通过找到删除许多if语句的方法来简化代码

I'm having trouble figuring out a good way to structure my code. I am writing a shader in GLSL. I'm using WebGL. So I have a sprite sheet with 22 items. The sheet is 640 X 640. Except for the last each row has 5 sprites. So I used the following code just to test things out.

我无法找到构建代码的好方法。我正在用GLSL写一个着色器。我正在使用WebGL。所以我有一个包含22个项目的精灵表。工作表是640 X 640.除了最后一行,每行有5个精灵。所以我使用下面的代码来测试一下。

float positionInTime = (currentAge / duration);
positionInTime /= 0.04545;
positionInTime = sign(positionInTime)*floor(abs(positionInTime)+0.5);
vec2 TextureCoord = vec2( 0.0, 0.0 );

if ( positionInTime == 22.0) {
   TextureCoord = vec2( 0.0, 0.0 ); 
}
if ( positionInTime == 21.0) {
   TextureCoord = vec2( 0.2, 0.0 ); 
}
if ( positionInTime == 20.0) {
   TextureCoord = vec2( 0.4, 0.0 ); 
}
if ( positionInTime == 19.0) {
   TextureCoord = vec2( 0.6, 0.0 ); 
}
if ( positionInTime == 18.0) {
   TextureCoord = vec2( 0.8, 0.0 ); 
}
if ( positionInTime == 17.0) {
   TextureCoord = vec2( 0.0, 0.2 ); 
}
if ( positionInTime == 16.0) {
   TextureCoord = vec2( 0.2, 0.2 ); 
}
if ( positionInTime == 15.0) {
   TextureCoord = vec2( 0.4, 0.2 ); 
}
if ( positionInTime == 14.0) {
   TextureCoord = vec2( 0.6, 0.2 ); 
}
if ( positionInTime == 13.0) {
   TextureCoord = vec2( 0.8, 0.2 ); 
}
if ( positionInTime == 12.0) {
   TextureCoord = vec2( 0.0, 0.4 ); 
}
if ( positionInTime == 11.0) {
   TextureCoord = vec2( 0.2, 0.4 ); 
}
if ( positionInTime == 10.0) {
   TextureCoord = vec2( 0.4, 0.4 ); 
}
if ( positionInTime == 9.0) {
   TextureCoord = vec2( 0.6, 0.4 ); 
}
if ( positionInTime == 8.0) {
   TextureCoord = vec2( 0.8, 0.4 ); 
}
if ( positionInTime == 7.0) {
   TextureCoord = vec2( 0.0, 0.6 ); 
}
if ( positionInTime == 6.0) {
   TextureCoord = vec2( 0.2, 0.6 ); 
}
if ( positionInTime == 5.0) {
   TextureCoord = vec2( 0.4, 0.6 ); 
}
if ( positionInTime == 4.0) {
   TextureCoord = vec2( 0.6, 0.6 ); 
}
if ( positionInTime == 3.0) {
   TextureCoord = vec2( 0.8, 0.8 ); 
}
if ( positionInTime == 2.0) {
   TextureCoord = vec2( 0.0, 0.8 ); 
}
if ( positionInTime == 1.0) {
   TextureCoord = vec2( 0.2, 0.8 ); 
}

vec2 TextureSize = vec2(.2, .2);
mediump vec2 realTexCoord = TextureCoord + (gl_PointCoord * TextureSize);
vec4 rotatedTexture = texture2D( texture, realTexCoord );
gl_FragColor = rotatedTexture;

}

The code works but I'd like to improve upon it. It seems like these if states could be greatly simplified by a for loop. Any one have any ideas? Or if 2 variables could be created for TextureCoord x and y that would be great.

代码有效,但我想改进它。似乎这些状态可以通过for循环大大简化。有人有主意吗?或者,如果可以为TextureCoord x和y创建2个变量,那将是很好的。

2 个解决方案

#1

If you can change to a simple pattern of 5x5, this will calculate it in Javascript:

如果您可以更改为5x5的简单模式,则会在Javascript中计算它:

var x = ((25 - positionInTime) % 5) / 5.0;
var y = Math.floor((25 - positionInTime) / 5) / 10.0;
TextureCoord = vec2(x, y);

If not, you can use:

如果没有,您可以使用:

if (positionInTime > 22) {
    var x = 0;
    var y = 0;
if (positionInTime > 7) {
    x = ((22 - positionInTime) % 5) / 5.0;
    y = Math.floor((22 - positionInTime) / 5) / 10.0;
} else {
    x = ((7 - positionInTime) % 4) / 5.0;
    y = Math.floor((7 - positionInTime) / 5) / 10.0;
}
TextureCoord = vec2(x, y);

#2

You can create array of vec2 and use rounded positionInTime as index of this array without loop.

您可以创建vec2数组并使用舍入的positionInTime作为此数组的索引而不使用循环。

You can also to calculate each vector, but if values have regularity. The following code is in doubt:

您还可以计算每个向量,但是如果值具有规律性。以下代码存在疑问:

if ( positionInTime == 7.0) {
   TextureCoord = vec2( 0.0, 0.6 ); 
}
if ( positionInTime == 6.0) {
   TextureCoord = vec2( 0.4, 0.6 ); 
}

I think there is an error (0.4 instead of 0.2).

我认为有一个错误(0.4而不是0.2)。

#1