opengles抵消纹理坐标的着色器

Question

我使用贴图尔塔斯和这个顶点着色渲染在四纹理：

"uniform mat4 uMVPMatrix;" + 
    "attribute vec4 vPosition;" + 
    "attribute vec4 a_Color;" + 
    "attribute vec2 a_texCoord;" + 
    "varying vec4 v_Color;" + 
    "varying vec2 v_texCoord;" + 
    "uniform vec4 u_newColor;" + 

    "void main() {" + 
    " float offset = 0.33;" + 
    " gl_Position = uMVPMatrix * vPosition;" + 
    " v_texCoord.x = a_texCoord.x + offset;" + 
    " v_texCoord.y = a_texCoord.y + offset;" + 
    " v_Color = u_newColor;" + 
    "}"; 

一切工作正常，我呈现了三分之一，至显示9的一个中间瓦片的纹理在地图集。除了我想'偏移量'是一个变量，即我想根据纹理图集中需要的'瓦片'来改变它。

这怎么可能？

Answer 1

添加均匀，使用：

"uniform mat4 uMVPMatrix;" + 
"attribute vec4 vPosition;" + 
"attribute vec4 a_Color;" + 
"attribute vec2 a_texCoord;" + 
"varying vec4 v_Color;" + 
"varying vec2 v_texCoord;" + 
"uniform vec4 u_newColor;" + 
"uniform vec2 u_offset ;" + //vec2 so there is a x and y component that you can set 

"void main() {" + 
" gl_Position = uMVPMatrix * vPosition;" + 
" v_texCoord = a_texCoord + u_offset;" + 
" v_Color = u_newColor;" + 
"}"; 

，并设置与

glUniform2f(u_offset_location, xTile, yTile);