Programming Programming

Started by Code-R October 21, 2005 06:02 AM

10 comments, last by Code-R 18 years, 5 months ago

136

Author

October 21, 2005 06:02 AM

After rendering my scene to a texture using FBOs, I want to setup a fullscreen quad that I overlay the image over. the thing is, I don't see anything except when I translate with some -Z value. what would be causing that? code:


void FinalizeScene()
{
      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
	glLoadIdentity();
	glTranslatef(0,0,-1);
	glDepthFunc(GL_ALWAYS);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glClientActiveTextureARB(GL_TEXTURE0);
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, FrameTexture);
	glGenerateMipmapEXT(GL_TEXTURE_2D);
	glDisable(GL_LIGHTING);
	glColor4f(1,1,1,1);
	glOrtho(0, ViewportWidth, 0, ViewportHeight, -1, 1);
	glBegin(GL_QUADS);
	glTexCoord2f(0,0);
	glVertex2f(0,0);
	glTexCoord2f(0,1);
	glVertex2f(0,ViewportWidth);
	glTexCoord2f(1,1);
	glVertex2f(ViewportHeight, ViewportWidth);
	glTexCoord2f(1,0);
	glVertex2f(ViewportHeight,0);
	glEnd();
	SwapBuffers(hDC);
	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FrameBufferObject);
}

James Trotter

432

October 21, 2005 06:23 AM

void FinalizeScene(){      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);	glLoadIdentity();	glTranslatef(0,0,-1); <-- Is  that really supposed to be there?	glDepthFunc(GL_ALWAYS);	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	glClientActiveTextureARB(GL_TEXTURE0);	glEnable(GL_TEXTURE_2D);	glBindTexture(GL_TEXTURE_2D, FrameTexture);	glGenerateMipmapEXT(GL_TEXTURE_2D);	glDisable(GL_LIGHTING);	glColor4f(1,1,1,1);	glMatrixMode(GL_PROJECTION); <-- Insert this line	glLoadIdentity(); <-- And this one	glOrtho(0, ViewportWidth, 0, ViewportHeight, -1, 1);	glMatrixMode(GL_MODELVIEW);	glBegin(GL_QUADS);	glTexCoord2f(0,0);	glVertex2f(0,0);	glTexCoord2f(0,1);	glVertex2f(0,ViewportWidth);	glTexCoord2f(1,1);	glVertex2f(ViewportHeight, ViewportWidth);	glTexCoord2f(1,0);	glVertex2f(ViewportHeight,0);	glEnd();	SwapBuffers(hDC);	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FrameBufferObject);}

Don't know if this is the correct fix... You might try to use gluOrtho2D instead of glOrtho.

Edit: And another thing. Instead of setting the depth function to GL_ALWAYS, you might as well disable depth testing: glDisable(GL_DEPTH_TEST);
Hope this helps.

zedzeek

529

October 21, 2005 02:05 PM

the easiest method for a fullscreen quad is
set both modelview + project to the identity matrix
and draw a quad of coordinates (-1,-1) -> (1,1)

Captain Courgette, eat more veg

Code-R

136

Author

October 21, 2005 02:14 PM

now the code for fianlizeScene is:

	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);	glLoadIdentity();	//glTranslatef(0,0,-1);	glDisable(GL_DEPTH_TEST);	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	glClientActiveTextureARB(GL_TEXTURE0);	glEnable(GL_TEXTURE_2D);	glBindTexture(GL_TEXTURE_2D, FrameTexture);	glGenerateMipmapEXT(GL_TEXTURE_2D);	glDisable(GL_LIGHTING);	glColor4f(1,1,1,1);	glOrtho(0, ix_FrameWidth, 0, ix_FrameHeight, 0, 1);	//gluOrtho2D(0,ix_FrameWidth, 0, ix_FrameHeight); // not working.	glBegin(GL_QUADS);	glTexCoord2f(0,0);	glVertex2f(0,0);	glTexCoord2f(0,1);	glVertex2f(0,ix_FrameWidth);	glTexCoord2f(1,1);	glVertex2f(ix_FrameHeight,ix_FrameWidth);	glTexCoord2f(1,0);	glVertex2f(ix_FrameHeight,0);	glEnd();	SwapBuffers(hDC);	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FrameBufferObject);

I can see the textured quad, but it's unaligned with the screen. any ideas?

Daaark

3,556

October 21, 2005 02:21 PM

I just set my viewport to ortho and draw a quad as if It was a2d screen with Depth testing turned off.

    glOrtho(0, nWidth, 0, nHeight, -1, 1);            glBegin(GL_QUADS);        glTexCoord2f(0.0f,1.0f);        glVertex2i(0,nHeight-1);        glTexCoord2f(0.0f,0.0f);        glVertex2i(0,0);        glTexCoord2f(1.0f,0.0f);        glVertex2i(nWidth-1,0);        glTexCoord2f(1.0f,1.0f);        glVertex2i(nWidth-1,nHeight-1);    glEnd();

Whya re you making mipmaps of your frame texture? Seems you'll only ever need 1 of them? Am I missing something? You seem to be doing a lot of work there for little effect.

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blueshogun96

2,267

October 21, 2005 03:07 PM

Quote:Whya re you making mipmaps of your frame texture?

It is a good idea to use a mipmapped texture in OpenGL if his texture widh and height are not powers of two. If this is the case, than using a different texture filtering method would cause a MAJOR slowdown in his application.

But here's my reccomendation. Click the link on my sig and try using that method. But the point (0,0) is in the bottom left hand corner so you will have to do some minor calculations to move the (0,0) coordinate back to the top.

Kalidor

1,087

October 21, 2005 03:44 PM

Quote:Original post by Code-R
now the code for fianlizeScene is:
*** Source Snippet Removed ***
I can see the textured quad, but it's unaligned with the screen. any ideas?

You still aren't switching to the projection matrix before you call glOrtho (at least not in what you posted).

Quote:Original post by James Trotter

	glMatrixMode(GL_PROJECTION); <-- Insert this line	glLoadIdentity(); <-- And this one	glOrtho(0, ViewportWidth, 0, ViewportHeight, -1, 1);

And yeah, there's no need for mipmaps if the texture will always be the same size on screen.

EDIT: Just a note, gluOrtho2D is the same as glOrtho with the near and far parameters set to -1 and 1, respectively.

Code-R

136

Author

October 21, 2005 07:39 PM

ok, so now it's

glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	glOrtho(0, ix_FrameWidth, 0, ix_FrameHeight, 0, 1);	//glTranslatef(0,0,-1);	glDisable(GL_DEPTH_TEST);	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	glClientActiveTextureARB(GL_TEXTURE0);	glEnable(GL_TEXTURE_2D);	glBindTexture(GL_TEXTURE_2D, FrameTexture);	glGenerateMipmapEXT(GL_TEXTURE_2D);	glDisable(GL_LIGHTING);	glColor4f(1,1,1,1);	//gluOrtho2D(0,ix_FrameWidth, 0, ix_FrameHeight);	glBegin(GL_QUADS);	glTexCoord2f(0,0);	glVertex2f(0,0);	glTexCoord2f(0,1);	glVertex2f(0,ix_FrameWidth);	glTexCoord2f(1,1);	glVertex2f(ix_FrameHeight,ix_FrameWidth);	glTexCoord2f(1,0);	glVertex2f(ix_FrameHeight,0);	glEnd();	SwapBuffers(hDC);	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, FrameBufferObject);

The results are much better, but they're still not perfect. the quad doesn't fill the screen, it leaves a border on the right/bottom. any ideas?

Shanjaq

151

October 21, 2005 07:57 PM

Here's what I do:

// Push back and cache the current state of depth testing and lighting// and then disable them.glPushAttrib( GL_TEXTURE_BIT | GL_DEPTH_TEST | GL_LIGHTING );glDisable( GL_DEPTH_TEST );glDisable( GL_LIGHTING );// Push back the current matrices and go orthographic for background rendering.glMatrixMode( GL_PROJECTION );glPushMatrix();glLoadIdentity();glOrtho( 0, 1024, 768, 0, -1, 1 );  //or whatever size you wantglMatrixMode( GL_MODELVIEW );glPushMatrix();glLoadIdentity();//build the backgroundglBindTexture(GL_TEXTURE_2D, Texture);		// Select Our TextureglBegin(GL_QUADS);				// Draw The Quad	glColor3f( 1.0, 1.0, 1.0 ); 	glTexCoord2f(0.0f, 0.0f); glVertex3f(0.0f, float(nWindowHeight), 0.0f);		// Bottom Left	glTexCoord2f(1.0f, 0.0f); glVertex3f( float(nWindowWidth), float(nWindowHeight), 0.0f);				// Bottom Right	glTexCoord2f(1.0f, 1.0f); glVertex3f( float(nWindowWidth), 0.0f, 0.0f);				// Top Right	glTexCoord2f(0.0f, 1.0f); glVertex3f(0.0f, 0.0f, 0.0f);				// Top LeftglEnd();										// Done Drawing The Quad// Pop everything back to what ever it was set to before we started glMatrixMode( GL_PROJECTION );glPopMatrix();glMatrixMode( GL_MODELVIEW );glPopMatrix();glPopAttrib();

Code-R

136

Author

October 22, 2005 08:26 AM

Quote:Original post by Shanjaq
Here's what I do:

*** Source Snippet Removed ***

THANK YOU! IT WORKED!

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Rendering A Fullscreen quad using an orthographic viewport.

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Rendering A Fullscreen quad using an orthographic viewport.

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