Irrlicht Engine

Posted: **Fri Sep 07, 2007 3:58 pm**

Hello everyone,

I am trying to implement quad buffered stereo for my project but I am having a tough time in figuring out the sections of the source which actually render using OpenGL. I need to make changes to support writing to back buffers.

Thanks in advance.

Posted: **Fri Sep 07, 2007 6:47 pm**

I have looked at COpenGLdriver.h and .cpp but I am unable to figure out how control flows from beginscene().

Posted: **Fri Sep 07, 2007 8:25 pm**

You will find severl things in CNullDriver, which is the base class. Also the SceneManager is a vital part of the render pipeline.
What's the necessary setup for your render project? I had only tried shutter glasses which were using the stereo caps of the NVidia driver.

Posted: **Sat Sep 08, 2007 1:40 am**

The code below is for implementing active stereo (quad buffered) in an OpenGL application. I need to figure out how I can implement this in Irrlicht.
I will be able to change the camera views but how do I fiddle with drawing to different buffers?
Any other thoughts on implementing the code will also be useful.
Thanks again.

Code: Select all

 Thanks to Paul Bourke.
void HandleDisplay(void)
{
   XYZ r;
   double ratio,radians,wd2,ndfl;
   double left,right,top,bottom;

 
      camera.near = camera.focallength / 10;
 

   /* Misc stuff needed for the frustum */
   ratio   = camera.screenwidth / (double)camera.screenheight;
   if (camera.stereo == DUALSTEREO)
      ratio /= 2;
   radians = DTOR * camera.aperture / 2;
   wd2     = camera.near * tan(radians);
   ndfl    = camera.near / camera.focallength;
   top     =   wd2;
   bottom  = - wd2;

   /* Determine the right eye vector */
   CROSSPROD(camera.vd,camera.vu,r);
   Normalise(&r);
   r.x *= camera.eyesep / 2.0;
   r.y *= camera.eyesep / 2.0;
   r.z *= camera.eyesep / 2.0;

   if (camera.stereo == ACTIVESTEREO || camera.stereo == DUALSTEREO) {

      if (camera.stereo == DUALSTEREO) {
         glDrawBuffer(GL_BACK);
         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      }

      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      left  = - ratio * wd2 - 0.5 * camera.eyesep * ndfl;
      right =   ratio * wd2 - 0.5 * camera.eyesep * ndfl;
      glFrustum(left,right,bottom,top,camera.near,camera.far);
      if (camera.stereo == DUALSTEREO)
         glViewport(camera.screenwidth/2,0,camera.screenwidth/2,camera.screenheight);
      else
         glViewport(0,0,camera.screenwidth,camera.screenheight);
      glMatrixMode(GL_MODELVIEW);
      glDrawBuffer(GL_BACK_RIGHT);
      if (camera.stereo == ACTIVESTEREO)
         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glLoadIdentity();
      gluLookAt(camera.vp.x + r.x,camera.vp.y + r.y,camera.vp.z + r.z,
                camera.vp.x + r.x + camera.vd.x,
                camera.vp.y + r.y + camera.vd.y,
                camera.vp.z + r.z + camera.vd.z,
                camera.vu.x,camera.vu.y,camera.vu.z);
      CreateGeometry();

      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      left  = - ratio * wd2 + 0.5 * camera.eyesep * ndfl;
      right =   ratio * wd2 + 0.5 * camera.eyesep * ndfl;
      glFrustum(left,right,bottom,top,camera.near,camera.far);
      if (camera.stereo == DUALSTEREO)
         glViewport(0,0,camera.screenwidth/2,camera.screenheight);
      else
         glViewport(0,0,camera.screenwidth,camera.screenheight);
      glMatrixMode(GL_MODELVIEW);
      glDrawBuffer(GL_BACK_LEFT);
      if (camera.stereo == ACTIVESTEREO)
         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glLoadIdentity();
      gluLookAt(camera.vp.x - r.x,camera.vp.y - r.y,camera.vp.z - r.z,
                camera.vp.x - r.x + camera.vd.x,
                camera.vp.y - r.y + camera.vd.y,
                camera.vp.z - r.z + camera.vd.z,
                camera.vu.x,camera.vu.y,camera.vu.z);
      CreateGeometry();

   } else {

      glMatrixMode(GL_PROJECTION);
      glLoadIdentity();
      glViewport(0,0,camera.screenwidth,camera.screenheight); 
      left  = - ratio * wd2;
      right =   ratio * wd2;
      glFrustum(left,right,bottom,top,camera.near,camera.far);
      glMatrixMode(GL_MODELVIEW);
      glDrawBuffer(GL_BACK_LEFT);
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glLoadIdentity();
      gluLookAt(camera.vp.x,camera.vp.y,camera.vp.z,
                camera.vp.x + camera.vd.x,
                camera.vp.y + camera.vd.y,
                camera.vp.z + camera.vd.z,
                camera.vu.x,camera.vu.y,camera.vu.z);
      CreateGeometry();
   }

Posted: **Sat Sep 08, 2007 10:37 am**

I guess we could make special render targets which swap the target backbuffers. The technique is basically the same as rendering to a render-target-texture, so I guess it would fit in there for best.

Posted: **Sun Sep 09, 2007 2:49 pm**

Hybrid,
I was thinking of changing how Irrlicht renders using OpenGL. Would it not be easier to have Irrlicht render individually to both back buffers? Changing viewpoints may become difficult though. Thoughts? Also, how would you implement your suggestion of having special render targeting to an individual backbuffer?

Thanks

It might be easier to PM

Posted: **Sun Sep 09, 2007 4:12 pm**

You should consult example 13 for RTT. It's basically a technique to render to a texture and use the result in later passes. You're doing basically the same, excpet that bbr is a special backbuffer instead of a texture. Similar to pbuffer, which is the old version of RTT.
You use the RTT by specifying the special texture as render target. If we pass this method a special value we could use predefined targets offered by the driver.
PM is ok, check my website for the addresse (real email

), but if others should be able to give suggestions we should use the forum

Posted: **Sun Sep 09, 2007 4:20 pm**

So FBOs dont use seperate backbuffers? But they can be bigger than the device...

Posted: **Sun Sep 09, 2007 6:20 pm**

The left and right back buffers a re an OpenGL invention for shutter glasses and similar stereoscopic methods. I never read about the internal implementations, the will basically do similar things. But they can be accessed differently by output hardware such as those glasses.

Posted: **Sun Sep 12, 2010 7:30 am**

did somebody found a way to translate the anaglygh code that mybrainisfull post?

Posted: **Sun Sep 12, 2010 8:57 am**

Just use the special render targets for left and right render buffer, that Irrlicht provides since version 1.6 or 1.7

Posted: **Sun Sep 12, 2010 8:25 pm**

did u mean the matrix4 function like buildCameraLookAtMatrixLH?

Posted: **Sun Sep 12, 2010 8:33 pm**

No, you have to set a special render target, which maps to stereo buffers on certain OpenGL cards. This is what was discussed above, and it's available now in Irrlicht.

Posted: **Sun Sep 12, 2010 8:49 pm**

I see
I already look at anaglyph with opengl, that's why I already saw the code above.
but what I want to do its to separate each of view, left and right, in different viewport.
I dont want to use the nvidia stereo drivers
I have 2 small screen, 1 by eye for emulate the 3d vision
but I have some problem for create each cam
in fact, I try to use an array of cam[3], 1 is the main cam like the anaglyh and the left and right cam is each time puch with the good view.
but when I try to use it, the control doesn't work, the left and right dont move (in fact the main cam just wont move).

Posted: **Mon Sep 13, 2010 7:42 am**

stere buffers are an expensive and very special solution. You seem to need only a little cam update mechanism and a proper viewport usage.

Irrlicht Engine

Rendering with OpenGL

Rendering with OpenGL

To add to that