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[SOLVED] OpenGL Sprite sheet clipping problem
Posted: Fri Aug 09, 2013 8:54 am
by 0x0000000
Hi everyone, its been a while since I have posted here, mostly because of school.
But I have ran into another problem in my game engine development.
This is the problem:
When I load a *small* sprite sheet in OpenGL, for example 64x64 with 4 tiles each 32x32, the sprite clipping works fine,
but when I try to load a large sprite sheet, for example 512x512, it doesn't clip the sprite properly.
This is my code:
Code: Select all
void spritesheet::render() {
const float tw = float(size.getX()) / float(getTexture().w());
const float th = float(size.getY()) / float(getTexture().h());
numPerRow = getTexture().w() / size.getX();
const float tx = (m_frameIndex % numPerRow) * tw;
const float ty = (m_frameIndex / numPerRow + 1) * th;
texture.setCurrent();
glBegin(GL_QUADS);
glTexCoord2f(tx, ty + th); glVertex3f((float)pos.getX(), (float)pos.getY(), 0);
glTexCoord2f(tx + tw, ty + th); glVertex3f((float)pos.getX() + (float)size.getX(), (float)pos.getY(), 0);
glTexCoord2f(tx + tw, ty); glVertex3f((float)pos.getX() + (float)size.getX(), (float)pos.getY() + (float)size.getY(), 0);
glTexCoord2f(tx, ty); glVertex3f((float)pos.getX(), (float)pos.getY() + (float)size.getY(), 0);
glEnd();
}
If someone could at least tell me what is wrong I would be greatful, because I still can't figure it out.
[EDIT] Hi guys I've figured it out:
Code: Select all
void spritesheet::render() {
tile t;
t.numX = 4;
t.numY = 0;
t.w = 32.f / 512.f;
t.h = 32.f / 512.f;
GLfloat y = (16 - t.numY) * t.h;
GLfloat x = (t.w * t.numX);
texture.setCurrent();
glBegin(GL_QUADS);
glTexCoord2f(x, y); glVertex3f((float)pos.getX(), (float)pos.getY(), 0);
glTexCoord2f(x + t.w, y); glVertex3f((float)pos.getX() + (float)size.getX(), (float)pos.getY(), 0);
glTexCoord2f(x + t.w, y - t.h); glVertex3f((float)pos.getX() + (float)size.getX(), (float)pos.getY() + (float)size.getY(), 0);
glTexCoord2f(x, y - t.h); glVertex3f((float)pos.getX(), (float)pos.getY() + (float)size.getY(), 0);
glEnd();
}
Code: Select all
struct tile {
GLfloat numX;
GLfloat numY;
GLfloat w;
GLfloat h;
};
Thanks for trying to help me dandymcgee
Re: OpenGL Sprite sheet clipping problem
Posted: Fri Aug 09, 2013 5:44 pm
by dandymcgee
Are you sure it's exactly 512x512, or some other powers of 2?
Re: OpenGL Sprite sheet clipping problem
Posted: Fri Aug 09, 2013 6:25 pm
by 0x0000000
dandymcgee wrote:Are you sure it's exactly 512x512, or some other powers of 2?
Yes, I'm sure. I've checked everything but I still cant figure it out. I've just begun learning OpenGL the past few days so I probably
just screwed up something in my code. Anyways, thanks for the reply!
Re: OpenGL Sprite sheet clipping problem
Posted: Fri Aug 09, 2013 6:51 pm
by 0x0000000
I'm not sure if this is the problem but, if I set m_frameIndex to zero, which I always have been, then it would be 0 % numPerRow.
I am going to change the frame index to see if it helps.
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Sun Aug 11, 2013 9:06 am
by dandymcgee
0x0000000 wrote:I'm not sure if this is the problem but, if I set m_frameIndex to zero, which I always have been, then it would be 0 % numPerRow.
I am going to change the frame index to see if it helps.
So was this the problem?
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Sun Aug 11, 2013 10:06 am
by 0x0000000
dandymcgee wrote:0x0000000 wrote:I'm not sure if this is the problem but, if I set m_frameIndex to zero, which I always have been, then it would be 0 % numPerRow.
I am going to change the frame index to see if it helps.
So was this the problem?
I can't be 100% sure that this was the problem, due to the fact that I didn't have the balls to make my own code for the function, the entire texture size/clipping thing was just something I found off StackExchange
, the reason I posted it here was because I couldn't figure out why it was working on small sheets and not large ones.
Please don't ban me
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Sun Aug 11, 2013 6:24 pm
by dandymcgee
Hey.. copy/pasta is how I learned. LazyFoo, 'nuff said. No hate.
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Mon Aug 12, 2013 3:02 am
by K-Bal
It could help to write unit tests. That way you can be sure that your numbers are right.
Re: [SOLVED-ish] OpenGL Sprite sheet clipping problem
Posted: Thu Aug 22, 2013 1:51 pm
by 0x0000000
Hello again guys, I'm sorry if I shouldn't revive this topic but I didn't
think it would be necessary to open another one for problems related to this.
In the solution I posted above, I made it so that if you wanted to select a tile,
you would have to give it a numX and numY, instead of just tileNum.
I've noticed that in the Elysian Shadows engine that the tiles are handled with just the
tile index, and I would like to understand how to do this.
Any help would be greatly appreciated
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Thu Aug 22, 2013 5:26 pm
by dandymcgee
I usually do this:
Tile *tile = tileArray[(y * tilesPerRow) + x];
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Fri Aug 23, 2013 12:49 am
by 0x0000000
dandymcgee wrote:I usually do this:
Tile *tile = tileArray[(y * tilesPerRow) + x];
I don't have a tile array but I figured it out;
Code: Select all
/*
Draws a textured quad that
is clipped like a spritesheet
*/
void khDrawClippedTexturedQuad(GLuint texture, float x, float y, float w, float h, float a, int cw, int ch, int tw, int th, int num) {
GLfloat nx = (float)(num % (tw / cw));
GLfloat ny = (float)(num / (th / ch));
GLfloat tcw = (float)cw / (float)tw;
GLfloat tch = (float)ch / (float)th;
GLfloat tx = (tcw * nx);
GLfloat ty = (th / ch - ny) * tch;
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glLoadIdentity();
glPushMatrix();
glTranslatef(x + w/2, y + h/2, 0);
glRotatef(a, 0, 0, 1);
if(!glIsTexture(texture)) {
glBindTexture(GL_TEXTURE_2D, texture);
}
glBegin(GL_QUADS);
glColor3f(1.0, 1.0, 1.0);
glTexCoord2d(tx, ty);
glVertex3f(-(w/2), -(h/2), 0);
glTexCoord2d(tx + tcw, ty);
glVertex3f(w/2, -(h/2), 0);
glTexCoord2d(tx + tcw, ty - tch);
glVertex3f(w/2, h/2, 0);
glTexCoord2d(tx, ty - tch);
glVertex3f(-(w/2), h/2, 0);
glEnd();
glPopMatrix();
}
Thanks for the help dandymcgee!
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Fri Aug 23, 2013 7:51 am
by dandymcgee
0x0000000 wrote:dandymcgee wrote:I usually do this:
Tile *tile = tileArray[(y * tilesPerRow) + x];
I don't have a tile array but I figured it out;
Code: Select all
/*
Draws a textured quad that
is clipped like a spritesheet
*/
void khDrawClippedTexturedQuad(GLuint texture, float x, float y, float w, float h, float a, int cw, int ch, int tw, int th, int num) {
GLfloat nx = (float)(num % (tw / cw));
GLfloat ny = (float)(num / (th / ch));
GLfloat tcw = (float)cw / (float)tw;
GLfloat tch = (float)ch / (float)th;
GLfloat tx = (tcw * nx);
GLfloat ty = (th / ch - ny) * tch;
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glLoadIdentity();
glPushMatrix();
glTranslatef(x + w/2, y + h/2, 0);
glRotatef(a, 0, 0, 1);
if(!glIsTexture(texture)) {
glBindTexture(GL_TEXTURE_2D, texture);
}
glBegin(GL_QUADS);
glColor3f(1.0, 1.0, 1.0);
glTexCoord2d(tx, ty);
glVertex3f(-(w/2), -(h/2), 0);
glTexCoord2d(tx + tcw, ty);
glVertex3f(w/2, -(h/2), 0);
glTexCoord2d(tx + tcw, ty - tch);
glVertex3f(w/2, h/2, 0);
glTexCoord2d(tx, ty - tch);
glVertex3f(-(w/2), h/2, 0);
glEnd();
glPopMatrix();
}
Ah, right. Same concept applies to clipping a sheet as you've already discovered. Thanks for posting the code instead of just saying, "Nevermind, I fixed it."
0x0000000 wrote:Thanks for the help dandymcgee!
You're welcome. It's what we're here for.
Re: [SOLVED] OpenGL Sprite sheet clipping problem
Posted: Sat Aug 24, 2013 7:14 am
by bbguimaraes
dandymcgee wrote:Thanks for posting the code instead of just saying, "Nevermind, I fixed it."
http://xkcd.com/979/