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## tutorial 10 camera code, problem

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### #1sliders_alpha  Members

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Posted 14 April 2012 - 08:13 PM

Hi,
I used the tutorial 10 camera code in one of my project, as I started OpenGL 3 days ago I'm not sure about my Opengl INIT.

my problem is the following, if I only do translation or Y rotation everything looks fine.
But as soon as I do X rotation my sector get "seprarated"

this is my init

private void initGL() {

GL11.glEnable(GL11.GL_TEXTURE_2D);//texture mapping
GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//couleur de fond noire
GL11.glClearDepth(1.0);//setup du buffer de profondeur
GL11.glEnable(GL11.GL_DEPTH_TEST);//permet le test de profondeur
GL11.glDepthFunc(GL11.GL_LEQUAL); //le type de test de profondeur a faire
GL11.glMatrixMode(GL11.GL_PROJECTION);//selectrione la matrice de projection
// Calcul l'aspect ratio de la fenetre
GLU.gluPerspective(
45.0f,
(float) displayMode.getWidth() / (float) displayMode.getHeight(),
0.1f,
100.0f);

GL11.glMatrixMode(GL11.GL_MODELVIEW);//selectionne la modelview Matrix
GL11.glColor4f(1.0f,1.0f,1.0f,0.3f);			  // Full luminosité, 30% Alpha
GL11.glBlendFunc(GL11.GL_SRC_ALPHA,GL11.GL_ONE);	  // Blending mode one
// met les melleur parametre
GL11.glHint(GL11.GL_PERSPECTIVE_CORRECTION_HINT, GL11.GL_NICEST);
}


any problem in it? (projection mode or something)

as for the rendering algorythm, I don't think that there is any problem with it.
it's quite simple.

I made a function that draw cube where I want (from the current position).
I have 16x256x16 sectors containing 65k cubes
a world is 9x9 sectors large.

I draw the world line by line

world top view
-z
^
|Sec Sec Sec <- World line 3
|Sec Sec Sec
|Sec Sec Sec <-World line 1
|------------------------>x

and a sector is drawed layer by lawer

GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
GL11.glRotatef(lookupdown,1.0f,0.0f,0.0f);
GL11.glRotatef(sceneroty,0.0f,1.0f,0.0f);
GL11.glTranslatef(xtrans, ytrans, ztrans);   //starting position

//drawing each sector
for (int zsect=0 ; zsect < displayArea; zsect++)
{
for (int xsect=0 ; xsect < displayArea; xsect++){
chunk = world.getSector((short)xsect, (short)zsect);
//drawing each layer
for(int yc=0; yc<256; yc++){
for(int zc=0; zc<16;zc++){
for(int xc=0; xc<16; xc++){

chunk.drawCube(xc.yc.zc,0.5f) //0.5f is a x translation
}
GL11.glTranslatef(-16.0f, 0.0f, 1.0f); //goes where line+1 of the layer is starting
}
GL11.glTranslatef(0.0f, 1.0f, -16.0f); //goes where layer+1 is starting
}
GL11.glTranslatef(16.0f, -256.0f, 0.0f); //goes where the next chunk on the line is starting
}
GL11.glTranslatef(-(float)(displayArea*16.0f), 0.0f, 16.0f);//goes at the beginning of the next chunk line
}



video examples, chunk generation :

world generation

any idea?

thanks =D

### #2sliders_alpha  Members

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Posted 15 April 2012 - 04:12 AM

after several hours af tweaking I am still unsuccessful.

however since each chunk is drawed perfectly and the problem occurs just betwen them, I think the problem here is mathematical precision.

indeed, each chunk is drawed layer by layer, the cursor is only moved from 1f on Y betwen each layer.
but when you want to draw the next chunk you need to get down from 256f on Y.

since the camera is using sin, cos, a precalculation of 1/180*pi may be, a slight offset appears and screw with my grid positioning.

I don't really see how to solve that :/

### #3Caste  Members

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Posted 22 April 2012 - 07:27 AM

Hi,

I think the problem is the 1.0f in your glTranslatef calls. Remember that glTranslatef will translate your whole scene about the vector your plug in, and by calling it several times these translations are accumulated. So if you want to stay on one of your grid lines, you just advance x or z by 16, but leave all others 0.

Hope that helps even though we kept you waiting so long..

### #4sliders_alpha  Members

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Posted 30 April 2012 - 06:31 AM

thanks for your awnser, but I still don't get it =p

I have to make some 1.0f translation, because once the first layer of the chunk is displayed I have to draw the next one, wich is 1.0f above.

### #5Mihai Moldovan  Members

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Posted 30 April 2012 - 06:54 PM

Look into using the built-in matrix stack, specifically glPushMatrix, glLoadIdentity and glPopMatrix.

This will allow you to keep your transforms from interfering with eachother (transforms from other objects).

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