Simple fbo question

OpenGL Development
#1

Hello,

Having some obvious problems again with redering.

Im having this terrain:

Now i want to make the water reflective, whats obviously done using an frame buffer object.
The world is build up with chunks, rendering max 4 chunks at the same time.

How should i render to an fbo?

  • Just send the current screen to the fbo, and figure out how it must be transferred to match the right position.
  • Draw every (visible) Chunk to the fbo separately?

Also im ondering how i should transform the view before rendering to an fbo, should i keep the same transformation (excluding rotation), or do i need to transform to the right psition fist (like top view).
Also wat parameters should i use for glClipPlane(GL_CLIP_PLANE0, clipbuffer);

At last im having an overall question about rendering the chunks.
Whem im rendering an whole chunk at once im getting these blending errors:

This is caused because an transparent texture blends with the green background, the chunk behind it is drawn after that.
Is there some solution for this or should i first render all ground, then trees and other objects, then water, like this:


            for(int tx = 0; tx < 3; tx ++){
                for(int ty = 0; ty < 3; ty ++){
                    if(c[tx + ty*3] != null){ 
                        c[tx + ty*3].Draw(); 
                    }
                }
            }
            
            for(int tx = 0; tx < 3; tx ++){
                for(int ty = 0; ty < 3; ty ++){
                    if(c[tx + ty*3] != null){ 
                        c[tx + ty*3].DrawObjects();
                    }
                }
            }
            
            for(int tx = 0; tx < 3; tx ++){
                for(int ty = 0; ty < 3; ty ++){
                    if(c[tx + ty*3] != null){ 
                        c[tx + ty*3].DrawWater(); 
                    }
                }
            }
#2

First you render all opaque geometry, roughly front-to-back, to reduce overdraw.
Then you render all translucent geometry, strictly back-to-front, or it will show artifacts.

#3

Thank you, i was afraid of that, but i thought to ask it first, just to be sure.
And does anyone have an idea about the reflective water?

#4

Really annoying, i dont get this transformation stuff.
Please anyone, im really clueless.

My current try (im not rendering the terrain on top, because the water would otherwise not be visible much):

As visible my problem is the needed transformation, the clip plane is not really working and my textures are only filled with an quarter of the terrain im actually rendering (to the fbo texture).

Code:


     //Fill current fbo's without transformation:

        GL11.glPushMatrix();
            
            TiltWorld();
            for(int tx = 0; tx < 3; tx ++){
                for(int ty = 0; ty < 3; ty ++){
                    if(c[tx + ty*3] != null){ 
                        c[tx + ty*3].PreDraw(); 
                    }
                }
            }
            
        GL11.glPopMatrix();

       //Draw land / water and trees;

PreDraw:


    public void PreDraw(){
        clipbuffer.rewind();
        fbo.Bind();
        //fbo.ClipPlane();
        
        glEnable(GL_CLIP_PLANE0);  
        glClipPlane(GL_CLIP_PLANE0, clipbuffer);  
        glPushMatrix();	  
          
            glTranslatef(-x, 0, -z);
            Draw();
            DrawObjects();
            
        glPopMatrix();
        glDisable(GL_CLIP_PLANE0);  
        
        fbo.Unbind();
    }
    
    private DoubleBuffer clipbuffer = BufferUtils.createDoubleBuffer(4).put(new double[]{ 0, -1, 0, 0.0 });