beginner trying to wrap head around a bugged call to GLtranslate

[WillJBD]

I have a archer shooting a arrow. When the archer shoots i need the "camera" to follow the arrow, as to keep the arrow dead center while every thing else translates.

basically follow the arrow.
My code does this to a point, but the arrow somehow gains on the transformation. I don't know how this happens as I set the transformation to position itself where the arrow is positioned.



public void Render(GL10 gl, float deltaTime) {
/************************************************** ************************
* This is where you draw the screen, called every auto Loop pass
* ************************************************** **********************/
//Log.d("Game", "Render");
gl.glViewport(0, 0, Screen.SCREEN_WIDTH, Screen.SCREEN_HEIGHT);
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glOrthof(0, Screen.WIDTH_SCALE, 0, Screen.HEIGHT_SCALE, 1, -1);


gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();

gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);


gl.glEnable(GL10.GL_TEXTURE_2D);
MeshRect mRect; // this holds all of our rectangles


boolean hasTranslated = false;
if (!l2rArrow.isFired) {
gl.glPushMatrix(); //save our state

gl.glTranslatef(l2rArrow.GetToOriginX, l2rArrow.GetToOriginY, 0f); // translate to origin 0,0,0
gl.glRotatef(LBow.getAngle(), 0f, 0f, 1f); //rotate
gl.glTranslatef(-l2rArrow.GetToOriginX, -l2rArrow.GetToOriginY, 0f); // translate to where we want to draw it

texture.bind(gl, Texture.TEXTURE_L2RARROW);
mRect = new MeshRect(l2rArrow.getMyRect());
mRect.Draw(GL10.GL_TRIANGLES, gl);

gl.glPopMatrix(); //return to saved state

} else {
l2rArrow.Update(deltaTime);
texture.bind(gl, Texture.TEXTURE_L2RARROW);
mRect = new MeshRect(l2rArrow.getMyRect());
mRect.Draw(GL10.GL_TRIANGLES, gl);



hasTranslated = true;
gl.glPushMatrix();
gl.glLoadIdentity();
float camX = (float) ((l2rArrow.startX - l2rArrow.PosX));

float camY = (float) ((l2rArrow.startY - l2rArrow.PosY));

if (camY > 0) { camY = 0;}

gl.glTranslatef(camX, camY,0f);


if (l2rArrow.hasCollided) {
//run collision code for detecting a hit and ending turn
}
}
/**================================================ ================================================== =====
* Everything between here should be effected by translate | | gl.gltranslatef(x,y,z) x = Xoffset
*================================================= ================================================== ====*/

// draw translated things
/**================================================ ================================================== =====
* gl.glPopMatrix(); were done go back to normal
*================================================= ================================================== ====*/

if (hasTranslated){
gl.glPopMatrix();
}


}

as i said, the screen follows the arrow, but the arrow seems to gain on the edge of the screen until it runs off it.

[uwi2k2]

hi,

i do not totaly understand what you wanne do with this lines ?:



gl.glTranslatef(l2rArrow.GetToOriginX, l2rArrow.GetToOriginY, 0f); // translate to origin 0,0,0
gl.glRotatef(LBow.getAngle(), 0f, 0f, 1f); //rotate
gl.glTranslatef(-l2rArrow.GetToOriginX, -l2rArrow.GetToOriginY, 0f); // translate to where we want to draw it

and is LBow->Angle changing somewhere els in the script while arow is flying ?

cu
uwi

[WillJBD]

it was my order of operations, needed to look like this


boolean hasTranslated = false;
if (!l2rArrow.isFired) {
gl.glPushMatrix(); //save our state

gl.glTranslatef(l2rArrow.GetToOriginX, l2rArrow.GetToOriginY, 0f); // translate to origin 0,0,0
gl.glRotatef(LBow.getAngle(), 0f, 0f, 1f); //rotate
gl.glTranslatef(-l2rArrow.GetToOriginX, -l2rArrow.GetToOriginY, 0f); // translate to where we want to draw it

texture.bind(gl, Texture.TEXTURE_L2RARROW);
mRect = new MeshRect(l2rArrow.getMyRect());
mRect.Draw(GL10.GL_TRIANGLES, gl);

gl.glPopMatrix(); //return to saved state

} else {
l2rArrow.Update(deltaTime);

hasTranslated = true;
gl.glPushMatrix();
gl.glLoadIdentity();
float camX = (float) ((l2rArrow.startX - l2rArrow.PosX));
//Log.d("cam X =" + Float.toString(camX),"Y=");
float camY = (float) ((l2rArrow.startY - l2rArrow.PosY));
if (camY > 0) { camY = 0;}
if (camX < -4800) { camX = -4800;}

gl.glTranslatef(camX, camY,0f);

texture.bind(gl, Texture.TEXTURE_L2RARROW);
mRect = new MeshRect(l2rArrow.getMyRect());
//Log.d("arrow X =" + Float.toString(l2rArrow.getMyRect().BottomLeftCorn er.x),"Y=");
mRect.Draw(GL10.GL_TRIANGLES, gl);


if (l2rArrow.hasCollided) {
//run collision code for detecting a hit and ending turn
}
}

[WillJBD]

hi,

i do not totaly understand what you wanne do with this lines ?:



and is LBow->Angle changing somewhere els in the script while arow is flying ?

cu
uwi

Yes, before the shot is fired the angle and power of the shot is adjusted by the user drawing a line on the screen. so before the shot that is used to rotate the arrow (and the bow elsewhere in the code) to match the angle of the drawn line.

[uwi2k2]

ok,

sorry i missunderstood this one ...

uwi