glsl shader 范围

huan1006

Hi:
首先，我把代码贴上来哈

1. 
   
2. glPushAttrib(GL_ALL_ATTRIB_BITS);
   
3. DrawCubeBox();
   
4. glPopAttrib();
   
5. glEnable(GL_LIGHTING);
   
6. glPushAttrib(GL_ALL_ATTRIB_BITS);
   
7. 
   
8. glActiveTexture(GL_TEXTURE0);
   
9. glBindTexture(GL_TEXTURE_2D, decal);
   
10. glActiveTexture(GL_TEXTURE1);
    
11. glBindTexture(GL_TEXTURE_2D, base);
    
12. glBegin(GL_QUADS);
    
13. glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
    
14. glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f);
    
15. glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 1.0f);
    
16. glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 1.0f);
    
17. glEnd();
    

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我写的shader只希望对四边形有影响；但是最后结果确对DrawCubeBox也有影响啊。怎么将shader范围控制在四边形的范围内呢？后来，我在渲染完四边形后，还贴加了

1. 
   
2. glDeleteObjectARB(v);
   
3. glDeleteObjectARB(p);
   
4. glDetachObjectARB(p, v);
   
5. glDetachObjectARB(p, f);
   

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也没有效果。于是，我就将连接的代码放在前面，结果确是不符合shader效果。片元shader为：

uniform sampler2D TextureUnit0;
uniform sampler2D TextureUnit1;
void main()
{
vec4 value1 = texture2D(TextureUnit0, gl_TexCoord[0]);
vec4 value2 = texture2D(TextureUnit1, gl_TexCoord[1]);
if(tex1.x >= 0.2 && tex1.y >= 0.2 &&
tex1.x <= 0.8 && tex1.y <= 0.8)
gl_FragColor = value2;
else
gl_FragColor = value1;
}

3Q