Develop Reference

glRotatef works on multiple objects

Basicly I want to open a Door and I thought of using glRotatef.
My Problem is that it is affecting every object which is drawn after it.
Does anyone know how to stop that ?
Door.class
public static void draw(Texture door) {
door.bind();
if(Door_Test.state == "out" && d != 90){
glRotatef(i, 0, 1, 0);
i+=5;
}
glBegin(GL_QUADS);
glColor3f(1f, 1f, 1f);glTexCoord2f(0,0);glVertex3f(-2,3, -15);
glColor3f(1f, 1f, 1f);glTexCoord2f(0,1);glVertex3f(-2,-3, -15);
glColor3f(1f, 1f, 1f);glTexCoord2f(1,1);glVertex3f(2,-3, -15);
glColor3f(1f, 1f, 1f);glTexCoord2f(1,0);glVertex3f(2,3, -15);
glEnd();
}

Common way to do it:
glPushMatrix();
glRotatef(/*...*/);
// Drawing commands here
glPopMatrix();

When you rotate, it rotates the entire scene. So to rotate a single object, you rotate the entire scene, draw your object, then rotate your screen back.
glRotatef(i, 0, 1, 0);
// Draw object.
glRotatef(-i, 0, 1, 0);
As Reto Koradi pointed out, if you continually do this you might have floating point rounding errors that accumulate over time. HolyBlackCat's answer offers a better solution.

trouble with slick 2d unicode font

ok so I have determined that if I change my orthographic matrix coordinate system to
GL11.glOrtho(0, Strings.DISPLAY_WIDTH, Strings.DISPLAY_HEIGHT, 0, -1, 1);
instead of this
GL11.glOrtho(0, Strings.DISPLAY_WIDTH, 0, Strings.DISPLAY_HEIGHT, -1, 1);
I can draw strings with slick right side up however the game im building uses this system
GL11.glOrtho(0, Strings.DISPLAY_WIDTH, 0, Strings.DISPLAY_HEIGHT, -1, 1);
and slick draws things with the top of the matrix being 0 and the bottom being the height of the display is there anyway I can rotate or draw the strings differently without having to change my games coordinate system?
here is my string drawing class
private Font javaFont;
private UnicodeFont uniFont;
public TextHandler(int letterSize) {
this.initHandler(letterSize);
}
private void initHandler(int size) {
this.javaFont = new Font("Times New Roman", Font.BOLD, size);
this.uniFont = new UnicodeFont(this.javaFont);
this.uniFont.getEffects().add(new ColorEffect(java.awt.Color.white));
this.uniFont.addAsciiGlyphs();
try {
this.uniFont.loadGlyphs();
} catch (SlickException e) {
e.printStackTrace();
}
}
public void drawString(String string, float x, float y) {
this.uniFont.drawString(x, y, string, Color.white);
}
and my openGl initialization code if it helps
GL11.glMatrixMode(GL11.GL_PROJECTION);
GL11.glLoadIdentity();
GL11.glOrtho(0, Strings.DISPLAY_WIDTH, 0, Strings.DISPLAY_HEIGHT, -1, 1);
GL11.glMatrixMode(GL11.GL_MODELVIEW);
GL11.glEnable(GL11.GL_TEXTURE_2D);
GL11.glClearColor(0, 0, 1, 0);
GL11.glDisable(GL11.GL_DEPTH_TEST);

Yes, you could set up a rendering system where the first glOrtho call sets up the Slick rendering, and then you render the strings. Then you call glOrtho again, but render the rest of your game. glOrtho simply tells OpenGL to setup an orthographic projection, and what corner of the screen to start rendering from. Slick uses the top left hand corner whereas you are using the bottom left hand corner. OpenGL is a state based machine, so you must render the Slick stuff, switch to the new projection, and then render the rest of your game.
You also don't need that call to glDisable(GL_DEPTH_TEST);. Depth testing is turned off by default.

LWJGL/OpenGL scaling textures weirdly

I am making a platformer which I started developing with default java functions, but now am switching to OpenGL for everything. I have done everything like I always do with OpenGL, and what I did works fine in my other OpenGL projects. Now my problem is that LWJGL/OpenGL is scaling my textures in a very strange way.
It seems to be related to my screen's aspect ratio. (8:5)
I already had to flip the screen to make it the right way round, but as you can see the text is working fine, it's just the textured rect, and it isn't even straight on the bottom.
Here are the most important snippets from the two classes which actually use OpenGL:
Metamorph.java (main class)
public static void initGL()
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, Display.getWidth(), 0, Display.getHeight(), 1, -1);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glMatrixMode(GL_MODELVIEW);
glClearColor(0, 0, 0, 1);
glDisable(GL_DEPTH_TEST);
}
public void render()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glScalef(1.0f, -1.0f, 1.0f);
glTranslatef(0f, -720f, 0f);
//glScalef(1280f/800, 720f/500, 1f);
renderer.render();
Display.update();
Display.sync(60);
}
Renderer.java (rendering stuff)
private void renderMainMenuWithGL()
{
//System.out.println("Main Menu!");
glColor4f(1, 1, 1, 1);
try
{
Texture bg = loadTexture("mockery");
bg.bind();
} catch (Exception e)
{
e.printStackTrace();
}
//drawQuad(0, 0, 1280, 720, 0, 0, 1280, 720);
glPushMatrix();
{
glBegin(GL_QUADS);
glTexCoord2f(0, 0);glVertex2f(0, 0);
glTexCoord2f(0, 1);glVertex2f(0, 720);
glTexCoord2f(1, 1);glVertex2f(1280, 720);
glTexCoord2f(1, 0);glVertex2f(1280, 0);
glEnd();
}
glPopMatrix();
TrueTypeFont f = loadFont(MAINFONT, Font.PLAIN, 50);
TrueTypeFont fb = loadFont(MAINFONT, Font.PLAIN, 48);
int sel = -1;
if(Mouse.getX() > 1000 && Mouse.getX() < 1240 && Mouse.getY() > 282.5F && Mouse.getY()< 737.5F)
sel = Math.round((Mouse.getY() - 337.5F)/75F);
if(sel == 0)
drawStringRight(fb, 1240, 350, "Story", new Color(0xff516b6b));
else
drawStringRight(f, 1240, 350, "Story", new Color(0xff516b6b));
}
private void drawStringRight(TrueTypeFont f, int x, int y, String s, Color c)
{
glPushMatrix();
f.drawString(x-f.getWidth(s), y, s, c);
glPopMatrix();
}
I am also open to advice on file structure/what I did wrong elsewhere, but keep in mind this is heavily WIP

The only possible problem I can see from what you have posted is the scaling and translating you are doing prior to rendering. You should not need to do this with your projection matrix setup the way it is. Other possibilities are that either the dimensions are not really 1280x720 as you think or you have modified one of the matrices further in the code you have not posted. I would try setting both the modelview and projection matrices to the identity matrix and then use glOrtho as you have above immediatly before drawing your quad, and use Display.getWidth and Display.getHeight instead of 1280/720 for the vertex coords.
This works fine for me:
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, Display.getWidth(), 0, Display.getHeight(), 1, -1);
glBegin(GL_QUADS);
glTexCoord2f(0,0);
glVertex2i(0, 0);
glTexCoord2f(1,0);
glVertex2i(Display.getWidth(), 0);
glTexCoord2f(1,1);
glVertex2i(Display.getWidth(), Display.getHeight());
glTexCoord2f(0,1);
glVertex2i(0, Display.getHeight());
glEnd();
If this still doesnt work, make sure that the viewport is also set to the entire display: glViewport(0,0,Display.getWidth(),Display.getHeight()).
Aswell, I notice that you are using glPushMatrix() and glPopMatrix before and after drawing, which does nothing and is not needed. Push and pop are used to save the current projection or modelview matrix and then reload it later, so that you can apply transformations inbetween and undo them when needed.

You're setting the projection matrix such that the coordinates of the corners of the window are (0,0) through (1680, 1050), and those are mapped into an area that covers 1280x800 pixels. Then you're drawing a 1280x720 image into it, so the screen coordinates of the image come out to span only 800x500 pixels. If you use 1280x720 in your glOrtho() call, I believe it will fix the issue. That is, you want the size of the window, not the size of the display in that call.

Drawing transparent ShapeRenderer in libgdx

I have a drawn a filled circle using ShapeRenderer and now I want to draw this circle as a transparent one. I am using the following code to do that: But the circle is not coming as transparent. Also, I checked th libgdx API and from the wiki, it says that, need to Create CameraStrategy. Has somebody faced similar issue ever before? If so, please give me some clues. Thanks in advance.
Gdx.gl.glEnable(GL10.GL_BLEND);
Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
drawFilledCircle();
Gdx.gl.glDisable(GL10.GL_BLEND);
private void drawFilledCircle(){
shapeRenderer.setProjectionMatrix(camera.combined);
shapeRenderer.begin(ShapeType.FilledCircle);
shapeRenderer.setColor(new Color(0, 1, 0, 1));
shapeRenderer.filledCircle(470, 45, 10);
shapeRenderer.end();
}

The following code is working for me in this case, maybe it will help someone else:
Gdx.gl.glEnable(GL10.GL_BLEND);
Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
shapeRenderer.setProjectionMatrix(camera.combined);
shapeRenderer.begin(ShapeType.FilledCircle);
shapeRenderer.setColor(new Color(0, 1, 0, 0.5f));
shapeRenderer.filledCircle(470, 45, 10);
shapeRenderer.end();
Gdx.gl.glDisable(GL10.GL_BLEND);

First we need to enable blending:
Gdx.gl.glEnable(GL10.GL_BLEND);
And make sure that you don't call SpriteBatch.begin() and SpriteBatch.end() between that line of code and your Shaperender.drawSomething() line of code. I don't know why but that's what works in my case

Only this worked for me :
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);
//Gdx.gl.glEnable(GL20.GL_BLEND);
Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA); // <<< this line here makes the magic we're after
game.shapeRenderer.setProjectionMatrix(camera.combined);
game.shapeRenderer.begin(ShapeType.Filled);
go.drawShapes();
game.shapeRenderer.end();
//Gdx.gl.glDisable(GL20.GL_BLEND);

Well, there is not really a point in drawing something fully transparent. If you did want to make a half transparent circle, you would have to clear the color buffer by glClearColor before each frame and set Color alpha component to 0.5f.
If you wouldn't clear the buffer, after few render draws, the circle would blend into one with almost solid color.
private void drawFilledCircle(Camera camera){
Gdx.gl.glClearColor(0, 0, 0, 0);
Gdx.gl.glClear( GL10.GL_COLOR_BUFFER_BIT );
shapeRenderer.setProjectionMatrix(camera.combined);
shapeRenderer.begin(ShapeType.FilledCircle);
shapeRenderer.setColor(new Color(0, 1, 0, 0.5f)); // last argument is alpha channel
shapeRenderer.filledCircle(470, 45, 10);
shapeRenderer.end();
}

OpenGL matrix not rotating properly

Alright, so I got this code for gluLookAt:
lookAt = new Vector3f(-player.pos.x, -player.pos.y, -player.pos.z);
lookAt.x += (float)Math.cos(Math.toRadians(player.yaw)) * Math.cos(Math.toRadians(player.pitch));
lookAt.y += (float)Math.sin(Math.toRadians(player.pitch));
lookAt.z += (float) Math.sin(Math.toRadians(player.yaw)) * Math.cos(Math.toRadians(player.pitch));
GLU.gluLookAt(-player.pos.x, -player.pos.y, -player.pos.z,
lookAt.x, lookAt.y, lookAt.z,
0, 1, 0);
And when I try to draw a rotated cube it does not rotate properly.
GL11.glPushMatrix();
GL11.glLoadIdentity();
GL11.glTranslatef(-cube.pos.x, -cube.pos.y, -cube.pos.z);
GL11.glRotatef(cube.yaw, 0, 1, 0);
GL11.glTranslatef(cube.pos.x, cube.pos.y, cube.pos.z);
/*draw the cube normally*/
GL11.glPopMatrix();
So my question is am I handling the alterations to the matrix done by glulookat properly? or am I doing somethign wrong? The result I am looking for is to return the cube to 0,0,0 and rotate it, then put it back where it was.

problem is here:
GL11.glTranslatef(-cube.pos.x, -cube.pos.y, -cube.pos.z);
GL11.glRotatef(cube.yaw, 0, 1, 0);
GL11.glTranslatef(cube.pos.x, cube.pos.y, cube.pos.z);
The cube is already 'at' 0,0,0. This is because the Medel matrix is identity (as you called glLoadIdentity()).
so you should do:
GL11.glRotatef(cube.yaw, 0, 1, 0);
GL11.glTranslatef(cube.pos.x, cube.pos.y, cube.pos.z);
which should have the desired effect. If not, try it with a fixed camera to see if the code you added before glulookat() is causing the lookat target to be too far away from 0,0,0 (where your cube is)

Calling glLoadIdentity before drawing your cube will wipe out whatever gluLookAt has setup in your view matrix, I don't think it should be there.