OpenGL的旋转2D纹理 [英] OpenGL rotating a 2D texture
问题描述
更新
有关更新见底部。
我一直在找了很多在互联网附近，我已经找到了几个教程，解释我想实现，但我无法得到它的工作，无论是教程不完整或不适用我的code。
I've been looking alot around the internet and I have found a few tutorials that explain what I'm trying to achieve but I can't get it to work, either the tutorial is incomplete or not applicable on my code.
我想一些简单的围绕它的原点（中心）旋转2D图像。
I'm trying something as simple as rotating a 2D image around its origin (center).
我用XSTART，XEND，yStart和YEND翻转这是0或纹理1。
I use xStart, xEnd, yStart and yEnd to flip the texture which are either 0 or 1.
这是什么code看起来像
This is what the code looks like
GameRectangle dest = destination;
Vector2 position = dest.getPosition();
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, this->image);
//If the rotation isn't 0 we'll rotate it
if (rotation != 0)
{
glMatrixMode(GL_TEXTURE);
glLoadIdentity();
glTranslatef(0.5, 0.5, 0);
glRotatef(rotation, 0, 0, 1);
glMatrixMode(GL_PROJECTION);
}
glBegin(GL_QUADS);
glTexCoord2d(xStart,yStart);
glVertex2f(position.x, position.y);
glTexCoord2d(xEnd,yStart);
glVertex2f(position.x + this->bounds.getWidth(), position.y);
glTexCoord2d(xEnd,yEnd);
glVertex2f(position.x + this->bounds.getWidth(), position.y + this->bounds.getHeight());
glTexCoord2d(xStart,yEnd);
glVertex2f(position.x, position.y + this->bounds.getHeight());
glEnd();
glDisable(GL_TEXTURE_2D);
//Reset the rotation so next object won't be rotated
glMatrixMode(GL_TEXTURE);
glLoadIdentity();
glRotatef(0, 0, 0, 1);
glMatrixMode(GL_PROJECTION);
这code将图像绘制在它的原始大小，它会旋转，但它会从左上角其裁剪图像很多旋转。通过调用GameRectangle.getOrigin（）我可以轻松地获得了矩形的中心，但我不知道在哪里使用它。
This code will draw the image in it's original size and it will rotate it, but it will rotate it from the top left corner which crops the image a lot. By calling GameRectangle.getOrigin() I can easily get the center of the rectangle, but I don't know where to use it.
位，如果放：
glTranslatef(-0.5, -0.5, 0);
在我所说的：
glRotatef(0.5, 0.5, 0);
这将旋转的中心，但它会STRETCH时的图像，如果它不是一个完美的90度旋转。
It will rotate from the center, but it will strech the image if it's not a perfect 90 degrees rotation.
更新
在试图pretty的太多一切可能，我得到了我一直在寻找的结果。
After trying pretty much everything possible, I got the result I was looking for.
但我不知道这是最好的办法。请告诉我，如果有什么问题我的code。
But I'm not sure if this is the best approach. Please tell me if there's something wrong with my code.
正如我在上面的留言中提到，我使用的是相同的图像多次与不同价值观画出来，所以我无法保存任何实际的图像。所以，我必须每次重置价值我已经呈现后。
As I mentioned in a comment above, I use the same image multiple times and draw it with different values, so I can't save anything to the actual image. So I must reset the values everytime after I have rendered it.
我改变了我的code到这一点：
I changed my code to this:
//Store the position temporary
GameRectangle dest = destination;
Vector2 position = dest.getPosition();
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, this->image);
glTranslatef(dest.getOrigin().x, dest.getOrigin().y, 0);
glRotatef(rotation, 0, 0, 1);
glBegin(GL_QUADS);
glTexCoord2d(xStart,yStart);
glVertex2f(-dest.getWidth()/2, -dest.getHeight()/2);
glTexCoord2d(xEnd,yStart);
glVertex2f(dest.getWidth()/2, -dest.getHeight()/2);
glTexCoord2d(xEnd,yEnd);
glVertex2f(dest.getWidth()/2, dest.getHeight()/2);
glTexCoord2d(xStart,yEnd);
glVertex2f(-dest.getWidth()/2, dest.getHeight()/2);
glEnd();
//Reset the rotation and translation
glRotatef(-rotation,0,0,1);
glTranslatef(-dest.getOrigin().x, -dest.getOrigin().y, 0);
glDisable(GL_TEXTURE_2D);
此旋转纹理连同它的吸入，它不STRETCH时或作物的四边形。然而，边缘有点参差不齐如果图像填充的正方形，但我想我不能避免与出的平滑处理。
This rotates the texture together with the quad it's drawn in, it doesn't strech or crop. However the edges are a bit jagged if the image is filled square but I guess I can't avoid that with out antialiasing.
推荐答案
你需要的是这样的：
glPushMatrix(); //Save the current matrix.
//Change the current matrix.
glTranslatef(dest.getOrigin().x, dest.getOrigin().y, 0);
glRotatef(rotation, 0, 0, 1);
glBegin(GL_QUADS);
glTexCoord2d(xStart,yStart);
glVertex2f(-dest.getWidth()/2, -dest.getHeight()/2);
glTexCoord2d(xEnd,yStart);
glVertex2f(dest.getWidth()/2, -dest.getHeight()/2);
glTexCoord2d(xEnd,yEnd);
glVertex2f(dest.getWidth()/2, dest.getHeight()/2);
glTexCoord2d(xStart,yEnd);
glVertex2f(-dest.getWidth()/2, dest.getHeight()/2);
glEnd();
//Reset the current matrix to the one that was saved.
glPopMatrix();
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