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tutorial 10 camera code, problem

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#1 sliders_alpha   Members   -  Reputation: 107


Posted 14 April 2012 - 08:13 PM

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"

Posted Image

this is my init

	private void initGL() {
		GL11.glEnable(GL11.GL_TEXTURE_2D);//texture mapping
		GL11.glShadeModel(GL11.GL_SMOOTH);//smooth shading
		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	
		GL11.glLoadIdentity();//reset la matrice de projection
		// Calcul l'aspect ratio de la fenetre
		  (float) displayMode.getWidth() / (float) displayMode.getHeight(),

		  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

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
|Sec Sec Sec <- World line 3
|Sec Sec Sec
|Sec Sec Sec <-World line 1

and a sector is drawed layer by lawer

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


#2 sliders_alpha   Members   -  Reputation: 107


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 :/

#3 Caste   Moderators   -  Reputation: 969


Posted 22 April 2012 - 07:27 AM


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.. :)

#4 sliders_alpha   Members   -  Reputation: 107


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.

#5 Mihai Moldovan   Members   -  Reputation: 127


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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