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sjk

2 Display Lists slower?

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Hi I'm making my first steps in game programming and tried to use display lists for the first time. I hope my code makes at least some sence at all. ;)

For practice I'm making a 2D Jump n Run with a randomly generated world. My problem is that if I use more than one display list my fps start to drop. But with one list they improve. I'm using Java with lwjgl.


The world is saved into a 2D array:

public static void generate() {

//generate random world
for (int col = 0; col < cols; col++) {
for (int row = 12; row < rows; row++) {
a[col][row]= (int) (Math.random()*3);
}
}

//print world array to console
for (int i =0; i < rows; i++) {
for (int j = 0; j < cols; j++) {
System.out.print(" " + a[j]);
}
System.out.println("");
}
}


public static void init() {
// print world
for (int col = 0; col < cols; col++) {
for (int row = 6; row < rows; row++) {
if(a[col][row]== 0) Blocks.loadSky(col,row); //why load sky?
if(a[col][row]== 1) Blocks.loadDirt(col,row);
if(a[col][row]== 2) Blocks.loadRock(col,row);
}
}
}


"generate()" generates the world at start and "init()" runs in my game loop and draws the world.

I commented out my first approach without display lists. I had around 1400 fps at that time.
Then I created only the dirt display list and my fps jumped up to 2700. (when the fps were 2700 the rocks were also rendering just without the list)
But after I implemented my rock display list the fps dropped to 1500.

static int scale = 32;
static int dirt;
static int rock;


//compile() compiles all block types which are later called by loadDirt etc...
public static void compile() {


//number of lists:
dirt = glGenLists(2);

//dirt block
glNewList(dirt, GL_COMPILE);
textureLoader.dirt.bind();
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2f(-16,-16);
glTexCoord2f(1.0f,0);
glVertex2f(-16,16);
glTexCoord2f(1.0f,1.0f);
glVertex2f(16,16);
glTexCoord2f(0,1.0f);
glVertex2f(16,-16);
glEnd();
glEndList();


rock = dirt+1;

glNewList(rock, GL_COMPILE);
textureLoader.rock.bind();
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2f(-16,-16);
glTexCoord2f(1.0f,0);
glVertex2f(-16,16);
glTexCoord2f(1.0f,1.0f);
glVertex2f(16,16);
glTexCoord2f(0,1.0f);
glVertex2f(16,-16);
glEnd();
glEndList();
}


public static void loadDirt(int col, int row) {
/*
textureLoader.dirt.bind();
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2f(scale * col - scale/2,scale * row - scale/2);
glTexCoord2f(1.0f,0);
glVertex2f(scale * col - scale/2,scale * row + scale/2);
glTexCoord2f(1.0f,1.0f);
glVertex2f(scale * col + scale/2,scale * row + scale/2);
glTexCoord2f(0,1.0f);
glVertex2f(scale * col + scale/2,scale * row - scale/2);
glEnd();*/


//store current Matrix
glPushMatrix();

//col and row change all the time => find save format to save the world
//System.out.println(col);

//move block in position
glTranslatef((scale*col),(scale*row),0);

//call dirt list
glCallList(dirt);

//restore old Matrix
glPopMatrix();

}

public static void loadRock(int col, int row) {
/*
textureLoader.rock.bind();
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2f(scale * col - scale/2,scale * row - scale/2);
glTexCoord2f(1.0f,0);
glVertex2f(scale * col - scale/2,scale * row + scale/2);
glTexCoord2f(1.0f,1.0f);
glVertex2f(scale * col + scale/2,scale * row + scale/2);
glTexCoord2f(0,1.0f);
glVertex2f(scale * col + scale/2,scale * row - scale/2);
glEnd();*/


glPushMatrix();
glTranslatef((scale*col),(scale*row),0);
glCallList(rock);
glPopMatrix();
}

public static void loadSky(int col, int row) {

}



What I don't understand is, why is the game running faster with one list which creates only the dirt but is almost as slow as before if I use almost the same one for the rock?
Let me know if you need any more information and I hope that makes sense at all.
Thanks!



And how can I post my code an keep its format? Would probably be better to read. Edited by sjk

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And how can I post my code an keep its format? Would probably be better to read.

If your code uses the tab character for indentation, it will get lost when you post it on GameDev.net. What I have to do is copy my code into Notepad++, then search and replace all tabs with 4 spaces. Then copy and paste that into GameDev.

As for your question, I have another question. I'll admit it doesn't answer your question. Why are you using the old, deprecated way of rendering in OpenGL instead of using the modern way (through using shaders and the like)?

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Ha! Thank you so much that code looks much better now!

As for why I'm using no shaders, I'm just starting out and haven't come that far yet. If you could point me in the right direction I would appreciate. it ;)

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Ha! Thank you so much that code looks much better now!

Yes it does :)


As for why I'm using no shaders, I'm just starting out and haven't come that far yet. If you could point me in the right direction I would appreciate. it ;)

To be honest, I'm not sure of any particularly good online resources to learn about shaders. I remember I always wanted to, but it wasn't until I took a computer graphics course at my university and could actually have things properly explained to me in detail and ask questions that I really started to understand it. For what it's worth, my instructor posted all the class slides and recordings of the lectures online at the class page. If I were you, I'd watch the lecture videos, starting at Lecture 15, Hardware Acceleration. The instructor programmed in C, and he uses some matrix code he wrote earlier in the class sometimes, but it should hopefully be fairly straight forward to translate it into Java. I've never used OpenGL in Java though so I'm afraid I'm no help with lwjgl.

[edit]

But if diving into shaders is detrimental to your motivation, just stick with rendering in immediate mode as you are (in which case I'm no help with your display list problem). Edited by Cornstalks

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Your link to the recordings of the lectures looks really interesting I'll definitely save that. I also want to get into shaders but already figured it would be good to learn the fundamentals first.

Like finding out what my display lists are up to. :) Edited by sjk

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Your link to the recordings of the lectures looks really interesting I'll definitely save that. I also want to get into shaders but already figured it would be good to learn the fundamentals first.

Like finding out what my display lists are up to. :)


That is a problem with the legacy way of OpenGL. Much of what you learn is no longer valid, and your program is going to be very hard to update or reuse to the new ways. I usually recommend the following tutorial: http://www.arcsynthesis.org/gltut/. It is the best I have seen so far, and it also teach you the basics of 3D programming.

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Wow thanks! That's a pretty nice tutorial. I guess I have a lot of reading to do. :)

If anyone knows something about the display lists I would still appreciate it!

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